Are the washout values currently accepted for lesion characterization in dedicated adrenal CT adequate for diagnosis?

PURPOSEWe aimed to investigate the accuracy of density characteristics and washout values of lesions detected on computed tomography (CT) at the cutoff values obtained from the literature by taking the pathological results of adrenalectomy specimens as reference and to determine the cutoff values of parameters evaluated on CT for the differentiation of adenoma and nonadenoma lesions in the study group.METHODSHospital records and standard CT imaging data (noncontrast early phase [65 s] and late phase [15 min] ) of 84 patients with 87 lesions who underwent adrenalectomy between January 2012 and December 2018 were retrospectively reevaluated by two radiologists in consensus. The patients were categorized as having adenoma and nonadenoma lesions according to the pathology results. The sensitivity, specificity and diagnostic accuracy of CT parameters (density values and washout percentages) were evaluated. Differences in the CT parameters (size, noncontrast and early-late enhancement density and absolute and relative washout values) were investigated. The optimal cutoff values of CT parameters were determined by ROC analysis.RESULTSNoncontrast CT had a specificity of 87.75% and 95.9%, sensitivity of 60% and 48.6%, diagnostic accuracy of 77.7% and 89.47% for adenomas, at the cutoff values of ≤10 HU and ≤0 HU, respectively. For absolute washout value ≥ 60%, the sensitivity, specificity and accuracy were 64.7%, 52.38% and 56.75%, respectively; while these rates were 76.47%, 56.52% and 62.16%, respectively, for relative washout value ≥40%. Adenomas and nonadenomas showed significant difference in terms of size (p < 0.0001), unenhanced attenuation (p < 0.0001), relative washout (p = 0.020) and delay enhancement (p < 0.001). But there were no differences in terms of absolute washout (p = 0.230) and early enhancement (p = 0.264). The cutoff values for the differentiation of adenomas and nonadenomas were as follows: size ≤44 mm, noncontrast density <20 HU, early-phase density ≥45 HU, delayed-phase density ≤44 HU, absolute washout 74.83% and relative washout 57.76%.CONCLUSIONThe current washout criteria used in the differentiation of adenoma and nonadenoma lesions in dynamic CT imaging can give false negative and positive results. According to the existing criteria, the most reliable parameter in adenoma–nonadenoma differentiation is ≤ 0 HU noncontrast CT density value.

According to the autopsy studies, adrenal masses are among the most common tumors detected in humans (1). In autopsy series, this prevalence has been reported as 1% to 9.8% (1). With the advances in imaging techniques and their increasing use, there has also been a recent increase in radiologically reported adrenal masses (2–5), varying between 0.35% and 5% for CT examinations (6). Adenomas are the most common adrenal lesions in patients without primary malignancy (1, 7, 8). Although adrenal gland is a common site for distant metastases in patients with known malignancies, adenomas are more common than metastases in these patients. Since the majority of adrenal adenomas are benign and nonfunctional lesions, a clinical and radiological follow-up is sufficient. In nonadenoma lesions, a biopsy or direct surgical resection can be recommended according to the characteristics of the patient. Therefore, determination of whether a detected adrenal mass is an adenoma or nonadenoma is critically important in patient management and changes the form of treatment (9).Computed tomography (CT) is the radiological method of choice in the characterization of adrenal mass lesions (8, 10). Adenomas have low density values in noncontrast CT scans due to their intracytoplasmic fat content (3, 6, 10, 11). However, as much as 30% of adrenal adenomas are poor in fat, thus making it impossible to distinguish them from other masses based on noncontrast CT density (8, 10). In this case, most authors reported that the washout character determined by dynamic contrast-enhanced CT examination differentiates adrenal adenomas from other lesions (10–13). Due to their rich capillary network, adenomas are stained early with the contrast agent, causing them to exhibit a high level of washout (8). However, some nonadenoma lesions, particularly pheochromocytoma, have been reported to show a similar washout pattern (4, 14–18). In the literature, there are many studies that investigated noncontrast and contrast-enhanced CT density and the washout criterion for the differentiation of adenoma and nonadenoma lesions (4, 6, 10–18). However, the scan parameters used in these studies, the characteristics of the devices, the time of wash-in and washout, contrast agent dose, and iodine concentration are not standard and show differences (e.g., 2.5–10 mm collimation; 3–5 mm reconstruction intervals; 80–140 kVp; 150–370 mA; 0.75–3:1 pitch; nonhelical, helical, or multi-slice device; 35–120 s wash-in time; 3–45 min washout time; 100–150 mL contrast agent dose; 300–370 mg/L iodine concentration). In a study using different minutes as washout criteria in the same lesions, different specificity and sensitivity values were found according to the washout time (19). In studies evaluating the effectiveness of adrenal CT in the literature, the reference method also differs. For these reasons, the available literature data is far from being standard. Nonadenoma lesions, which are evaluated as adenoma based on the available data, may cause serious problems in patient management.In the current study, we aimed to investigate the accuracy of density characteristics and washout values of lesions detected on CT at the cutoff values obtained from the literature by taking the pathological results of adrenalectomy specimens as reference to determine the cutoff values of parameters evaluated on CT for the differentiation of adenoma and nonadenoma lesions in the study group.     

Evaluating the added benefit of CT texture analysis on conventional CT analysis to differentiate benign ovarian cysts

PURPOSEWe aimed to evaluate the benefit of adding CT texture analysis on conventional CT features of benign adnexal cystic lesions, especially in identifying mucinous cystadenoma.METHODSThis retrospective study included patients who underwent surgical removal of benign ovarian cysts (44 mucinous cystadenomas, 32 serous cystadenomas, 16 follicular/simple cysts and 43 endometriotic cysts) at our institution between January 2015 and November 2017. The CT images were independently reviewed by an abdominal radiologist (reviewer 1) and a resident (reviewer 2). Both reviewers recorded the conventional characteristics and performed texture analysis. Based on reviewer 1’s results, two decision trees for differential diagnosis were developed. Reviewer 2’s results were then applied to the decision trees. The diagnostic performances of each reviewer with and without the decision trees were compared.RESULTSSeveral conventional features and texture analysis parameters showed significant differences between mucinous cystadenomas and other benign adnexal cysts. The first decision tree selected septum number and thickness as significant features, whereas the second decision tree selected septum number and the mean values at spatial scaling factor (SSF) 0. Reviewer 1’s performance did not change significantly with or without the use of the decision trees. Reviewer 2’s interpretations were significantly less sensitive than reviewer 1’s interpretations (p = 0.001). However, when aided by the first and second decision trees, Reviewer 2’s interpretations were significantly more sensitive than reviewer 1’s interpretations (86.4%, p < 0.001; 72.7%, p = 0.001).CONCLUSIONThis study suggests the benefit of CT texture analysis on conventional images to differentiate mucinous cystadenoma from other benign adnexal cysts, particularly for less experienced radiologists.

