Update on advances in molecular PET in urological oncology

Integrated positron emission tomography/computed tomography (PET/CT) with 2-[¹⁸F]fluoro-2-deoxy-d-glucose (¹⁸F-FDG) has emerged as a powerful tool for the combined metabolic and anatomic evaluation of many cancers. In urological oncology, however, the use of ¹⁸F-FDG has been limited by a generally low tumor uptake, and physiological excretion of FDG through the urinary system. ¹⁸F-FDG PET/CT is useful when applied to specific indications in selected patients with urological malignancy. New radiotracers and positron emission tomography/magnetic resonance imaging (PET/MRI) are expected to further improve the performance of PET in uro-oncology.     

Retrospective review: usefulness of a number of imaging modalities including CT, MRI, technetium-99m pertechnetate scintigraphy, gallium-67 scintigraphy and F-18-FDG PET in the differentiation of benign from malignant parotid masses

Objective The aim of this study is to evaluate an imaging approach using computed tomography (CT), magnetic resonance imaging (MRI), technetium-99m pertechnetate scintigraphy (^99mTc pertechnetate scintigraphy), gallium-67 scintigraphy (⁶⁷Ga scintigraphy) and fluorine-18 fluorodeoxyglucose positron emission tomography (¹⁸F-FDG PET). Material and Methods We reviewed retrospectively 59 patients with parotid masses. CT, MRI,⁶⁷Ga scintigraphy,^99mTc pertechnetate scintigraphy, and¹⁸F-FDG PET were performed. Results All of the benign tumors had smooth margins on CT and MRI. Patients with inflammatory lesions and malignant lesions showed well-defined margins or ill-defined margins. All Warthin's tumors showed high technetium accumulation. Many of malignant tumors showed high FDG accumulation. Both pleomorphic adenomas and Warthin's tumors showed high accumulation in some cases on¹⁸F-FDG PET. Among 15 patients with pleomorphic adenoma, 14 patients showed marked hyperintensity relative to CSF on T2-weighted images and partial enhancement on contrast-enhanced T1-weighted images. Combination of several imaging modarity offered usefulness of differential diagnosis for parotid masses. Conclusion An efficient combination of imaging methods may be helpul for achieve the correct diagnosis.     

Incidental Bilateral Renal Oncocytoma in a Patient with Metastatic Carcinoma of Unknown Primary: a Pitfall on 18F-FDG PET/CT

Bilateral renal masses are uncommon but can raise a strong suspicion of primary or secondary malignancy, especially during the initial work-up of an oncology patient. Renal oncocytomas are benign renal tumors that are commonly discovered incidentally on diagnostic imaging with a small percentage occurring bilaterally. Although ¹⁸F-FDG uptake in renal oncocytomas has been described, a case of a bilateral ¹⁸F-FDG-avid renal oncocytoma has not been previously reported in the literature. A variety of malignant causes of bilateral ¹⁸F-FDG positive renal masses are known, however it is important to include this benign etiology in the differential diagnosis. We report an unusual case of an incidental bilateral renal oncocytoma evaluated with contrast enhanced CT and ¹⁸F-FDG PET/CT.     

Usefulness of <Superscript>18</Superscript>F-FDG PET/CT to Detect Metastatic Mucinous Adenocarcinoma Within an Inguinal Hernia

Metastatic mucinous adenocarcinoma in an inguinal hernia is a rare disease and the image findings of ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography (PET)/computed tomography (CT) are little known. Here, we introduce a 57-year-old man with metastatic mucinous adenocarcinoma in an inguinal hernia. On initial ¹⁸F-FDG PET/CT, hypermetabolism was observed in mucinous adenocarcinoma of the cecum, and adenocarcinomas of the transverse and ascending colon, respectively. Follow-up ¹⁸F-FDG PET/CT revealed newly developed multiple hypermetabolism in peritoneal seeding masses and nodules in the pelvic cavity and scrotum. Peritoneal carcinomatosis in the right pelvic side wall was extended to the incarcerated peritoneum and mesentery in the right inguinoscrotal hernia.¹⁸F-FDG PET/CT was useful to reveal unexpected peritoneal seeding within the inguinal hernia. Also, this case demonstrated that metastatic mucinous adenocarcinomas had variably intense FDG uptake.     

