Syphilitic bone destruction on FDG PET/CT

A 35-year-old man underwent PET/CT scan to evaluate suspected osseous metastases from a presumed tumor of unknown origin. PET images demonstrated multiple foci of increased FDG uptake in all extremities, corresponding to the osseous destruction on the concurrent CT images. However, no primary tumor was identified. Instead, the bone lesions were subsequently proven due to syphilis infection.     

False-positive lesions mimicking breast cancer on FDG PET and PET/CT

OBJECTIVE: Incidental (18)F-FDG-avid breast lesions are commonly encountered in patients with cancer who undergo staging PET/CT. This pictorial essay discusses breast lesions that show increased FDG activity, mimicking breast cancer, with biopsy-confirmed benign diagnosis. CONCLUSION: Acute and chronic inflammation, physiologic lactation, and benign breast masses, including silicone granuloma, fat necrosis, fibroadenoma, and postsurgical changes, may show increased FDG uptake on PET/CT. These conditions can often be differentiated from malignancy by correlative imaging, including mammography, sonography, or MRI.     

Incidental colonic focal lesions detected by FDG PET/CT

OBJECTIVE: The aim of this study was to assess the performance of FDG PET/CT for the detection of colonic lesions, especially advanced neoplasms (villous or >10-mm adenomas, carcinomas). Because of 18F FDG accumulation in adenomatous polyps, PET using FDG can detect early premalignant colorectal lesions. MATERIALS AND METHODS: FDG PET/CT studies performed for a 1-year period in 1,716 consecutive patients with various malignant diseases, except colorectal cancer, were retrospectively reviewed. PET images obtained 1 hr after FDG injection and non-contrast CT images used for attenuation correction were fused for analysis. Of 45 patients showing intense focal colonic FDG uptake, 20 patients (with 21 foci) underwent a colonoscopic investigation, and, when necessary, polyp resection. The intensity of FDG uptake was quantified using the standardized uptake value (SUV(max)). RESULTS: The FDG colonic foci were associated with 18 colonoscopic abnormalities in 15 patients, with no colonic abnormality detected in five patients (false-positive [FP] results). Histopathologic findings revealed advanced neoplasms in 13 patients (13 villous adenomas and three carcinomas) and two cases of hyperplastic polyps. A difference in the mean SUV(max) was found between FP and true-positive colonic FDG foci but was not statistically significant (p = 0.14). CONCLUSION: Presence of a focal colonic FDG uptake incidental finding on a PET/CT scan justifies a colonoscopy to detect (pre-)malignant lesions. The fusion of PET and CT images allows an accurate localization of the lesions. PET/CT is a useful tool to differentiate pathologic from physiologic FDG uptake.     

Ipilimumab-induced colitis on FDG PET/CT

A 52-year-old woman with metastatic melanoma was treated with ipilimumab. After 2 cycles of treatment, she developed watery diarrhea, sweats, and chills. An FDG PET/CT study demonstrated new FDG-avid (maximum standardized uptake value 15.6) diffuse colonic wall thickening, suggestive of ipilimumab-induced colitis. The patient was treated with systemic steroids, with subsequent resolution of her symptoms. Based on the response to steroids, the diagnosis of ipilimumab-induced enterocolitis was made. Ipilimumab may cause several immune-mediated toxicities, the most common of which is enterocolitis. Physicians interpreting FDG PET/CT examinations of patients treated with ipilimumab should be aware of these FDG-avid immune-mediated toxicities.     

FDG PET and other imaging modalities in the primary diagnosis of suspicious breast lesions

Mammography is the primary imaging modality for screening of breast cancer and evaluation of breast lesions (T staging). Ultrasonography is an adjunctive tool for mammographically suspicious lesions, in patients with mastopathy and as guidance for reliable histological diagnosis with percutaneous biopsy. Dynamic enhanced magnetic resonance mammography (MRM) has a high sensitivity for the detection of breast cancer, but also a high false positive diagnosis rate. In the literature, MRM is reported to have a sensitivity of 86-96%, a specificity of 64-91%, an accuracy of 79-93%, a positive predictive value (PPV) of 77-92% and a negative predictive value (NPV) of 75-94%. In unclarified cases, metabolic imaging using fluorine-18 fluorodeoxyglucose positron emission tomography (FDG PET) can be performed. In the literature, FDG PET is reported to have a sensitivity of 64-96%, a specificity of 73-100%, an accuracy of 70-97%, a PPV of 81-100% and an NPV of 52-89%. Furthermore, PET or PET/CT using FDG has an important role in the assessment of N and M staging of breast cancer, the prediction of tumour response in patients with locally advanced breast cancer receiving neoadjuvant chemotherapy, and the differentiation of scar and cancer recurrence. Other functional radionuclide-based diagnostic tools, such as scintimammography with sestamibi, peptide scintigraphy or immunoscintigraphy, have a lower accuracy than FDG PET and, therefore, are appropriate only for exceptional indications.     