In the assessment of a possible adnexal mass, it is paramount to differentiate benign lesions from malignancies, since their treatment strategies and prognoses drastically differ (1). Approaches to the lesions can even vary among different benign masses. Simple or follicular cysts do not require surgery at all, whereas epithelial tumors need to be resected for pathologic confirmation of their benignity and relief of the symptoms caused by mass effects. The treatment plan for endometriotic cysts varies based on the extent and severity of symptoms.Ultrasonography (US) is often the first imaging method performed in the evaluation of an ovarian lesion because it is widely available, well accepted by the patients, noninvasive and inexpensive (2). Magnetic resonance imaging (MRI) is an essential problem solving tool for characterizing an US-indeterminate adnexal mass, owing to its high resolution with excellent soft tissue contrast, possessing proven superiority over other modalities (1–4). Computed tomography (CT) is generally not intended for primary pelvic or gynecologic evaluation in women, unlike US or MRI (5). Its value in tumor characterization is limited by the detection of fat or calcifications within the lesion and the assessment of its rough shape, which may, but not necessarily, lead to a specific diagnosis (2, 3). In contrast to its suboptimal diagnostic value, recent widespread use of CT has commonly resulted in the incidental initial detection of an adnexal lesion (4–7).Common benign adnexal cystic lesions include functional cysts, serous cystadenomas, mucinous cystadenomas, and endometriotic cysts. Mucinous cystadenomas are characterized as multilocular cystic adnexal masses with variable internal mucinous contents and relatively large size at the time of presentation (2, 3, 8). As with most ovarian masses, it is challenging to make a specific diagnosis of mucinous cystadenoma and exclude other pathologic types, particularly when either US or CT is the only available modality. Two prior studies reported that the detection rates for mucinous cystadenoma using US, CT, and MRI were 50%, 62%, and 70%, respectively (9, 10). On MRI, mucinous tumors classically have a “stained glass appearance” with variable intralocular signal intensities, which allows a more specific differential diagnosis from other tumors than is possible with US and CT (2, 11). However, MRI is too costly and time-consuming to be performed routinely for incidentally found benign diseases.Recent advances in endoscopic surgical techniques have offered new possibilities for the laparoscopic treatment of large ovarian cysts, including mucinous cystadenomas, rather than laparotomy (12). The fluid content of a large cyst must be aspirated before it can be laparoscopically excised and removed (12). However, thick internal materials such as mucin or fat may impair this procedure. One reported case of laparoscopy had to be converted to open laparotomy due to an inability to aspirate the cyst’s liquid contents (13). The laparoscopic removal of large mucinous cystadenomas also poses the risk of spillage, which can cause pseudomyxoma peritonei (14–16). Therefore, it would be helpful to properly analyze the cyst’s internal contents and correctly preoperatively characterize the nature of the lesion to plan the surgery and avoid complications. Because of the limited availability of MRI, we evaluated the utility of CT with added texture analysis to differentiate the internal mucinous contents of ovarian cysts from serous fluid and eventually predict the pathologic diagnosis of the adnexal cystic lesion. Texture analysis is a method used to quantitatively evaluate pixel densities in medical images. Although texture analysis had been used in some previous studies on ovarian cancers, no study has performed texture analysis in ovarian cysts (17–19).Consequently, the purpose of this study is to evaluate the benefit of adding CT texture analysis to conventional CT features when diagnosing benign adnexal cystic lesions, and especially when identifying mucinous cystadenoma.     

Fibroadenoma versus phyllodes tumor: distinguishing factors in patients diagnosed with fibroepithelial lesions after a core needle biopsy

PURPOSE

We aimed to identify factors that might help differentiate phyllodes tumors from fibroadenomas among cases in which a fibroepithelial breast lesion was diagnosed from core needle biopsy (CNB) under imaging guidance.

MATERIALS AND METHODS

A retrospective review was performed on 213 lesions in 200 patients who had undergone both CNB and excisional biopsy during a four-year period between 2008 and 2011. The final pathology revealed 173 fibroadenomas and 40 phyllodes tumors. The data, including patient characteristics, clinical presentation, and mammography, ultrasonography (US), and pathology findings were analyzed.

RESULTS

Upon univariable analysis, the factors that significantly helped to identify phyllodes tumors consisted of the presenting symptoms (palpable mass or breast pain), increased size on clinical examination, hyperdense mass on mammogram, and the following three US features: heterogeneous echo, presence of round cysts within the mass, and presence of clefts within the mass. The pathologist’s suggestion of a phyllodes tumor was also helpful. The factors that remained statistically significant upon multivariable analysis consisted of symptoms of breast pain, the presence of clefts on US, the presence of round cysts on US and the pathologist’s favoring of phyllodes tumors from a CNB specimen.

CONCLUSION

A multidisciplinary approach was needed to distinguish phyllodes tumors from fibroadenomas in patients who had undergone CNB. US findings (clefts and round cysts), suggestive pathological diagnoses, and clinical symptoms were all useful for the decision to surgically remove the fibroepithelial lesions diagnosed from CNB.Core needle biopsy (CNB) under imaging guidance is an accepted standard of care for the diagnosis of breast lesions, particularly those that are nonpalpable (1–4). This procedure is safe, cost-effective and minimally invasive compared with surgical excision (1).In general, CNB allows for appropriate decision-making. Surgery could be obviated by a benign CNB pathology result. At times, however, CNB may provide only an inconclusive histopathology or may yield results associated with a potentially more worrisome pathology. Surgical excision may be needed in such circumstances.Fibroadenoma is the most common lesion in the breast, occurring in 25% of asymptomatic women (5), and it is usually readily diagnosed via CNB. In the presence of increased stromal cellularity, however, it is less likely to be distinguishable from a phyllodes tumor (1–4). In such cases, the term “fibroepithelial lesion” is used (1–5).The distinction between fibroadenomas and phyllodes tumors is clinically important. Fibroadenomas may be safely followed without further investigation. Even if an excisional biopsy is needed, the simple enucleation of a fibroadenoma is appropriate (1). In contrast, phyllodes tumors should not be managed by nonoperative means because they commonly and progressively enlarge. Moreover, wide excision of phyllodes tumors with adequate margins is essential to the prevention of local recurrence and to provide an accurate diagnosis as to whether it is benign, borderline or malignant (1–5). A CNB-diagnosed fibroepithelial lesion, therefore, provides the surgeon with the dilemma of whether to operate. Usually, surgical excision is chosen, and a considerable amount of normal breast tissue is sacrificed.The purpose of the present study was to determine factors that might help differentiate phyllodes tumors from fibroadenomas among cases in which a fibroepithelial lesion was diagnosed from CNB under imaging guidance.     

