The use of whole-body fluorine-18-fluorodeoxyglucose positron emission tomography integrated with computed tomography for accurate staging and surveillance in the case of mucosa-associated lymphoid tissue

We present the case of a 79-year-old male, who was initially treated for mucosa-associated lymphoid tissue lymphoma (MALT lymphoma) of the right eyelid, and later for disease relapse in the stomach. During follow up, he was noted to have developed left arm nodules just medial to the proximal biceps muscle, which were found to be multiply enlarged lymph nodes on subsequent ultrasound imaging. Excisional biopsy of these nodes revealed MALT lymphoma. He was initially referred for consideration of radiation, but a restaging F-18 fluorodeoxyglucose positron emission tomography integrated with computed tomography (F-18 FDG PET/CT) further identified a focus of suspicious uptake in left calf, which was later also biopsy proven to be MALT lymphoma. His disease was upstaged as the result of this later finding, and the overall recommendation for treatment changed to favor systemic treatment with Rituximab.     

FDG avidity and PET/CT patterns in primary gastric lymphoma

PURPOSE: The use of 18F-fluoro-deoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) in primary gastric lymphoma (PGL) is challenging due to physiologic FDG activity in the stomach and variability in the degree of uptake in various histologic subtypes. This study assesses FDG avidity and PET/CT patterns in newly diagnosed PGL. METHODS: Sixty-two PET/CT studies of newly diagnosed PGL were reviewed (24 low-grade mucosa-associated lymphoid tissue [MALT], 38 aggressive non-Hodgkin's lymphoma [AGNHL]). FDG avidity, patterns (focal/diffuse), and intensity (visually vs. the liver and SUVmax) were assessed and compared to 27 controls. Gastric CT abnormalities and extragastric sites were recorded. RESULTS: Gastric FDG uptake was found in 55/62 (89%) PGL (71% MALT vs. 100% AGNHL, p < 0.001) and 63% controls. A diffuse pattern was found in 60% PGL (76% MALT vs. 53% AGNHL, p = NS) and 47% controls. FDG uptake higher than liver was found in 82% PGL (58% MALT vs. 97% AGNHL, p < 0.05) and 63% controls. SUVmax in FDG-avid PGLs was 15.3 +/- 11.7 (5.4 +/- 2.9 MALT vs. 19.7 +/- 11.5 AGNHL, p < 0.001) and 4.6 +/- 1.4 in controls. CT abnormalities were found in 79% PGL (thickening, n = 49; ulcerations, n = 22). Extra-gastric FDG-avid sites were seen in none of MALT, but 61% of AGNHL (nodal, n = 18; nodal and extranodal, n = 5). CONCLUSIONS: FDG avidity was present in 89% of PGLs, including all patients with AGNHL but only 71% of MALT. FDG uptake can be differentiated, in particular in AGNHL-PGL, from physiologic tracer activity by intensity but not by pattern. Extragastric foci on PET and structural CT abnormalities are additional parameters that can improve PET/CT assessment of PGL. Defining FDG avidity and PET/CT patterns in AGNHL and a subgroup of MALT-PGL before treatment may be important for further monitoring therapy response.     

Clinical role of FDG PET/CT for methotrexate-related malignant lymphoma

Methotrexate-related malignant lymphoma (MTX-RML) is a type of therapy-related lymphoma, and it often occurs in patients with rheumatoid arthritis. The most distinctive characteristic of MTX-RML is a quick response to withdrawal of MTX. However, because there is a risk of recurrence without a distinctive indicator of disease, close follow-up is needed. We present F-18 2-fluoro-2-deoxyglucose (FDG) postitron emission tomography (PET) or computed tomography (CT) images of MTX-RML along with the characteristic clinical presentation of MTX-RML. FDG PET/CT has the advantage of being able to detect malignant lymphoma in patients who have undergone MTX treatment. After withdrawal of MTX, FDG uptake decreases along with a reduction in the volume of lesions. Although recurrent lesion develops independent to the initial FDG PET/CT findings, FDG PET/CT is useful for early detection of unexpected recurrent lesions. FDG PET/CT allows for the assessment of malignant lymphoma and recurrent lesions in patients who received MTX therapy, which is crucial for the management of MTX-RML.     

