[ 18 F]FDG PET/CT in Primary Angiosarcoma of the Thyroid.

Thyroid angiosarcoma is an extremely rare and aggressive malignancy, comprising <1% of thyroid cancers. We present the case of a 58-year-old man with symptoms of cervical lymphadenopathy, hemoptysis, and dysphagia. [ 18 F]FDG PET/CT revealed a hypermetabolic, centrally necrotic mass in the thyroid, with extensive metastases to the lungs, mediastinal and cervical lymph nodes, as well as the adrenals. Ultrasound-guided fine-needle aspiration identified a spindle-shaped neoplasm, initially suspected as thyroid carcinoma. Histopathologic analysis confirmed poorly differentiated angiosarcoma with strong ERG and partial CD34 positivity, supporting its vascular origin. The rarity and rapid progression of thyroid angiosarcoma highlight the importance of early diagnosis and intensive treatment.