Adrenal venous sampling for stratifying patients for surgery of adrenal nodules detected using dynamic contrast enhanced CT

PURPOSE

We aimed to assess the value of adrenal venous sampling (AVS) for diagnosing primary aldosteronism (PA) subtypes in patients with a unilateral nodule detected on adrenal computed tomography (CT) and scheduled for adrenalectomy.

MATERIALS AND METHODS

This retrospective study included 80 consecutive patients with PA undergoing CT and AVS. Different lateralization indices were assessed, and a cutoff established using receiver operating characteristic curve analysis. The value of CT alone versus CT with AVS for differentiating PA subtypes was compared. The adrenalectomy outcome was assessed, and predictors of cure were determined using univariate analysis.

RESULTS

AVS was successful in 68 patients. A cortisol-corrected aldosterone affected-to-unaffected ratio cutoff of 2.0 and affected-to-inferior vena cava ratio cutoff of 1.4 were the best lateralization indices, with accuracies of 82.5% and 80.4%, respectively. CT and AVS diagnosed 38 patients with aldosterone-producing adenomas, five patients with unilateral adrenal hyperplasia, and 25 patients with bilateral adrenal hyperplasia. Of the 52 patients with a nodule detected on CT, subsequent AVS diagnosed bilateral adrenal hyperplasia in 14 patients (27%). Compared to the results of combining CT with AVS, the accuracy of CT alone for diagnosing aldosterone-producing adenomas was 71.1% (P < 0.001). The cure rate for hypertension after adrenalectomy was 39.2%, with improvement in 53.5% of patients. On univariate analysis, predictors of persistent hypertension were male gender and preoperative systolic blood pressure.

CONCLUSION

To avoid inappropriate surgery, AVS is necessary for diagnosing unilateral nodules with aldosterone hypersecretion detected by CT.Primary aldosteronism (PA) is the most common form of secondary hypertension, with a prevalence of 5%–11% (1–3). PA is due primarily to the hypersecretion of aldosterone by an aldosterone-producing adenoma (APA) or unilateral (primary) adrenal hyperplasia (UAH), which constitute 30%–40% of cases; the remainder are presumed to be secondary to idiopathic bilateral adrenal hyperplasia (BAH) (1, 4, 5). APA and UAH are two forms of unilateral aldosterone hypersecretion, and both are curable with adrenalectomy. BAH induces bilateral aldosterone hypersecretion, and anti-aldosterone drugs are used in its medical management (5–7).The plasma aldosterone-to-renin ratio is used to screen for PA in patients at high risk for PA (8). Recent guidelines recommend using computed tomography (CT) of the adrenal gland to categorize the subtype after confirming PA. However, CT cannot reliably visualize a microadenoma or distinguish between an incidentaloma or BAH and APA. It has been suggested that adrenal venous sampling (AVS) be performed to determine the subtype of PA and to differentiate between unilateral and bilateral production of aldosterone preoperatively (9). AVS to measure the adrenal vein aldosterone and cortisol is the gold standard for lateralizing aldosterone secretion (10). Lateralization is defined using several ratios. In patients with APA or UAH, a unilateral adrenalectomy results in a complete cure or improved hypertension and potassium normalization in approximately 30% of patients, with reported rates up to 86% (11–15).This study assessed several lateralization ratios to establish the most predictive of unilateral disease. We also compared the CT results with those of bilateral AVS for differentiating the PA subtype, with the assumption that AVS is necessary before surgery, even in patients with nodules <10 mm detected with CT. Finally, we assessed the outcomes of adrenalectomy in our patients to identify preoperative predictors of a good outcome.     

Diagnostic performance rates of the ACR-TIRADS and EU-TIRADS based on histopathological evidence

PURPOSEIn this study, we aimed to assess the effectiveness of malignancy stratification algorithms of the American College of Radiology (ACR) and European Thyroid Association (ETA) in the delineation of thyroid nodules using a database of nodules that were unequivocally diagnosed by means of histopathological examination and meticulously matched with the imaged nodules.METHODSA total of 165 patients having 251 thyroid nodules with histopathologically proven definitive diagnoses during a 5-year period were included in this study. All patients had preoperatively undergone ultrasonography (US) examination, and US characteristics of the thyroid nodules were retrospectively analyzed and assigned in compliance with the thyroid imaging reporting and data system categories recommended by the ACR (ACR-TIRADS) and ETA (EU-TIRADS). The diagnostic effectiveness in the delineation of thyroid nodules and unnecessary fine-needle aspiration (FNAB) rates were evaluated.RESULTSOverall, 189 nodules (75.30%) were diagnosed as benign, while 62 nodules (24.70%) were reported to be malignant based on histopathological assessment. Sensitivity and specificity rates were 71% and 75% for ACR-TIRADS and 73% and 80% for EU-TIRADS. The area under the curve values were 0.78 and 0.80 for ACR-TIRADS and EU-TIRADS, respectively. The unnecessary FNAB rates were 61% for ACR-TIRADS and 64% for EU-TIRADS as per the recommended criteria of each algorithm.CONCLUSIONThe diagnostic performance of both malignancy stratification systems was signified to be moderate and sufficient in a cohort of nodules with definite histopathological diagnosis. In light of our results, we demonstrated the strengths and weaknesses of the ACR- and EU-TIRADS for physicians who should be familiar with them for optimal management of thyroid nodules.