Cerebral Toxoplasmosis in a Patient with AIDS on F-18 FDG PET/CT

The distinction between primary central nervous system (CNS) lymphoma and nonmalignant lesions due to opportunistic infections, in particular cerebral toxoplasmosis, is important because of the different treatments involved. A 32-year-old patient with AIDS was hospitalized for intermittent headaches. Brain magnetic resonance imaging (MRI) showed a small well-enhanced nodular lesion in the right frontal lobe. A fluorine-18 fluorodeoxyglucose (F-18 FDG) positron emission tomography (PET)/computed tomography (CT) scan showed moderate FDG uptake in the nodular lesion of the right frontal lobe. We present a case of cerebral toxoplasmosis in a patient with acquired immunodeficiency syndrome (AIDS) and the usefulness of F-18 FDG PET/CT in the differential diagnosis of the cerebral toxoplasmosis will be discussed.     

F-18 FDG PET/CT imaging of low-grade mucoepidermoid carcinoma of the bronchus

Mucoepidermoid carcinomas in the bronchial tree are extremely rare tumors. Such tumors are classified into low-grade and high-grade on the basis of histological criteria. Fluorine-18-fluorodeoxyglucose positron emission tomography (F-18 FDG PET) is a useful technique for the evaluation of pulmonary lesions; however, to our knowledge, F-18 FDG PET findings in mucoepidermoid carcinoma of the bronchus have been described in only a few cases. Identifiable focal F-18 FDG uptake has been reported in high-grade mucoepidermoid carcinoma, but it is unclear whether F-18 FDG accumulates in low-grade mucoepidermoid carcinoma. Here, we present the case of a 37-year-old woman, with pathologically proven low-grade mucoepidermoid carcinoma, who underwent high-resolution computed tomography (CT) and F-18 FDG PET/CT before treatment.     

Nonossifying fibroma can mimic residual lymphoma in FDG PET: additional value of combined PET/CT

A 12-year-old girl was diagnosed with Hodgkin's lymphoma and underwent conventional cross-sectional imaging for initial staging. Chemotherapy was given according to standard pediatric protocols. At the end of therapy, an F-18 FDG PET/CT examination was performed to evaluate the therapeutic response. The scan demonstrated focal uptake of FDG in the right distal femur and residual lymphoma was taken into consideration. However, findings in the coregistered CT scan were consistent with nonossfiying fibroma, a common benign skeletal lesion. Combined PET/CT imaging can be helpful to identify benign bone lesions mimicking metastatic or residual disease in F-18 FDG PET as illustrated by this case.     

Conjunctival lymphoma can be detected by FDG PET

Four consecutive patients presented with extranodal marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma) in the conjunctiva. After the initial resection, long-term follow-up without additional therapy showed the clinical relapse. Fluorodeoxyglucose positron emission tomography fused with computed tomography (PET/CT) showed abnormal uptake in the conjunctival relapsed lesions, which were, on reresection, again proven as MALT lymphoma. Small and thin lesions of MALT lymphoma in the conjunctiva can be detected by fluorodeoxyglucose PET/CT. The resolution of PET/CT, delineated in this study, could be applied to the other areas of the body to achieve more accurate staging of lymphoma.     

Abdominal Mesh Implant Showing FDG Uptake on PET/CT

F-18 fluorodeoxyglucose (FDG) uptake by a mesh implant might be caused by a foreign body granulomatous reaction with inflammation and fibrosis, which can be demonstrated by positron emission tomography/computed tomography (PET/CT). A 71-year-old man underwent F-18 FDG PET/CT for the follow-up evaluation after an operation for colonic adenocarcinoma. On PET/CT imaging, there was a rectangular-shaped FDG uptake (maximal standardized uptake value, maxSUV: 3.4) in the anterior abdominal wall. On the review of the medical records, the patient had a history of herniorrhapy for the reinforcement of the abdominal wall 2 months previously, using a mesh implant consisting of polytetrafluoroethylene (Teflon). We report a case of FDG uptake associated with surgical procedures including mesh implant on F-18 FDG PET/CT.     