Small Cell Carcinoma of the Gallbladder: 18F-FDG PET/CT Imaging Features—A Case Report

The diagnostic role of ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography (PET)/computed tomography (CT) for gallbladder small cell carcinoma has not been reported. A knowledge of the imaging characteristic features of this malignancy can be useful. Here we report a rare case of a patient who had various diagnostic imaging modalities, including ¹⁸F-FDG PET/CT.     

Pictorial review of <Superscript>18</Superscript>F-FDG PET/CT findings in musculoskeletal lesions

We herein reviewed ¹⁸F-fluoro-2-deoxyglucose (¹⁸F-FDG) positron emission tomography (PET)/computed tomography (CT) findings in a number of musculoskeletal lesions including malignant tumors, benign tumors, and tumor-like lesions with correlations to other radiographic imaging modalities, and described the diversity of the ¹⁸F-FDG PET/CT findings of this entity. Malignant primary musculoskeletal tumors are typically ¹⁸F-FDG avid, whereas low-grade malignant tumors show mild uptake. Benign musculoskeletal tumors generally show a faint uptake of ¹⁸F-FDG, and tumor-like conditions also display various uptake patterns of ¹⁸F-FDG. Although musculoskeletal tumors show various uptakes of ¹⁸F-FDG on PET/CT, its addition to morphological imaging modalities such as CT and MRI is useful for the characterization and differentiation of musculoskeletal lesions.     

Value of 18F-FDG PET/CT in the Detection of Ovarian Malignancy

Purpose

Ovarian cancer is a leading cause of gynecologic malignancy. As symptoms of ovarian cancer are nonspecific, only 20 % of ovarian cancers are diagnosed while they are still limited to the ovaries. Thus, early and accurate detection of disease is important for an improved prognosis. For the accurate and effective diagnosis of ovarian malignancy on ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography/computed tomography (PET/CT), we analyzed several parameters, including visual assessment.

Method

A total of 51 peritoneal lesions in 19 patients who showed ovarian masses with diffuse peritoneal infiltration were enrolled. Twelve patients were confirmed to have ovarian malignancy and seven patients with benign disease by pathologic examination. All patients were examined by ¹⁸F-FDG PET/CT, and an additional 2-h delayed ¹⁸F-FDG PET/CT was also performed for 15 patients with 42 peritoneal lesions. We measured semiquantitative parameters including maximum and mean standardized uptake values (SUVmax, SUVmean), metabolic tumor volume (MTV), and total lesion glycolysis (TLG) on a 1-h initial ¹⁸F-FDG PET/CT image (Parameter₁) and on a 2-h delayed image (Parameter₂). Additionally, retention indices of each parameter were calculated, and each parameter among the malignant and benign lesions was compared by Mann-Whitney U test. We also assessed the visual characteristics of each peritoneal lesion, including metabolic extent, intensity, shape, heterogeneity, and total visual score. Associations between visual grades and malignancy were analyzed using linear by linear association methods. Moreover, a receiver operating characteristic (ROC) curve was analyzed to compare the effectiveness of significant parameters.

Result

In a comparison between the malignant and benign groups in the analysis of 51 total peritoneal lesions, SUVmax₁, SUVmean₁, and TLG₁ showed significant differences. Also, in the analysis of 42 peritoneal lesions that underwent an additional 2-h ¹⁸F-FDG PET/CT examination, SUVmax_1,2, SUVmean_1,2, TLG₂, and the RI of TLG showed significant differences between the malignant and benign groups. MTV did not show significant differences in either the analysis of 51 peritoneal lesions or of 42 lesions. Regarding visual assessments, metabolic intensity, shape, heterogeneity, and total visual score showed an association with malignancy. In the ROC analysis, the AUC of the visual score was larger than the AUC of other parameters in both the analyses of 51 peritoneal lesions and of 42 lesions.

Conclusion

Although further study with a larger patient population is needed, the visual assessment of ¹⁸F-FDG PET/CT imaging has a primary role in the detection of malignancy in ovarian cancer patients with assistance from other semi-quantitative parameters.     