The number of detected thyroid nodules has been increasing in recent years with the widespread application of ultrasonography (US). The reported incidence varies from 20% to 68% in patients undergoing high-frequency US examination (1, 2). In case of a newly detected nodule, the primary concern is to discriminate benign ones, which constitute almost 90%, from malignant ones that require additional invasive procedures (3, 4). Fine-needle aspiration biopsy (FNAB) is the primary diagnostic tool due to its high sensitivity and specificity in distinguishing malignancy, yet it has several shortcomings, including inconclusive results and potential overdiagnosis (5).The particular nodular US features suggestive of malignancy are well known and thus US is employed for the indication of FNAB (6, 7). Nevertheless, none of those characteristics individually predicts the malignancy risk sufficiently (8, 9). Hence, various risk-stratification systems that consider a set of nodular US features have been established to predict the malignancy risk, mitigate superfluous FNABs, and enhance interobserver concordance. Among them, the Thyroid Imaging Reporting and Data System of the American College of Radiology (ACR-TIRADS) was set up in 2017 to classify all detected thyroid nodules according to its issued lexicon (10–12). Similarly, the European Thyroid Association TIRADS (EU-TIRADS) was developed to improve the sensitivity together with high negative predictive value (NPV) in characterization with a more straightforward scoring method (12, 13). Several studies have compared the effectiveness of these two risk-stratification systems (14–18), yet their performance in different thyroid nodules with various histopathologic results and subtypes still needs to be investigated.The objectives of our study were to appraise the diagnostic effectiveness of the ACR- and EU-TIRADS classification systems in nodular characterization and to analyze the rates of inappropriate FNABs according to the proposed criteria based on unequivocal histopathological results.     

Role of magnetic resonance spectroscopy in differential diagnosis of solitary pulmonary lesions

PURPOSEThe aim of our study was to evaluate the availability of magnetic resonance spectroscopy (MRS) for the differentiation of benign or malignant pulmonary nodules and masses.METHODSA total of 59 patients (45 male, 14 female) with pulmonary nodules and masses were included in this prospective study. MRS was applied to the pulmonary lesions of the patients and choline levels were determined. Afterwards CT-guided percutaneous needle biopsy was performed. According to the biopsy results, pulmonary lesions were benign in 25 patients and malignant in 34 patients.RESULTSCholine levels were significantly higher in malignant lesions compared with benign lesions (p < 0.001). When the other conditions were kept constant, the probability of malignancy significantly increased by 17.38-fold (95% CI, 3.78–79.93) in those with choline levels >1.65 μmol/g compared to those with choline levels ≤1.65 μmol/g (p < 0.001).CONCLUSIONMRS is a noninvasive method that can be used in the differential diagnosis of pulmonary nodules and masses.

The majority of the solitary pulmonary nodules have a benign character (1). However, all pulmonary nodules should be considered as malignant lesions unless proven otherwise (2). The differential diagnosis of these lesions may be an important problem in routine medical practice. Computed tomography (CT) is the standard method for the examination of the nodules and mass lesions (3). CT imaging of morphological features like size, margins, and calcification enables the investigation of malignancy (4). However, there is some overlap so that some malignant lesions may appear benign, while some benign nodules may show morphological features typical for malignancy (5). CT imaging for differantial diagnosis have problems like false-negative and false-positive results, over-diagnosis, benign nodule resections, and exposure to radiation (6). Biopsy is the most reliable and effective method for the diagnosis of the pulmonary nodules and mass lesions. However, it may cause serious complications such as pneumothorax, hemoptysis, air embolism, tumor cell seeding and death (7, 8). In addition, the tolerability of this invasive intervention is rather low among patients.Magnetic resonance imaging (MRI) provides information about the tumor morphology and magnetic resonance spectroscopy (MRS) provides biochemical information about the physiology and metabolism of the disease (9). MRS enables molecular analysis of the tissues based on the display of different chemical shifts of certain nuclei in the magnetic field (10). MRS was initially used in neuroradiology for characterization of tumor, stroke, epilepsy, infection, and neurodegenerative diseases. In recent years, it was also introduced in the evaluation of lesions in other organs like breast (11), liver (12), pancreas (13), and prostate (14). There are some in vitro studies in the literature on the use of MRS in lung cancer showing higher lactate and total choline peaks compared with normal tissues (15, 16). Also there is one case report in the literature regarding the feasibility of using MRS in lung cancer (17).The objective of this study was to demonstrate the value of MRS, which is a noninvasive method and does not require a contrast agent, in the differential diagnosis of pulmonary nodules and mass lesions.     

Use of full-dose contrast-enhanced CT for extrahepatic staging using Gallium-68-DOTATATE PET/CT in patients with neuroendocrine tumors

PURPOSEStudies have demonstrated that positron emission tomography/computed tomography (PET/CT) with Gallium-68 (⁶⁸Ga)-labeled somatostatin analogues are effective at detecting metastatic disease in neuroendocrine tumors (NET), especially extrahepatic metastases. However, PET in combination with full-dose contrast-enhanced CT (ceCT) exposes patients to higher radiation (~25 mSv). The use of non-contrast-enhanced low-dose CT (ldCT) can reduce radiation to about 10 mSv and may avoid contrast-induced side effects. This study seeks to determine whether ceCT could be omitted from NET assessments.METHODSWe retrospectively compared the performance of PET/ldCT versus PET/ceCT in 54 patients (26 male, 28 female) who had undergone a ⁶⁸Ga-DOTATATE PET/CT. The selection criteria were as follows: available ldCT and ceCT, histologically confirmed NET, and follow-up of at least 6 months (median, 12.6 months; range, 6.1–23.2 months). The PET/ldCT and PET/ceCT images were analyzed separately. We reviewed metastases in the lungs, bones, and lymph nodes. The results were compared with the reference standard (clinical follow-up data).RESULTSThe PET/ceCT scans detected 139 true-positive bone lesions compared with 140 lesions detected by the PET/ldCT scans, 106 true-positive lymph node metastases (PET/ceCT) compared with 90 metastases detected by the PET/ldCT scans, and 26 true-positive lung lesions (PET/ceCT) compared with 6 lesions detected by the PET/ldCT scans. The overall lesion-based sensitivity for full-dose PET/ceCT was 97%, specificity 86%, negative predictive value (NPV) 93%, and positive predictive value (PPV) 93%. The overall lesion-based sensitivity for PET/ldCT was 85%, specificity 73%, NPV 72%, and PPV 85%.CONCLUSIONThis study presents the first evidence that ceCT should not be omitted from extrahepatic staging using ⁶⁸Ga-DOTATATE PET/CT in patients with NET. ceCT alone can be used as a follow-up to reduce radiation exposure when the patient has already undergone PET/ceCT and suffers from non-DOTATATE-avid NET.