Benign Schwannoma Mimicking Metastatic Lesion on F-18 FDG PET/CT in Differentiated Thyroid Cancer

We report a case of benign schwannoma mimicking metastatic carcinoma. A 55-year-old female with papillary thyroid carcinoma underwent total thyroidectomy. F-18 fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) demonstrated a focal hypermetabolic lesion with maximum standardized uptake value (SUVmax) 5.3 at the right chest wall. Conventional chest CT demonstrated a 5.4 cm ovoid mass lesion between the intercostal muscles and liver. Pathology revealed a schwannoma by tumor excision. This case demonstrates that benign schwannoma may demonstrate FDG uptake mimicking metastatic carcinoma.     

18F-FDG PET in malignant lymphoma: significance of positive findings

Purpose The aim of this study was to evaluate the significance of increased uptake of ¹⁸F-fluorodeoxyglucose (FDG) in patients with malignant lymphoma (ML) studied by positron emission tomography (PET).Methods A total of 1,120 consecutive scans carried out in 848 patients were reviewed; all patients had a diagnosis of ML [574 non-Hodgkins lymphoma (NHL) and 274 Hodgkins disease (HD)] and were studied at completion of therapy, for suspected recurrence or during follow-up. PET was carried out after intravenous injection of 370 MBq of ¹⁸F-FDG; images were recorded after 60–90 min. Patients were selected whose reports indicated areas of increased FDG uptake. PET findings were considered positive for lymphomatous localisation when uptake occurred at sites of previous disease, in asymmetrical lymph nodes or in nodes unlikely to be affected by inflammation (mediastinal, except for hilar, and abdominal). PET findings were adjudged negative for neoplastic localisations in the following instances: physiological uptake (urinary, muscular, thymic or gastrointestinal in patients without MALT), symmetrical nodal uptake, uptake in lesions unrelated to lymphoma that had already been identified by other imaging methods at the time of PET scan, uptake at sites atypical for lymphoma, very low uptake and non-focal uptake. PET findings were compared with the results of other diagnostic procedures (including CT and ultrasound), biopsy findings and follow-up data.Results Overall, 354 scans (in 256 patients) showed increased FDG uptake (244 scans in NHL and 110 in HD): in 286 cases, FDG uptake was considered pathological and indicative of ML, in 41 cases the findings were described as uncertain or equivocal and in 37 cases, FDG uptake was considered unrelated to ML (in ten scans, concurrent findings of abnormal FDG uptake attributed to ML and uptake assigned to other causes were obtained) . Of the 286 patients with positive PET findings, 274 (95.8%) were found to have residual or recurrent ML (i.e. true positives). Four of the 41 patients with inconclusive findings turned out to have ML, while in 13 patients, pathological processes other than ML could be identified as the cause of FDG uptake. ML was excluded in all patients with findings reported as non-pathological (100% true-negative rate). Therefore, the false-positive rate in our series was about 5%. The main cause of increased FDG uptake mimicking ML was inflammation.Conclusion Our data confirm that ¹⁸F-FDG-PET has very high but not absolute specificity for ML. As already suggested, increased FDG uptake may also be observed in patients without active disease; in most cases, however, non-pathological FDG accumulation is properly identified. Less frequently, inconclusive scans are encountered; these cases are usually caused by inflammation, which subsequently resolves.     

Fat necrosis mimicking B-cell lymphoma: a PET/CT and FDG study

F-18 fluoro-2-deoxyglucose positron emission tomography combined with computed tomography (FDG and PET/CT) is increasingly becoming the standard in staging and restaging patients with a range of malignancies including B-cell lymphoma. However, there are well-known pitfalls in PET/CT with FDG imaging, which comprise infection, inflammation, physiological variants, and benign pathologic conditions. Fat necrosis is the result of death of adipose tissue from disease, injury, or pathologic conditions. We describe a case of false positive PET/CT and FDG scan in a patient with fat necrosis mimicking B-cell lymphoma after 6 cycles of rituximab with cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP) treatment. In interpreting PET/CT and FDG images with inconsistency in lesion response, fat necrosis should be considered in the differential diagnosis.     

