Ga-PSMA-HBED-CC PET/CT is a potentially useful imaging modality in patients of mDTC with most (70%) of PSMA expressing metastasis being localized to the bones. PSMA PET/CT could be useful for identifying patients with limited therapeutic options (eg, TENIS) who might benefit from PSMA-targeted radionuclide therapy.

Purpose of the Report Prostate-specific membrane antigen (PSMA) is a member of superfamily of zinc-dependent exopeptidases that is robustly expressed in prostate cancer cells and nonprostatic solid tumor neovasculature including microvessels of thyroid tumors. Its expression in differentiated thyroid cancer (DTC) has been confirmed in many recent studies, but systematic studies exploring PSMA expression in patients with DTC with thyroglobulin elevation and negative iodine scintigraphy (TENIS) are lacking. The aim of the present study was to evaluate the role of PSMA scan in TENIS patients with DTC. Methods Nine consecutive patients with DTC with proven TENIS syndrome (6 men and 3 women with age range 29–68 years and mean age of 48 years) underwent 18F-FDG PET/CT as per the institution protocol. Thereafter, they were subjected to 68Ga-PSMA-HBED-CC PET/CT as per the institution protocol within a week of FDG PET imaging. Prostate-specific membrane antigen expression (SUVmax) in the lesions was compared with 18F-FDG PET and CT scan findings. Results In 5 of 9 patients with TENIS, the metastatic lesions showed PSMA expression. A total of 14 lesions were seen on the CT scan. Prostate-specific membrane antigen PET detected 9 of 14 lesions (64.28%) (SUVmax ranging from 10.1 to 45.67; median SUVmax of 16.31), whereas FDG PET was positive in 11 of 14 lesions (78.57%). The lesions that showed PSMA uptake was localized to bones (5 of 9) and lungs (4 of 9). Two lesions that were localized to iliac crest and acetabulum were missed on FDG PET but were seen on CT and PSMA PET scan. Conclusions The results of this pilot study indicate that 68Ga-HBED-CC-PSMA PET/CT demonstrates PSMA expression in TENIS patients with lesions being localized to the bones and lungs. 68Ga-PSMA PET/CT could be useful for the identification of TENIS patients who might benefit from PSMA-targeted radionuclide therapy.

Tumor thrombus is a rare complication of many solid tumors. We present a case of renal cell carcinoma whose baseline contrast-enhanced computerized tomography (CT) revealed an heterogeneously enhancing mass in the upper half of right kidney with tumor thrombus in the right renal vein extending to suprarenal inferior vena cava (IVC), crossing the cavoatrial junction and reaching up to the right atrium (Grade IV). Fluorine-18 fluorodeoxyglucose (18F-FDG) positron emission tomography (PET)/CT imaging revealed large irregular right renal mass, hypermetabolic tumor thrombus extending from the right renal vein to suprarenal IVC reaching up to the right atrium. There was no FDG uptake noted in the infrarenal IVC and bilateral iliofemoral venous thrombi. Thus, 18F-FDG PET/CT was not only helpful in the staging, but was also helpful in differentiating tumor thrombus from bland thrombus in our patient.

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