Previous studies have shown the importance of DOTATOC, DOTATATE, and DOTANOC PET/CT imaging in the diagnosis and accurate staging of neuroendocrine tumors (NET) (1–3). The use of radiolabeled somatostatin analogs in PET/CT has become the standard protocol in NET staging. For many years, octreotide-scintigraphy was used for NET detection and assessment, but this practice has recently been replaced by combined, integrated PET/CT imaging with ⁶⁸Ga-labelled somatostatin analogues. The new method yields higher spatial resolution and facilitates tracer uptake quantification, and ⁶⁸Ga PET/CT has increasingly replaced the use of contrast-enhanced computed tomography (ceCT) alone. ⁶⁸Ga PET/CT provides for precise staging and allows the physician to assess the feasibility of peptide receptor radionuclide therapy (4, 5). There is evidence that PET/ceCT can be beneficial for patients with NET and the ENETS guidelines, among others, recommend PET/ceCT for staging NETs (6–8). However, to date, there is no mandatory consensus on the appropriate ⁶⁸Ga PET/CT protocol for assessing NET. A patient can undergo PET with non-contrast-enhanced low-dose CT (ldCT) or with full-dose ceCT. The diagnostic benefit of surplus ceCT has been assessed particularly for the detection and staging of ¹⁸F-fluorodeoxyglucose (FDG)- avid lymphoma (5) and NET abdominal lesions (9). The benefits of ceCT over PET/ldCT in the detection of extrahepatic metastases have not been analyzed with that kind of detail. As the ceCT method results in substantial radiation exposure (up to 25 mSv), depending on the type of CT machine, any potential dose reduction is desirable. While these levels of exposure are within the limits recommended by Huang et al. (10), they surpass those given by Persson et al. (11). In addition, contrast medium can cause adverse reactions such as hyperthyroidism and renal failure, so it should not be administered without cause, although current ESUR guidelines suggest that contrast media’s adverse effects have been widely overestimated (12). This study addresses whether ceCT is necessary for the detection and assessment of NET extrahepatic metastases and if PET/ldCT is sufficiently reliable.     

Establishment of a large animal model for research on transbronchial arterial intervention for lung cancer

PURPOSEWe aimed to evaluate whether bronchial artery can supply a percutaneously inoculated canine transmissible venereal tumor (CTVT) in a lung tumor model.METHODSFresh CTVT tissue blocks were percutaneously inoculated into unilateral or bilateral lungs of six immunosuppressed dogs at the mid zone of the middle or lower lobe. Tumor growth was monitored by computed tomography (CT). Ten weeks after inoculation, pulmonary arterial digital subtraction angiography (DSA), bronchial arterial DSA, transpulmonary arterial contrast-enhanced multislice CT, transbronchial arterial contrast-enhanced multislice CT (BA-MSCT), and transpulmonary arterial lipiodol multislice CT were performed.RESULTSTumor growth was seen in all 10 inoculated sites, with a maximum diameter of 2.734±0.138 cm at 10th week. Bronchial arterial blood supply was evident in 9 nodules on DSA, and was equivocal in one which was later demonstrated on BA-MSCT. No obvious pulmonary arterial blood supply was observed in any of the nodules. Lipiodol deposition was displayed in two of the small distant metastases, which indicated that pulmonary artery was involved in the supply of the metastases.CONCLUSIONOur results demonstrated bronchial arterial blood supply in this new lung cancer model. This model may be used in further research on transbronchial arterial intervention for lung cancer.

Bronchial arterial infusion chemotherapy (BAI) for lung cancer was introduced into clinical practice 50 years ago (1–3). Theoretically, better reductions in tumor size and symptoms, and less adverse effects of anticancer drugs could be achieved with direct infusion of high-density chemotherapeutics into tumors. However, BAI for lung cancer is not widely accepted. In the last two decades, only a few small case series were published in the English literature showing favorable results (4–9). This may be explained by several reasons: the outcomes have not been confirmed, severe complications have been reported (10, 11), the pharmacokinetics of BAI has not been fully understood, the indications and the treatment protocols have not been defined (4, 12). In the near future, the role of BAI or other transbronchial arterial therapy in the combined treatment of lung cancer may be reappraised, given the poor 5-year survival rate of less than 17% despite improvements in therapeutic management (13).Unfortunately, there is currently no large animal lung cancer model for fundamental research on transbronchial arterial therapy. In 2002, Ahrar et al. (14) developed a canine lung tumor model by intra-arterial or percutaneous inoculation of canine transmissible venereal tumor (CTVT) fragments, which was later used for study on percutaneous radiofrequency ablation (15). It is well known that metastatic lung cancer receives blood supply from both pulmonary artery and bronchial artery, with peripheral tumors having a predominant pulmonary circulation and central tumors having a predominant bronchial circulation (16). Our study goal is to evaluate the blood supply of this large animal lung tumor model.     

Imaging of facial nerve schwannomas: diagnostic pearls and potential pitfalls

Schwannomas are uncommon in the facial nerve and account for less than 1% of tumors of temporal bone. They can involve one or more than one segment of the facial nerve. The clinical presentations and the imaging appearances of facial nerve schwannomas are influenced by the topographical anatomy of the facial nerve and vary according to the segment(s) they involve. This pictorial essay illustrates the imaging features of facial nerve schwannomas according to their various anatomical locations and also reviews the pertinent differential diagnoses and potential diagnostic pitfalls.Facial nerve schwannomas (FNSs) are rare slow-growing tumors, accounting for less than 1% of all temporal bone tumors. They are typically solitary, unilateral, and sporadic in nature. FNSs may be bilateral as part of neurofibromatosis-2 spectrum (1, 2). Rarely, multiple schwannomas may involve peripheral branches of the facial nerve (FN) (3). The age of presentation varies from 5 to 84 years. No gender or side predilection is seen (4, 5).Histologically, FNSs are neuroectodermal in origin. They are encapsulated, benign tumors arising from the Schwann cells. They may show intratumoral cystic change and hemorrhage (3, 4, 5). Malignant schwannoma of the FN is extremely rare (6). FNSs commonly present with peripheral facial neuropathy and/or various otologic symptoms including sensorineural and conducting hearing loss (2–5). Facial paralysis is often seen at a later stage or may not be seen at all. The reasons for this are thought to be neuronal tolerance induced by the extremely slow growth of the tumor, abundant tumor vascularity, and commonly associated dehiscence of adjacent bone (7). Occasionally, FNSs may present as an intraparotid mass or as an intracranial lesion (2–5).The clinical presentations and the imaging appearances of FNSs are influenced by the topographical imaging anatomy of the FN and vary according to the segment(s) they involve (8). Here, we briefly describe the anatomy of the FN, followed by general imaging features of FNSs on computed tomography (CT) and magnetic resonance imaging (MRI), and appropriate imaging protocols. Tumor involving each segment is reviewed in relation to its characteristic clinical presentations emphasizing diagnostic pearls and potential pitfalls. The imaging examples of FNSs illustrated in this pictorial review are all histopathologically proven cases.     