Lung Adenocarcinoma Staged as an Unknown Primary Presenting with Symptomatic Colon Metastases: Staging by 18F-FDG PET/CT

A 66-year-old man, who presented with bright red blood per rectum, was referred for an ¹⁸F-FDG PET/CT after colonoscopy showed two suspicious colon masses, which were biopsied to reveal an adenocarcinoma of unknown origin. PET/CT showed two intensely FDG-avid colon masses as well as an unsuspected FDG-avid lung mass, which was biopsied to reveal a primary lung adenocarcinoma. Immunohistochemistry confirmed the two colon metastases were of pulmonary origin. It is extremely rare for lung carcinoma to present with symptomatic colon metastases, with only 11 cases described in the literature. We report the first case of the utility of ¹⁸F-FDG PET/CT in staging a patient who presented with symptomatic colon metastases of an unknown primary lung malignancy.     

Clinical significance of 18F-α-methyl tyrosine PET/CT for the detection of bone marrow invasion in patients with oral squamous cell carcinoma: comparison with 18F-FDG PET/CT and MRI

Objective

L-3-[¹⁸F]-fluoro-α-methyl tyrosine (¹⁸F-FAMT) is an amino acid tracer for positron emission tomography/computed tomography (PET/CT) which specifically transported into cancer cells by L-type amino acid transporter 1 (LAT1). LAT1 overexpression in tumors is significantly correlated with cell proliferation and angiogenesis. ¹⁸F-FAMT PET/CT, fluorine-18-fluorodeoxyglucose (¹⁸F-FDG) PET/CT and magnetic resonance imaging (MRI) were compared for their diagnostic performance in the detection of bone marrow invasion in patients with oral squamous cell carcinoma (OSCC).

Methods

Twenty-seven patients with OSCC on the upper or lower alveolar ridge underwent staging by MRI, ¹⁸F-FDG PET/CT and ¹⁸F-FAMT PET/CT studies before surgery. Post-surgical pathologic examination was used as the standard to determine the final diagnoses. The possibility of bone marrow invasion on MRI, ¹⁸F-FDG PET/CT and ¹⁸F-FAMT PET/CT were usually graded retrospectively into five-point score. Sensitivity, specificity, accuracy, positive predictive value (PPV) and negative predictive value (NPV) were calculated according to the obtained scores.

Results

As the sensitivity of ¹⁸F-FDG PET/CT was highest (100 %) among that of MRI (95 %) and ¹⁸F-FAMT PET/CT (90 %), the specificity of ¹⁸F-FAMT PET/CT was highest (85.7 %) among that of MRI (57 %) and ¹⁸F-FDG PET/CT (14.3 %). The size of pathological tumor was accorded with that detected by ¹⁸F-FAMT PET/CT and was smaller than that detected by ¹⁸F-FDG PET/CT (P < 0.01). Significant difference was not found between ¹⁸F-FAMT PET tumor volume and pathological tumor volume.

Conclusions

¹⁸F-FAMT PET/CT was useful and more specific than MRI or ¹⁸F-FDG PET/CT in the detection of bone marrow invasion of OSCC and may contribute to minimize the extent of resection in oral surgery patient.     

Diagnostic value of combined 18F-FDG PET/MRI for staging and restaging in paediatric oncology

Purpose

The present study compares the diagnostic value of ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET) and MRI to combined/registered ¹⁸F-FDG PET/MRI for staging and restaging in paediatric oncology.

Methods

Over 8?years and 2?months, 270 ¹⁸F-FDG PET and 270 MRI examinations (mean interval 5?days) were performed in 132 patients with proven (n?=?117) or suspected (n?=?15) malignant disease: solid tumours (n?=?64), systemic malignancy (n?=?53) and benign disease (n?=?15). A total of 259 suspected tumour lesions were analysed retrospectively during primary diagnosis and 554 lesions during follow-up. Image analysis was performed separately on each modality, followed by analysis of combined and registered ¹⁸F-FDG PET/MRI imaging.