Sagittal sinus tumor thrombosis in a case of NHL demonstrated on F-18 FDG PET/CT

We report a case of a 60-year-old woman, diagnosed as a case of non Hodgkins lymphoma (NHL), referred for F-18 fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) following 6 cycles of chemotherapy to evaluate response to therapy. The scan revealed a curvilinear pattern of FDG accumulation in the midline extending anteroposteriorly, just adjacent to the inner table of the skull on the fused PET/CT images with no corresponding abnormality on the low-dose CT. Because this site anatomically corresponded to that of the sagittal sinus, an MRI and magnetic resonance venography was advised which confirmed the presence of sagittal sinus tumor deposits. This case highlights the pattern of sagittal sinus tumor thrombosis on FDG PET/CT and the possibility of its occurrence in NHL.     

Acute varicella infection mimics recurrent Hodgkin's disease on F-18 FDG PET/CT

We report a case where acute varicella infection, chickenpox, mimics the findings of recurrent Hodgkin disease on F-18 FDG PET/CT. A 28-year-old man with a history of Hodgkin disease in remission had fatigue, pyrexia, and a raised ESR. His F-18 FDG PET/CT, performed to exclude lymphoma recurrence, demonstrated FDG-avid lymphadenopathy and increased FDG uptake in his spleen. A day later he developed the generalized rash of acute varicella infection. This was managed with valacyclovir. Repeat F-18 FDG PET/CT done 1 month later showed no evidence of FDG-avid disease. In this patient the stimulation of an immune response by the acute viral infection mimics recurrent lymphoma.     

Incidentally Detected Small Intestine Intussusception Caused by Primary Small Intestine Carcinoma on <Superscript>18</Superscript>F-FDG PET/CT

Small intestine intussusception in adults is a rare condition mainly caused by primary or metastatic small intestine malignancy. Here, we present a 72-year-old male patient who was diagnosed with small intestine cancer that was presented as small intestine intussusception on hybrid ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT). The patient was initially referred for an abnormality on a chest radiography and severe anemia. FDG PET/CT showed the lung lesion in the right upper lobe of lung as a high FDG uptake mass. Accidentally, FDG PET demonstrated another intense hypermetabolic intraluminal lesion in the small intestine accompanied with intussusception shown as a circumferential hypermetabolic wall. By pathologic examination, the patient was diagnosed as primary small intestine cancer with lung metastasis. This case highlights usefulness of hybrid FDG PET/CT to identify unexpected malignancy.     

Intravascular large B-cell lymphoma with diffuse FDG uptake in the lung by 18FDG-PET/CT without chest CT findings

We report a rare case of intravascular large B-cell lymphoma (IVLBCL) with diffuse fluorodeoxyglucose (FDG) uptake in the lung by (18)FDG-positron emission tomography/computed tomography (PET/CT). CT showed nodular shadow, whereas diffuse FDG uptake in PET/CT suggested IVLBCL in the lung. A random skin biopsy provided histological evidence of IVLBCL. The patient responded well to combination chemotherapy. Only two cases of IVLBCL in which diffuse pulmonary FDG uptake was demonstrated have been reported previously. FDG-PET/CT plus random skin biopsy may be useful for the early diagnosis of IVLBCL with pulmonary involvement even without convincing radiological findings in the lung.     