Assessment of complication rates based on time of feeding initiation in radiologically guided gastrostomy tubes: a retrospective study

PURPOSEWe aimed to assess the association between complication rate and time to feeding in a cohort of patients undergoing radiologically guided placement of gastrostomy tubes.METHODSA retrospective study was conducted of all patients receiving pull-type and push-type gastrostomy tubes placed by interventional radiologists between January 1^st, 2017 and December 31^st, 2018 at a single institution. Primary outcomes included procedural and tube-related complications per medical chart review with a follow-up interval of 30 days. Exclusion criteria were enteral nutrition delayed more than 48 hours, no feeding information, and tubes placed for venting (n=20). Overall, 303 gastrostomy tubes (pull-type, n=184; push-type, n=119) were included. The most common indications for placement included head and neck carcinoma for push-type tubes (n=76, 63.9%) and cerebral vascular accident for pull-type tubes (n=78, 42.4%).RESULTSIn a multiple regression analysis, there was no statistically significant association between complications and time to feeding (p = 0.096), age (p = 0.758), gender (p = 0.127), indication for tube placement (p = 0.206), or type of tube placed (p = 0.437). Average time to initiation of enteral nutrition was 12.3 hours for the pull-type and 21.7 hours for the push-type cohort (p < 0.001). Additional multiple regression analyses of pull-type tubes and push-type tubes separately also did not find any significant association between complications and the above factors (p > 0.05).CONCLUSIONThere was no statistically significant correlation between time to feed and complications, suggesting that there is no clinical difference between early and late feeding following gastrostomy tube placement.

Percutaneous radiologic gastrostomy is a well-established safe and effective feeding method (1–5). Early initiation of feeding after tube placement has several benefits, including decreased hospital stay and shorter time on intravenous nutrition, but the theoretical risk of increased complication rate has led many physicians to delay feeding initiation. While several studies have found that early initiation of feeding after tube placement is safe in the endoscopic literature (6–10), the association between time to feed and complications has been less frequently studied in the radiologic literature. Studies that have done so have been limited in the methods of tube placement included, sample size, and types of patients included (11, 12). Furthermore, despite evidence in the endoscopic literature, many physicians do not initiate early feeding after either endoscopic or radiologic gastrostomy placement (13).Within interventional radiology, the time to initiation of enteric feeding is one variable that remains discrepant between institutions and may pose consequence with respect to complications in the early post-placement setting (6–9, 11, 14, 15). Fora of interventional radiologists have demonstrated physicians are using a wide variety of fasting times following tube placement ranging from “early” (commonly less than 6 hours) to “delayed” (commonly 24 hours or greater) that is neither directly based on evidence nor guideline based (16). Furthermore, time to feeding following gastrostomy remains an important clinical metric that may impact initiation of therapy, feeding, and hospital discharge. The purpose of this study was to analyze the rate of feeding related complications in a cohort of all patients undergoing either “push” or “pull” type radiologic gastrostomy placement at a single institution based on time to initiation of feeding following tube placement.     

Spin-echo and diffusion-weighted MRI in differentiation between progressive massive fibrosis and lung cancer

PURPOSEWe aimed to investigate the value of magnetic resonance imaging (MRI)-based parameters in differentiating between progressive massive fibrosis (PMF) and lung cancer.METHODSThis retrospective study included 60 male patients (mean age, 67.0±9.0 years) with a history of more than 10 years working in underground coal mines who underwent 1.5 T MRI of thorax due to a lung nodule/mass suspicious for lung cancer on computed tomography. Thirty patients had PMF, and the remaining ones had lung cancer diagnosed histopathologically. The sequences were as follows: coronal single-shot turbo spin echo (SSH-TSE), axial T1- and T2-weighted spin-echo (SE), balanced turbo field echo, T1-weighted high-resolution isotropic volume excitation, free-breathing and respiratory triggered diffusion-weighted imaging (DWI). The patients’ demographics, lesion sizes, and MRI-derived parameters were compared between the patients with PMF and lung cancer.RESULTSApparent diffusion coefficient (ADC) values of DWI and respiratory triggered DWI, signal intensities on T1-weighted SE, T2-weighted SE, and SSH-TSE imaging were found to be significantly different between the groups (p < 0.001, for all comparisons). Median ADC values of free-breathing DWI in patients with PMF and cancer were 1.25 (0.93–2.60) and 0.76 (0.53–1.00) (× 10⁻³ mm²/s), respectively. Most PMF lesions were predominantly iso- or hypointense on T1-weighted SE, T2-weighted SE, and SSH-TSE, while most malignant ones predominantly showed high signal intensity on these sequences.CONCLUSIONMRI study including SE imaging, specially T1-weighted SE imaging and ADC values of DWI can help to distinguish PMF from lung cancer.

Pneumoconiosis, defined as the accumulation of inhaled particles is relatively common in industrial areas (1). Coal worker’s pneumoconiosis, silicosis, and asbestosis are the most common forms of pneumoconiosis (2). Progressive massive fibrosis (PMF) of the lung is defined as a combination of anthracosilicotic nodules and connective tissue, and it may be seen in the chronic stage of pneumoconiosis (1).The imaging features of PMF on chest radiography and computed tomography (CT) have been well investigated (3, 4). The main characteristic finding of PMF on CT is an irregular nodule or mass with or without calcification, located mostly in the upper and middle lung zones (5). However, it is occasionally difficult to distinguish PMF from lung cancer due to a similar appearance on these imaging modalities as well as similar clinical presentation. The differentiation is especially difficult, when PMF lesion appears as a mass or mass-like lesion and grows in size during the follow-up. Additionally, lung cancer may be seen together with underlying PMF lesion. 18F-fluoro-2-deoxy-D-glucose positron emission tomography/CT (¹⁸F-FDG PET/CT) can be used in differentiation between PMF and lung cancer but it may not be helpful in some cases (6).Magnetic resonance imaging (MRI) with high conrast resolution and additional diignostic facility tools may be helpful in terms of avoiding biopsy and its possible complications in the differentiation between PMF and lung cancer (7, 8). A low signal intensity (SI) on T2-weighted MRI and a gradual increase in SI in a dynamic MRI study are the reported, characteristic MRI findings of PMF (9, 10). However, the use of several MRI sequences has not yet been fully explored for the differentiation between PMF and lung cancer. In addition to the SI changes, assessment of quantitative MRI parameters could also be helpful in the differentiation of these entities. The purpose of this study was to investigate the value of MRI-based parameters in differentiating between PMF and lung cancer.     

