Increased participation in habitual physical activity is associated with higher BAT activity. Moreover, individuals with normal BMI demonstrate higher BAT activity compared to overweight and obese individuals. Finally, age is inversely linked with BAT activity, while women demonstrate higher BAT activity than men.

18F-fluorothymidine (18F-FLT) is a radiolabeled thymidine analog that has been reported to help monitor tumor proliferation and has been studied in primary brain tumors; however, knowledge about 18F-FLT positron emission tomography/computed tomography (PET/CT) in metastatic brain lesions is limited. The purpose of this study is to evaluate the performance of 18F-FLT-PET/CT in metastatic brain lesions. A total of 20 PET/CT examinations (33 lesions) were included in the study. Semiquantitative analysis was performed: standard uptake value (SUV) with the utilization of SUVmax, tumor-to-background ratio (T/B), SUVpeak, SUV1cm3, SUV0.5cm3, SUV50%, SUV75%, PV50% (volume × SUV50%), and PV75% (volume × SUV75%) were calculated. Sensitivity, specificity, and accuracy for each parameter were calculated. Optimal cutoff values for each parameter were obtained. Using a receiver operating characteristic (ROC) curve analysis, the optimal cutoff values of SUVmax, T/B, and SUVpeak for discriminating active from non-active lesions were found to be 0.615, 4.21, and 0.425, respectively. In an ROC curve analysis, the area under the curve (AUC) is higher for SUVmax (p-value 0.017) compared to the rest of the parameters, while using optimal cutoff T/B shows the highest sensitivity and accuracy. PVs (proliferation × volumes) did not show any significance in discriminating positive from negative lesions. 18F-FLT-PET/CT can detect active metastatic brain lesions and may be used as a complementary tool. Further investigation should be performed.

Summary Large-cell neuroendocrine carcinoma (LCNEC) is a rare neuroendocrine prostatic malignancy. It usually arises after androgen deprivation therapy (ADT), while de novo cases are even more infrequent, with only six cases described. The patient was a 78-year-old man with no history of ADT who presented with cervical lymphadenopathy. Diagnostic approaches included PET/CT, MRI, CT scans, ultrasonography, biopsies, and cytological and immunohistochemical evaluations. Results showed a poorly differentiated carcinoma in the thyroid gland accompanied by cervical lymph node enlargement. Thyroid surgery revealed LCNEC metastasis to the thyroid gland. Additional metastases were identified in both the adrenal glands. Despite appropriate treatment, the patient died of the disease. De novo LCNEC of the prostate is a rare, highly aggressive tumor with a poor prognosis. It is resistant to most therapeutic agents, has a high metastatic potential, and is usually diagnosed at an advanced stage. Further studies are required to characterize this tumor. Learning points De novo LCNECs of the prostate gland can metastasize almost anywhere in the body, including the thyroid and adrenal glands. LCNECs of the prostate are usually associated with androgen-depriving therapy, but de novo cases are also notable and should be accounted for. Further studies are required to fully understand and treat LCNECs more effectively.

The contribution of positron emission tomography/computed tomography (PET/CT) with 18F-fludeoxyglucose (FDG) in evaluating ovarian cancer recurrence even after a prolonged disease-free interval, and in therapy response is well-described. Calcifications observed in CT, although usually attributed to benign conditions, may actually represent active disease. Such an example of calcified formations is psammoma bodies. We present a case of 56-y. o. patient with ovarian cancer relapse at the supraclavicular area 18 years after complete response and disease-free interval. The patient received chemotherapy and underwent 18F-FDG-PET/CT for the evaluation of treatment response. Both CT corrected and uncorrected PET images showed hypermetabolism in the massively calcified lymph nodes in the neck, mediastinum, axilla and abdomen, indicative of active residual disease.

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Background Large Cell Neuroendocrine Carcinoma (LCNEC) is the rarest neuroendocrine prostatic malignancy. It usually arises after androgen-deprivation therapy (ADT), while de novo cases are even more infrequent with only 6 cases described to date. Case presentation A 78-year-old man with no history of ADT presented with cervical lymphadenopathy. Diagnostic approach included PET/CT, MRI, and CT scans, U/S, biopsies, cytological and immunohistochemical evaluations. CT revealed a non-enriching region on the right lobe of the thyroid gland. An 18F-FDG PET-CT found increased uptake in the thyroid gland and both adrenal glands. Neck ultrasound identified a right thyroid lobe nodule. A fine needle aspiration of the nodule was performed and cytology was consistent with poorly differentiated carcinoma. A total thyroidectomy with central and bilateral lymph node dissection was performed and the pathology report diagnosed a LCNEC metastatic to the thyroid gland. Additional metastases were identified in both adrenal glands. Despite appropriate treatment, the patient succumbed to his disease. Summary We report the first patient with a de novo purely prostatic LCNEC, metastasizing to the thyroid and the adrenal glands. Conclusions De novo LCNECs of the prostate are very rare, highly aggressive tumors with poor prognosis. They are resistant to most therapeutic agents, have high metastatic potential and are usually diagnosed at an advanced stage. Further studies are needed to characterize these tumors. Presentation: Saturday, June 11, 2022 1:00 p.m. - 3:00 p.m., Saturday, June 11, 2022 1:24 p.m. - 1:29 p.m.

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