惰性淋巴瘤大细胞转化的~(18)F-FDG PET/CT影像研究(附8例分析)

目的:探讨~(18)F-FDG PET/CT对惰性淋巴瘤大细胞转化的诊断价值.方法:回顾性分析8例惰性淋巴瘤转化前后~(18)F-FDG PET/CT影像,其中男性5例,女性3例,平均年龄53.5岁;8例转化前后均经病理及免疫组化染色证实.结果:8例惰性淋巴瘤最终均转化为弥漫大B细胞型淋巴瘤;其中6例由黏膜相关淋巴组织边缘区B细胞淋巴瘤(MALT)转化;1例由滤泡性淋巴瘤(FL)转化;1例由霍奇金结节性淋巴细胞为主性淋巴瘤(NLPHL)转化.转化前病灶~(18)F-FDG摄取呈轻度增高或无增高,平均SUV为2.2±1.0;转化后病灶~(18)F-FDG摄取明显增高,平均SUV为4.7±1.9;转化后病灶平均SUV明显高于转化前(P<0.01).结论:惰性淋巴瘤以小细胞为主,其增殖活性低,核分裂不明显,葡萄糖代谢水平较低,在PET/CT上病灶呈低摄取;转化成大细胞淋巴瘤增殖活性高,核分裂明显,葡萄糖代谢水平明显增高,提示~(18)F-FDG PET/CT随访可帮助判断惰性淋巴瘤发生大细胞转化.     

Hodgkin disease: diagnostic value of FDG PET/CT after first-line therapy--is biopsy of FDG-avid lesions still needed?

PURPOSE: To retrospectively determine the sensitivity and specificity of co-registered fluorine 18 fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) in patients with Hodgkin lymphoma after first-line therapy, with use of clinical follow-up or biopsy results as the reference standard. MATERIALS AND METHODS: Informed consent was obtained for imaging and included consent to use patient data for research purposes. Institutional review board approval was obtained. Between May 2001 and July 2005, the data for all patients (n=66) at the authors' institution with proved Hodgkin lymphoma after first-line therapy were retrospectively reviewed. PET/CT scans were evaluated for the presence of abnormal FDG uptake and residual masses after the end of treatment and at further follow-up. All patients with pathologic FDG lesions underwent surgical biopsy for histopathologic confirmation. All patients with negative PET/CT scans at follow-up were evaluated for disease-free survival. RESULTS: An FDG-avid lesion was detected at PET/CT in 27 of the 66 patients (mean age +/- standard deviation, 33.0 years +/- 12.2). Recurrence of Hodgkin lymphoma was confirmed with biopsy in 23 of the 27 patients. The mean maximum standardized uptake value (SUV) of the histopathologically proved lesions was 7.32 (+/-2.01). Four patients had false-positive findings at PET/CT: Biopsy revealed only inflammatory changes, and the mean maximum SUV was 7.30 (+/-2.53). Thirty-nine patients (mean age, 36.7 years +/- 10.8) did not have FDG-avid lesions and remained free of disease after a mean clinical follow-up of 26.2 months (+/-12.5) (specificity, 91% [39 of 43 patients]; sensitivity, 100% [23 of 23 patients]). The presence of bulky disease (>5 cm) after the end of treatment was a significant predictor of recurrent disease (P<.05). CONCLUSION: The authors conclude that FDG PET/CT can help exclude persistent and/or recurrent Hodgkin lymphoma after first-line therapy. Because of the false-positive results and the toxicity of salvage chemotherapy, including high-dose chemotherapy with autologous stem cell support, biopsy of the FDG-avid lesion is still needed.     

Unusual Horner’s Syndrome in Recurrent Breast Cancer: Evaluation Using <Superscript>18</Superscript>F-FDG PET/CT

¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) is a widely used imaging modality in the initial diagnosis of cancer, treatment response evaluation and detection of recurrence. Herein, we present the case of a 39-year-old female who presented right ptosis on the follow-up of breast cancer after surgery. Clinicians suspected Horner’s syndrome, and the patient underwent FDG PET/CT for the evaluation of recurrence that could cause Horner’s syndrome. FDG PET/CT demonstrated a focal hypermetabolic lesion in the right cervicothoracic junction area, corresponding to the preganglionic cervical sympathetic trunk. A subsequent needle biopsy was done, and the lesion was confirmed as metastatic ductal carcinoma. In this case, we could detect the exact location of the recurring lesion that caused Horner’s syndrome using FDG PET/CT.     