The reliability and interobserver reproducibility of T2/FLAIR mismatch in the diagnosis of IDH-mutant astrocytomas

PURPOSEThe reliability and reproducibility of T2-weighted imaging/fluid-attenuated inversion recovery (T2/FLAIR) mismatch were investigated in the diagnosis of isocitrate dehydrogenase (IDH) mutant astrocytoma between WHO grade II and III diffuse hemispheric gliomas.METHODSWHO grade II and grade III diffuse hemispheric gliomas (n=133) treated in our institute were included in the study. Pathological findings and molecular markers of the cases were reviewed with the criteria of WHO 2016. The finding of mismatch between T2-weighted and FLAIR images in preoperative magnetic resonance imaging (MRI) of the cases was evaluated by two different radiologists. The readers reviewed MRIs independently, blinded to the histopathologic diagnosis or molecular subset of tumors. The cases were classified as IDH-mutant astrocytoma, oligodendroglioma and IDH-wildtype (IDH-wt) astrocytoma according to molecular and genetic features.RESULTST2/FLAIR mismatch positivity was observed in 46 patients (34.6%). T2/FLAIR mismatch positivity was observed in 42 of 75 IDH-mutant astrocytomas (56%) and 4 of 43 oligodendrogliomas (9.30%), while it was not seen among IDH-wt astrocytomas (0/15, 0%). The T2/FLAIR mismatch ratio was significantly different between IDH-mutant astrocytomas (WHO grade II and grade III) and oligodendrogliomas (chi-square, p <0.05). The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of T2/FLAIR mismatch in predicting IDH-mutant astrocytomas were 58.7%, 90.7%, 91.7%, 61.4%, and 70.3% respectively. Radiologist 1 diagnosed T2/FLAIR mismatch in 48 of 133 cases (36.1%) and Radiologist 2 in 66 of 133 cases (49.6%). The interrater agreement for the T2/FLAIR mismatch sign was 0.61 (p <0.05), 95% CI (0.55, 0.67).CONCLUSIONT2/FLAIR mismatch appears to be an important MRI finding in distinguishing IDH-mutant astrocytomas from other diffuse hemispheric gliomas. However, it should be kept in mind that T2/FLAIR mismatch sign can be seen in a minority of oligodendrogliomas besides IDH-mutant astrocytomas.

Preoperative prediction of histopathological diagnosis of tumors is highly relevant during treatment of diffuse hemispheric gliomas (DHG). This preliminary diagnosis strongly influences the treatment plan and the surgical strategy. Isocitrate dehydrogenase (IDH) mutant gliomas constitute the majority of DHG (WHO grade II and grade III) (1, 2). Among IDH-mutant gliomas there are two tumor entities: IDH-mutant astrocytoma and IDH-mutant 1p/19q co-deleted oligodendroglioma (3). A smaller proportion of DHG carry molecular alterations of glioblastoma and such tumors exhibit a tumor biology comparable to glioblastomas (1, 2, 4). Independent of the WHO grade, DHG with no IDH mutation exhibit worse prognosis than their IDH-mutant counterparts (5). Each of these three molecular tumor subsets has a very different tumor biology and requires a matching treatment strategy, which underlines the importance of noninvasive preoperative diagnosis.Conventional magnetic resonance imaging (MRI) and computed tomography (CT) imaging is widely used to differentiate these tumors. Coarse calcifications, which are best visible on unenhanced CT scans are characteristic to oligodendrogliomas and absent in astrocytomas. Other typical features of oligodendrogliomas are a cortical-subcortical location and a more heterogeneous appearance of astrocytomas on T2-weighted images (6). Advanced MRI sequences also have a potential to noninvasively identify these DHGs. In perfusion-weighted imaging, higher cerebral perfusion volumes are observed in oligodendrogliomas compared to astrocytomas (7).In 2017, Patel et al. (8) presented an analysis of The Cancer Genome Atlas (TCGA) cohort and showed that in lower-grade gliomas, the T2/FLAIR mismatch sign represented a highly specific imaging biomarker for the IDH-mutant, 1p/19q non co-deleted molecular subtype. The T2/FLAIR mismatch denotes that the tumor has a high and homogeneous signal intensity on T2-weighted images whereas it has relatively hypointense signal with a hyperintense rim on T2-FLAIR images. Jain et al. (9) have shown that it may have false positives due to interobserver variability in application of the signs imaging criteria, differences in image acquisition and selection of the applied cohort. Therefore we sought to determine the reliability and reproducibility of the T2/FLAIR mismatch in the diagnosis of IDH-mutant astrocytoma among WHO grade II and III diffuse gliomas in our own institutional cohort, which is of comparable size to the original study by Patel et al. (8).     