FDG PET/CT flip flop phenomenon in treated lymphoma of bone

A 47-year-old man with primary large B-cell lymphoma of bone underwent an F-18 fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) scan for staging. The study demonstrated multiple areas of uptake consistent with osseous lymphoma. After multiple cycles of chemotherapy, a follow-up study demonstrated a dramatic flip flop appearance in which the previously noted areas of osseous lymphoma were photopenic and normal marrow appeared to have increased activity. This flip flop appearance could incorrectly suggest lymphomatous infiltration of normal marrow.     

FDG uptake in abdominal mesh implant on FDG PET/CT

A 50-year-old man with peritoneal angiosarcoma underwent total tumor excision along with removal of the total right rectus and medial part of the left rectus muscles 1 year earlier. F-18 fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) was performed for suspected recurrence. In the anterior abdominal wall extensive subcutaneous FDG uptake showing linear hypermetabolic zone on PET slices was noted. The patient had a history of a dual mesh implant, which consists of polypropylene and polyvinylidene fluoride for the reinforcement of the abdominal wall during the operation. PET/CT fusion image demonstrated that the finding was due to the dual mesh implant in the anterior abdominal wall most likely representing a foreign body reaction.     

Dual-time point PET/CT with F-18 FDG for the differentiation of malignant and benign bone lesions

Purpose  The purpose of the present study was to evaluate whether 2-fluoro[fluorine-18]-2-deoxy-d-glucose (F-18 FDG) positron emission tomography (PET) could differentiate malignant and benign bone lesions and whether obtaining delayed F-18 FDG PET images could improve the accuracy of the technique. Methods  In a prospective study, 67 patients with bone lesions detected by computed tomography (CT) or magnetic resonance imaging were included. Whole body PET/CT imaging was performed at 1 h (early) after the F-18 FDG injection and delayed imaging at 2 h post injection was performed only in the abnormal region. Semiquantitative analysis was performed using maximum standardized uptake value (SUV_max), obtained from early and delayed images (SUV_maxE and SUV_maxD, respectively). The retention index (RI) was calculated according to the equation: RI = (SUV_maxD − SUV_maxE) × 100/SUV_maxE. Histopathology of surgical specimens and follow-up data were used as reference criteria. The SUV_maxE and RI were compared between benign and malignant lesions. Results  The final diagnoses revealed 53 malignant bone lesions in 37 patients and 45 benign lesions in 30 patients. There were statistically significant differences in the SUV_maxE between the malignant and benign lesions (P = 0.03). The mean SUV_maxE was 6.8 ± 4.7 for malignant lesions and 4.5 ± 3.3 for benign lesions. However, a considerable overlap in the SUV_maxE was observed between some benign and malignant tumors. With a cutoff value of 2.5 for the SUV_maxE, the sensitivity, specificity, and accuracy were 96.0%, 44.0%, and 72.4%, respectively. The positive predictive value (PPV) and negative predictive value (NPV) were 67.1% and 90.9%, respectively. There were significant differences in the RI between the malignant and benign lesions (P = 0.004). But there was overlap between the two groups. The mean RI was 7 ± 11 for the benign lesions and 18 ± 11 for the malignant lesions. When an RI of 10 was used as the cutoff point, the sensitivity, specificity, and accuracy were 90.6%, 76.0%, and 83.7.0%, respectively. The PPV and NPV were 81.4% and 87.1%, respectively. Conclusions  The results of this study indicate that dual-time point F-18 FDG PET may provide more help in the differentiation of malignant tumors from benign ones.     

CT appearance of bone metastases detected with FDG PET as part of the same PET/CT examination

PURPOSE: To retrospectively evaluate lesion findings at computed tomography (CT) performed as part of a combined positron emission tomography (PET)/CT examination in patients suspected of having metastatic bone lesions-lesions that were detected with fluorine 18 fluorodeoxyglucose (FDG) PET as part of the same examination-and to correlate the CT and FDG PET findings. MATERIALS AND METHODS: This HIPAA-compliant study had institutional review board approval, and the need for patient informed consent was waived. Three hundred fifty-nine consecutive patients (191 male patients, 168 female patients; mean age, 56.9 years; age range, 8-92 years) underwent PET/CT. PET images were first reviewed by nuclear medicine physicians who had no clinical information regarding the presence or absence of bone metastasis by using a five-point grading system (0, a lesion was definitely negative for metastasis; 1, a lesion was probably negative; 2, a lesion was equivocal; 3, a lesion was probably positive; and 4, a lesion was definitely positive). For lesions assigned a grade of 3 or 4 at PET, CT characteristics such as the presence or absence of morphologic changes or accompanying findings (including bone destruction) were assessed by radiologists on the CT images obtained during the same imaging session. RESULTS: One hundred seventy-nine lesions in 55 patients were considered to be probable or definite bone metastases at PET. One hundred thirty-three of these lesions in 33 patients were clinically confirmed to be bone metastases at follow-up and/or histopathologic examination. CT revealed osteolytic changes in 41 (31%) and osteoblastic changes in 21 (16%) of the 133 lesions, but no or nonspecific changes were seen at CT in 49 (37%) and 22 lesions (17%), respectively. Of the 179 lesions suspected at PET, 46 ultimately proved to be nonosseous or false-positive for bone metastasis. Of these 46 lesions, 38 were not located in the bone but in adjacent tissues such as the pleura. CONCLUSION: CT images obtained as part of PET/CT scanning were useful in yielding the precise location of bone lesions and thus helping avoid misdiagnosis of bone metastasis; however, CT revealed morphologic changes in only half of the lesions assigned a grade of 3 or 4 at PET.     