Results

A total of 813 lesions were evaluated and confirmed by histopathology (n?=?158) and/or imaging follow-up (n?=?655) after 6?months. In the separate analysis of ¹⁸F-FDG PET and MRI, sensitivity was 86?%/94?% and specificity 85?%/38?%. Combined/registered ¹⁸F-FDG PET/MRI led to a sensitivity of 97?%/97?% and specificity of 81?%/82?%. False-positive results (¹⁸F-FDG PET n?=?69, MRI n?=?281, combined ¹⁸F-FDG PET/MRI n?=?85, registered ¹⁸F-FDG PET/MRI n?=?80) were due to physiological uptake or post-therapeutic changes. False-negative results (¹⁸F-FDG PET n?=?50, MRI n?=?20, combined ¹⁸F-FDG PET/MRI n?=?11, registered ¹⁸F-FDG PET/MRI n?=?11) were based on low uptake or minimal morphological changes. Examination-based evaluation during follow-up showed a sensitivity/specificity of 91?%/81?% for ¹⁸F-FDG PET, 93?%/30?% for MRI and 96?%/72?% for combined ¹⁸F-FDG PET/MRI.

Conclusion

For the detection of single tumour lesions, registered ¹⁸F-FDG PET/MRI proved to be the methodology of choice for adequate tumour staging. In the examination-based evaluation, MRI alone performed better than ¹⁸F-FDG PET and combined/registered imaging during primary diagnosis. At follow-up, however, the examination-based evaluation demonstrated a superiority of ¹⁸F-FDG PET alone.     

Ovarian Mass Mimicking Malignancy: A Case Report

A 32-year-old female who suffered from abdominal pain underwent ¹⁸F-fluorodexoyglucose (FDG) positron emission tomography/computed tomography (PET/CT) for the diagnostic workup of pelvic mass lesions. Cystic mass lesions in the bilateral ovaries showed wall thickening and intense hypermetabolism along the rim. In addition, multifocal intense hypermetabolic lymphadenopathies were seen in the left paraaortic lymph node (LN), aortocaval LN, and both common iliac LNs. We interpreted these findings as bilateral ovarian cancer with retroperitoneal metastatic lymphadenopathies rather than endometriosis with reactive lymphadenopathies. However, histopathological examination confirmed the ovarian mass lesions as tubo-ovarian abscesses. We report a case that even if simultaneous hypermetabolic retroperitoneal LNs are seen, intense hypermetabolic lesions in both ovaries can be in consequence of inflammatory change.     

<Superscript>18</Superscript>F-fluorodeoxyglucose positron emission tomography in uterine carcinosarcoma

Purpose Uterine carcinosarcomas clinically confined to the uterus usually harbor occult metastases. We conducted a pilot study to evaluate the value of ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET) in uterine carcinosarcoma. Methods Patients with histologically confirmed uterine carcinosarcoma were enrolled. Abdominal and pelvic magnetic resonance imaging (MRI)/whole-body computed tomography (CT) scan, and whole-body ¹⁸F-FDG PET or PET/CT were undertaken for primary staging, evaluating response, and restaging/post-therapy surveillance. The clinical impact of ¹⁸F-FDG PET was determined on a scan basis. Results A total of 19 patients were recruited and 31 ¹⁸F-FDG PET scans (including 8 scans performed on a PET/CT scanner) were performed. Positive impacts of scans were found in 36.8% (7/19) for primary staging, 66.7% (2/3) for monitoring response, and 11.1% (1/9) for restaging/post-therapy surveillance. PET excluded falsely inoperable disease defined by MRI in two patients. Aggressive treatment applying to three patients with PET-defined resectable stage IVB disease seemed futile. Two patients died of disease shortly after salvage therapy restaged by PET. With PET monitoring, one stage IVB patient treated by targeted therapy only was alive with good performance. Using PET did not lead to improvement of overall survival of this series compared with the historical control (n = 35) (P = 0.779). Conclusions The preliminary results suggest that ¹⁸F-FDG PET is beneficial in excluding falsely inoperable disease for curative therapy and in making a decision on palliation for better quality of life instead of aggressive treatment under the guidance of PET. PET seems to have limited value in post-therapy surveillance or restaging after failure.     