Monitoring the therapeutic efficacy of CA4P in the rabbit VX2 liver tumor using dynamic contrast-enhanced MRI

PURPOSEThe present work aims to evaluate whether dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) can monitor the blocking effect of combretastatin-A4-phosphate (CA4P) on microvessels and assess the therapeutic efficacy.METHODSForty rabbits were implanted VX2 tumor specimens. Two weeks later, serial MRI (T1-weighted imaging, T2-weighted imaging, and DCE) were performed at 0 h, 4 h, 24 h, 3 days, and 7 days after CA4P (10 mg/kg) or saline treatment. The parameters of DCE (K^trans, K_ep, V_e and iAUC60) enhancement of tumor portions were measured. Then all tumor samples were stained to count microvessel density (MVD). Finally, two-way repeated measures ANOVA was used to analyze the difference between and within groups. Correlation between the DCE parameters and MVD was analyzed by using the Pearson correlation and Spearman rank correlation.RESULTSK^trans and iAUC60 values at 4 h after CA4P treatment were significantly lower than those in the control group (D-value: −0.133 min⁻¹, 95%CI: −0.169 to −0.097 min⁻¹, F= 59.109, p < 0.001 for K^trans; D-value: −10.533 mmol/s, 95%CI: −17.147 to −3.919 mmol/s, F= 11.110, and p = 0.003 for iAUC60). In the CA4P group, K^trans and iAUC60 reached the minimum values at 4 h, and both parameters showed significant difference between 4 h and other time points (all p < 0.01). Seven-day values of K^trans (r=0.532, p = 0.016 and r=0.681, p = 0.001, respectively) and iAUC60 (r=0.580, p = 0.007 and r=0.568, p = 0.009, respectively) showed correlation with MVD in both groups, while K_ep and V_e did not show correlation with MVD (p > 0.05).CONCLUSIONThe blocking effect of microvessels after CA4P treatment can be evaluated by DCE-MRI, and the parameters of quantitative K^trans and semi-quantitative iAUC60 can assess the change in tumor angiogenesis noninvasively.

Hepatocellular carcinoma (HCC) has the third highest mortality rate worldwide among cancers (1). Although the 5-year survival rate can reach up to 70% of HCC patients by surgical operation, only less than 30% are suitable for surgery. Transarterial chemoembolization (TACE) treated tumors can stimulate angiogenesis and require repeated treatment (2). As HCC is generally hypervascular, vascular targeting strategies can be used to improve the 5-year survival rate (3).There are two kinds of tumor vascular targeted agents (4): angiogenesis inhibitors (AIs) and vascular disrupting agents (VDAs). AIs can prevent the formation of new blood vessels by inhibiting angiogenesis. VDAs can damage the tumor endothelium directly, shutdown vascular development rapidly and selectively and cause tumor cell ischemia; tumor vascular shutdown occurs within 1 h of administration, and lasts for 24 hours (5, 6). Combretastatin A-4-phosphate (CA4P) is a new-style VDA that progressed into clinical trial stage (7–9).The vascular disrupting effects of VDAs can be assessed by microvessel density (MVD), which is the “gold standard” measurement to evaluate angiogenesis. However, the invasiveness of MVD measurement limits its use (10).During the development of targeted treatments, imaging plays an important role in monitoring the treatment efficacy against malignant tumors (11). Although change in tumor size may not be a reliable method to measure treatment efficacy, plenty of imaging sequences have been developed to overcome the drawbacks of traditional efficacy assessments by size measurement (12–14).DCE-MRI could reflect the microvascular structure and function indirectly, noninvasively and quantitatively, and it has been widely applied to predict and evaluate the treatment response (15). DCE-MRI is expected to be useful in evaluating early vascular disrupting efficacy after CA4P administration. But studies focusing on the changes of DCE parameters at different time points after CA4P administration in the VX2 rabbits have been scarce (16–18). The VX2 liver tumor is supplied by liver artery which is similar with high-grade human HCC, and can be used to simulate the microenvironment of human HCC (19).In this study, we aimed to investigate whether quantitative parameters in DCE-MRI can monitor the change in microvasculature of liver tumors at different time points after CA4P treatment.     

Imaging patterns of fatty liver in pediatric patients

Fatty liver can present as focal, diffuse, heterogeneous, and multinodular forms. Being familiar with various patterns of steatosis can enable correct diagnosis. In patients with equivocal findings on ultrasonography, magnetic resonance imaging can be used as a problem solving tool. New techniques are promising for diagnosis and follow-up. We review imaging patterns of steatosis and new quantitative methods such as proton density fat fraction and magnetic resonance elastography for diagnosis of nonalcoholic fatty liver disease in children.Nonalcoholic fatty liver disease (NAFLD) is as widely encountered in children as in adults, with an estimated prevalence of 9.6% (1). It occurs due to accumulation of triglyceride in hepatocytes without alcohol ingestion. Nonalcoholic steatohepatitis (NASH) was first defined in children in 1983 (2). NAFLD includes a broad range of clinicopathologic features ranging from simple steatosis (fat with inflammation and/or fibrosis), steatohepatitis/NASH to cirrhosis. Some other diseases of liver can also cause hepatic steatosis including hepatitis B and C, Wilson’s disease, α-1-antitrypsin deficiency, autoimmune hepatitis, drug-induced liver injury (valproate, methotrexate, tetracycline, amiodarone, and prednisone), and total parenteral nutrition (3). Furthermore, fatty liver is a risk factor for cirrhosis, diabetes, and cardiovascular disease.In clinical practice, the diagnosis of NAFLD is made by increased serum ALT and/or presence of enlarged echogenic liver in ultrasonography. Being overweight or obese, and/or insulin resistance are highly indicative but not absolutely necessary for diagnosing NAFLD (4). The gold standard for diagnosis is liver biopsy, which additionally provides semi-quantitative analysis of NASH damage in children (5). It is an expensive, invasive procedure with a risk of morbidity (0.06%–0.35%) and mortality (0.01%–0.1%) (6).The evaluation of liver fat in children via noninvasive imaging modalities is needed to avoid complications of biopsy and for follow-up. Main imaging modalities for the assessment of pediatric NAFLD are ultrasonography (US) and magnetic resonance imaging (MRI). Computed tomography is the other imaging method for liver fat assessment, but ionizing radiation is a major drawback in children (7). Assessment of fat accumulation may cause diagnostic dilemmas and confusion due to manifestations with unusual structural patterns and imaging appearance of the liver. This article reviews the histopathology of pediatric NAFLD, radiologic evaluation and different structural patterns of childhood NAFLD/NASH on US and MRI. We also discuss diagnostic pitfalls and briefly review new imaging techniques.     

Clinical,pathological, and imaging characteristics of primitive neuroectodermal tumors of the spine

Primitive neuroectodermal tumors (PNETs) located in the spine are extremely rare, and information concerning these tumors in the medical literature is limited to single case reports. This pictorial essay presents the clinical, pathological, and imaging characteristics of PNET of the spine.Primitive neuroectodermal tumors (PNETs) are malignant tumors thought to arise from the neural ectoderm and comprise undifferentiated small round cells (1–3). PNETs located in the spine are extremely rare, and information concerning these tumors in the medical literature is limited to single case reports (4–5). This pictorial essay presents the clinical, pathological, and imaging characteristics of PNET of the spine.