Objectives: Endometrial cancer (EC) is the most common gynecological malignancy. The 18 fluorine-fluorodeoxyglucose ( 18 F-FDG) positron emission tomography/computed tomography (PET/CT) is used for initial staging, evaluating treatment response, and detecting recurrence. This study aimed to investigate the diagnostic value of preoperative PET/CT in EC staging and determine the volumetric PET parameters that are accurate predictors of histopathological tumor characteristics. Methods: Preoperative PET/CT data of 66 patients with EC were retrospectively analyzed. Patients were divided into low and high-risk groups according to the European Society for Medical Oncology criteria. The maximum standardized uptake value (SUV max ), SUV mean , metabolic tumor volume (MTV), and total lesion glycolysis (TLG) of the primary lesion and pathological lymph nodes were noted. The International Federation of Gynecology and Obstetrics (FIGO) classifications, histopathology, the depth of myometrial invasion (MI), lymph node metastasis (LNM), cervical stromal invasion (CSI), and tumor sizes were noted. Results: The SUV max , TLG, and MTV values of high and low-risk groups were significantly different. TLG was the most useful parameter in differentiating risk groups. PET/CT had 90% sensitivity, 96.3% specificity, 81.8% positive predictive value, 98.1% negative predictive value, and 95.45% accuracy in assessing LNM. MTV and TLG values in patients with non-endometrioid pathology were higher than those with endometrioid. The SUV max , MTV, and TLG of patients with deep MI were higher than those with superficial MI. TLG values of patients with CSI were higher than those without CSI. Patients with LNM had higher MTV and TLG values than those without LNM. A significant difference was found in TLG, MTV, and SUV max values between patients with FIGO stage I-II and patients with FIGO stage III and above. Conclusion: SUV and volumetric parameters obtained from PET/CT, especially TLG, are strong predictors of tumor characteristics, such as MI and CSI, FIGO stages, and LNM, and are useful in noninvasively defining the risk groups in the preoperative period.

Papillary thyroid carcinoma (PTC) is the most frequent type of differentiated thyroid cancers (DTCs) and commonly metastasizes to regional lymph nodes. Distant metastases of DTC typically occur in the lungs and bones. Liver metastases of DTC are very rare and difficult to diagnose. We present a case of a 52-year-old woman who had a previous history of PTC treated by total thyroidectomy and lymph node dissection. The patient received two radioactive iodine-131 (I-131) treatments. The second postradioiodine therapy whole-body scan (WBS) revealed intense iodine uptake in the neck region and in the lungs. After 2 months, during the follow-up period, increase in serum thyroglobulin (Tg) level was detected. Positron-emission tomography–computed tomography (PET-CT) with 18F-fluorodeoxyglucose (FDG) revealed increased FDG uptake in the mass lesion that invaded the muscles in the neck area, lung, bone, and liver. The uptake in liver was interpreted as suspicion of malignancy. The trucut biopsy of the liver masses demonstrated metastases of the thyroid carcinoma with the immunohistochemical thyroid transcription factor-1 and PAX8 positivity observed in these tumor cells. In DTC patients with progressive rapid rise of Tg level, the diagnostic value of I-131 WBS will decrease as the differentiation of the tumor decreases. The combined use of I-131 WBS and FDG PET-CT as diagnostic modalities in these patients will be important in treatment planning in detecting locoregional or distant metastases, especially in patients with negative diagnostic I-131 WBS.