Role of 18F-FDG PET/CT in the assessment of bone involvement in newly diagnosed multiple myeloma: preliminary results

Purpose Multiple myeloma (MM) is a malignant B cell and plasma cell disorder which involves the skeleton in more than 80% of patients at diagnosis. The aim of this study was to compare whole-body X-ray (WBXR), MRI and ¹⁸F-FDG PET/CT in patients with MM. Methods The study population comprised 28 newly diagnosed MM patients. Findings of ¹⁸F-FDG PET/CT were compared with those of WBXR and MRI with regard to the number and site of lesions detected. Results Comparing ¹⁸F-FDG PET/CT and WBXR, it was found that in 16/28 pts (57%) ¹⁸F-FDG PET/CT detected more lesions, all of which were located in the skeleton. Nine of these 16 patients had a completely negative WBXR survey. In 12/28 pts (43%) the two methods yielded equivalent findings. Comparing ¹⁸F-FDG PET/CT and MRI, it was found that in 7/28 pts (25%), ¹⁸F-FDG PET/CT detected more lytic bone lesions, all of which were located outside the field of view of MRI (bone lesions in six cases and a soft tissue lesion in one). In 14/28 pts (50%), ¹⁸F-FDG PET/CT and MRI detected the same number of lesions in the spine and pelvis, while in 7/28 pts (25%) MRI detected an infiltrative pattern in the spine whereas ¹⁸F-FDG PET/CT was negative. Conclusion ¹⁸F-FDG PET/CT appears to be more sensitive than WBXR for the detection of small lytic bone lesions, whereas it has the same sensitivity as MRI in detecting bone disease of the spine and pelvis. On the other hand, MRI may be superior to ¹⁸F-FDG PET/CT in diagnosing an infiltrative pattern in the spine. Therefore, careful evaluation of MM bone disease at diagnosis should include both MRI of the spine and ¹⁸F-FDG PET/CT.     

18F-FDG PET/CT in detection of gynecomastia in patients with hepatocellular carcinoma

ObjectiveWe retrospectively investigate the prevalence of gynecomastia as false-positive 2-[¹⁸F]fluoro-2-deoxy-d-glucose (¹⁸F-FDG) positron emission tomography (PET)/computed tomography (CT) imaging in patients with hepatocellular carcinoma (HCC).MethodsAmong the 127 male HCC patients who underwent ¹⁸F-FDG PET/CT scan, the ¹⁸FDG uptakes at the bilateral breasts in 9 patients with gynecomastia were recorded as standard uptake value (SUVmax) and the visual interpretation in both early and delayed images.ResultsThe mean early SUVmax was 1.58/1.57 (right/left breast) in nine gynecomastia patients. The three patients with early visual score of 3 had higher early SUVmaxs.ConclusionGynecomastia is a possible cause of false-positive uptake on ¹⁸F-FDG PET/CT images.     

Siliconomas mimicking cancer

Introduction

Silicone breast implants are widely used for breast augmentation and breast reconstruction following mastectomy. Implant rupture has specific radiological signs. With the advent use of new imaging technique such as positron emission tomography (PET) computed tomography (CT) and magnetic resonance imaging (MRI) of the breast, these signs may simulate malignancy.

Patients and methods

We retrospectively reviewed four cases of patients with silicon breast implants who arrive to the mammography clinic for further evaluation of a suspected malignant process demonstrated on either PET CT or breast MRI.

Results

Two cases were of PET CT performed for routine oncology follow-up of breast cancer. On both, the PET CT demonstrated multiple-spread benign silicone granulomas manifesting as multiple masses having an increase fluorodeoxyglucose (FDG) uptake. One case of a new mass was demonstrated as a suspicious mass on the dynamic sequences on MRI of the breast. Ultrasound-guided biopsy demonstrated benign tissue response to silicone. One case demonstrated bilateral ruptured breast implants on breast MRI, as well as bilateral axillary and mediastinal lymphadenopathy. Eventually, the patient underwent bronchoscopy for pulmonary workup of dry cough, revealing sarcoidosis.