Detection of bone metastases: assessment of integrated FDG PET/CT imaging

PURPOSE: To retrospectively evaluate the positive predictive value (PPV) of fluorine 18 fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) in the identification of malignant bone lesions when the PET and CT findings are discordant and concordant. MATERIALS AND METHODS: The study conformed to HIPAA standards, and the need for informed consent was waived by the institutional review board that approved the study. FDG PET/CT reports of 712 patients were reviewed to identify patients with malignant bone lesions. Fifty-nine patients (30 female and 29 male patients; age range, 10-82 years) with 113 lesions were analyzed. With use of confirmation from histopathologic examination or clinical follow-up, the PPVs of the integrated examination and of the stand-alone CT and PET components of the examination were calculated. The results were stratified according to cancer type, chemotherapy status, and number of bone lesions and were compared by using Fisher exact tests. RESULTS: Of 47 lesions with positive findings at both PET and CT, 46 were malignant and one was benign, for a PPV of 98%. Of 31 lesions with positive findings at PET and negative findings at CT, 19 were malignant and 12 were benign, for a PPV of 61%. Of 35 lesions with negative findings at PET and positive findings at CT, six were malignant and 29 were benign, for a PPV of 17%. Independently, the PPV of all lesions with positive findings at PET was significantly higher than that of all lesions with positive findings at CT. Chemotherapy status for lesions with positive findings at CT and the number of lesions per patient had a statistically significant effect on the PPV of examinations (P = .02 and P < .001, respectively). CONCLUSION: PET/CT has a very high PPV for bone metastases (98%) when the findings at PET and CT are concordant; however, in lesions with discordant PET and CT findings at the integrated examination, PPV is markedly diminished.     

Metastatic eccrine porocarcinoma detected on FDG PET/CT

Eccrine porocarcinoma is an uncommon neoplasm of the sweat gland duct and poses a significant risk of cutaneous, regional lymph node, or visceral metastases. A 62-year-old woman with a history of eccrine porocarcinoma in the left flank area underwent an F-18 FDG PET/CT scan, which revealed increased FDG uptake in left pelvic (SUV 6.34) and left axillary regions (SUV 4.02). Wide excision of left axillary and left pelvic lymph nodes was performed, and histopathologic findings were consistent with eccrine porocarcinoma. PET/CT detects metastases accurately and is helpful in the management of patients with eccrine porocarcinoma.     

Bone infarct-associated sarcoma detected on FDG PET/CT

Secondary sarcomas arising on the background of a bone infarct are extremely uncommon. Based on the knowledge of classic imaging patterns, however, lesions like bone infarcts can be recognized during positron emission tomography/computed tomography studies, which are now being performed increasingly in cancer patients. We demonstrate the detection of this rare entity on positron emission tomography/computed tomography and its correlation on magnetic resonance imaging in a 56-year-old man with asymptomatic multifocal osteonecrosis secondary to steroid treatment for polymyositis.     

Primary Pulmonary Lymphoepithelioma-like Carcinoma on FDG PET/CT

A 69-year-old male smoker was referred to ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography-computed tomography (PET/CT) with the indication of a suspicious solitary pulmonary nodule. FDG PET/CT determined a 2.5?×?2-cm soft-tissue lesion (SUVmax, 16.2) with spiculated margins in the hilum of the right lung. A 1-cm diameter lymphadenopathy on the right hilum with an SUVmax of 3.2 was also determined. Transbronchial biopsy of the right hilar lymphadenopathy did not reveal any malignant features in histopathologic examination, and it was determined to be reactive. The patient underwent a right upper lobe segmentectomy, and the histopathologic evaluation revealed that the tumor was a primary lymphoepithelioma-like carcinoma (LELC) of the lung with negative Epstein-Barr virus (EBV) on in situ hybridization studies. In this case report, we mainly focus on the FDG avidity of this very rare kind of tumor comparatively with previous reports and possible explanations of discordancy in FDG avidity in relation to histopathologic characteristics.