18F-FDG PET/CT在肺黏膜相关淋巴组织淋巴瘤与炎症型非小细胞肺癌鉴别诊断中的价值

目的 探讨18F-氟脱氧葡萄糖（FDG） PET/CT的影像特征在肺黏膜相关淋巴组织（MALT）淋巴瘤及炎症型非小细胞肺癌（NSCLC）中的鉴别诊断价值。 方法 回顾性分析2015年1月至2020年12月于福建医科大学附属协和医院行18F-FDG PET/CT、肺部表现为类炎症改变并经组织病理学检查确诊的21例肺MALT淋巴瘤患者[男性13例、女性8例,年龄56~74（66.2±5.8）岁]及33例炎症型NSCLC患者[男性20例、女性13例,年龄48~84（64.6±9.6）岁]的临床资料。手动勾画CT及PET的感兴趣区,测量病变最大截面的长径及短径、CT值、最大标准化摄取值（SUV_max）和峰值标准化摄取值（SUV_peak）,分析影像征象（病变形态、支气管征、病变位置、淋巴结及脾脏的代谢情况）。采用χ2检验、独立样本t检验及校正t检验比较2组间的差异。 结果 21例肺MALT淋巴瘤患者中,肿块型少于实变型（28.6%对71.4%）,33例炎症型NSCLC患者中,肿块型多于实变型（57.6%对42.4%）,二者的差异有统计学意义（χ2=4.342,P=0.037）;肺MALT淋巴瘤患者中空气支气管征的比例高于炎症型NSCLC患者（90.5%对75.8%）,合并高代谢淋巴结的比例明显低于炎症型NSCLC（14.3%对48.5%）,二者的差异均无统计学意义（ χ2= 0.996、3.288,均 P>0.05）;肺MALT淋巴瘤患者中单侧发病的比例低于双侧发病（23.8%对85.7%）,炎症型NSCLC患者中,单侧发病的比例高于双侧发病（84.8%对15.2%）,二者的差异有统计学意义（χ2=26.133,P<0.001）;肺MALT淋巴瘤患者中脾脏高代谢者11例（52.4%）,炎症型NSCLC患者中未见脾脏高代谢者,二者的差异有统计学意义（χ2=21.708,P<0.001）。肺MALT淋巴瘤患者的长径和短径较炎症型NSCLC患者短 [（5.89±2.14） cm对（6.26±2.75） cm、（3.88±1.98） cm对（4.21±1.56） cm],二者的差异均无统计学意义（t=?1.46、?1.87,均P>0.05）。肺MALT淋巴瘤患者的CT值高于炎症型NSCLC患者[(45.4±10.5） HU对（21.6±50.1） HU],且差异有统计学意义（t=30.89,P<0.001）;肺MALT淋巴瘤患者的SUV_max和SUV_peak较炎症型NSCLC患者低[（5.71±2.10）对（9.89±4.53）、（4.48±2.31）对（7.46±4.44）],且差异均有统计学意义（t=?4.58、?3.23,均P<0.01）。 结论 18F-FDG PET/CT对于肺MALT淋巴瘤和炎症型NSCLC的鉴别诊断具有重要的价值,其中SUV_max、SUV_peak、脾脏代谢情况以及CT图像中的病变形态、病变位置、CT值等可作为参考指标。     

Lymphadenopathy by Scrub Typhus Mimicking Metastasis on FDG PET/CT in a Patient with a History of Breast Cancer

We report the case of a 60-year-old woman with left-sided breast cancer who showed lymphadenopathy mimicking metastatic lesions. She underwent surveillance ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) after treatment. PET/CT demonstrated multiple lymphadenopathies with increased FDG uptake, most notably in the right axilla. She had an eschar on the right axillary area, and her serologic test was positive for anti-Orientia tsutsugamushi IgM antibody. Ten months after the treatment, follow-up FDG PET/CT and ultrasonography showed improvement in generalized lymphadenopathy.