Conclusion

Silicone granulomas can manifest as masses with suspicious morphology and enhancement dynamics on breast MRI or with increased FDG uptake on PET CT. The presence of silicone implants and awareness of the possibility of a rupture and formation of silicone granulomas may help in facilitating a correct diagnosis.     

Imaging findings of primary malignant gastrointestinal stromal tumor of the liver

A primary gastrointestinal stromal tumor (GIST) arising in the liver is extremely rare. In our case of GIST, CT and MRI showed a well-defined, weakly enhancing mass with a cystic component in the left lateral segment of the liver that showed homogeneous and avid ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) accumulation on positron emission tomography/computed tomography (PET/CT). We herein present a rare case of primary malignant GIST of the liver presenting with peritoneal seeding on CT, gadoxetic acid-enhanced MRI and ¹⁸F-FDG PET/CT.     

Pitfalls and Misinterpretations of Cardiac Findings on PET/CT Imaging: A Careful Look at the Heart in Oncology Patients

Positron emission tomography (PET) computed tomography (CT) with 2-[fluorine-18] fluoro-2-deoxy-d-glucose (FDG) has been established as an effective modality for evaluation of cancer. Interpretations of patterns of physiologic ¹⁸F-FDG uptake by the heart is particularly difficult given the wide normal variations of ¹⁸F-FDG metabolic activity observed. Atypical patterns of focal or diffuse physiologic cardiac ¹⁸F-FDG uptake and post-therapeutic effects after radiation therapy, systemic diseases, or cardiomyopathy may also be confused with malignant disease on ¹⁸F-FDG PET/CT. In this article, we review the variations of normal cardiac ¹⁸F-FDG uptake observed in oncology patients and the appearances of other patterns of pathologic metabolic activity, related or not related to the malignancy being investigated, that may lead to false-negative and false-positive results.     

Present and future roles of FDG-PET/CT imaging in the management of lung cancer

Integrated positron emission tomography/computed tomography (PET/CT) using 2-[¹⁸F]fluoro-2-deoxy-d-glucose (¹⁸F-FDG) has emerged as a powerful tool for combined metabolic and anatomic evaluation in clinical oncologic imaging. This review discusses the utility of ¹⁸F-FDG PET/CT as a tool for managing patients with lung cancer. We discuss different patient management stages, including diagnosis, initial staging, therapy planning, early treatment response assessment, re-staging, and prognosis.     

<Superscript>68</Superscript>Gallium-Arginine-Glycine-Aspartic Acid and <Superscript>18</Superscript>F-Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography in Chondroblastic Osteosarcoma of the Skull

We report the case of a 32 year-old male with Chondroblastic Osteosarcoma of the skull, which was imaged with both ¹⁸[F]fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography/computed tomography (PET/CT) and ⁶⁸Gallium-arginine-glycine-aspartic acid (⁶⁸Ga-RGD) PET/CT. The ¹⁸F-FDG PET/CT did not demonstrate the tumour, whereas the ⁶⁸Ga-RGD PET/CT clearly depicted a left-sided frontal tumour. ⁶⁸Ga-RGD PET/CT may be a clinically useful imaging modality for early detection of recurrent osteosarcoma, considering the limitations of ¹⁸F-FDG PET in a setting of low glycolytic activity.     

A case of septic pulmonary embolism associated with renal abscess mimicking pulmonary metastases of renal malignancy

We report the case of a 46-year-old woman with acute febrile symptom who had multiple pulmonary nodules and a renal mass. She underwent ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) to find a hidden malignancy and the cause of her fever. FDG PET/CT images demonstrated a renal mass and multiple lung nodules with intense FDG uptake, which was suspicious of a renal malignancy with multiple pulmonary metastatic lesions. CT-guided biopsies of the pulmonary and renal lesions only showed chronic inflammatory infiltrates without evidence of malignancy. She was diagnosed with septic pulmonary embolism from a renal abscess. One month after antibiotic treatment, the follow-up chest and abdomen CT showed improvement of the lung and renal lesions. This is the first case demonstrating the FDG PET/CT finding of septic pulmonary embolism associated with renal abscess in the published literature.