A Rare Case of Differentiated Thyroid Carcinoma with Liver Metastases.

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.