FDG-PETが原発巣の同定に有用であったPTEとPTTMを合併した甲状腺原発低分化型腺癌の1例

A case of poorly differentiated adenocarcinoma of the thyroid gland with PTTM for which FDG-PET was useful for identifying the primary lesion

悪性腫瘍は血液凝固能が亢進し血栓塞栓症を合併する頻度が高く，特に脳梗塞を合併した場合はトルソー症候群と呼ばれている。また腫瘍細胞自体が肺動脈の微小血管を塞栓し肺高血圧や呼吸困難をきたす病態は肺腫瘍血栓性微小血管症（pulmonary tumor thrombotic microangiopathy：PTTM）と呼ばれ，どちらも悪性腫瘍に合併する予後不良の病態である。今回我々は肺血栓塞栓症（pulmonary thromboembolism：PTE）と頸部リンパ節転移で発症した原発不明癌で，FDG-PETがPTTMを伴う甲状腺低分化型腺癌の診断に有用であった1例を経験した。甲状腺癌がPTTMを合併した報告は渉猟した限りでは認めず，文献的考察を加え報告する。

The case was a man in his 40s. The chief complaint is dyspnea. Contrast-enhanced CT showed bilateral pulmonary artery embolus, lower extremity venous thrombosis and swelling of the mediastinum, axilla, and supraclavicular lymph nodes. FDG-PET showed accumulation of lymphadenopathy and pale FDG in both lung fields. Both lobes of the thyroid gland were diffusely swollen, with uneven accumulation of FDG. Poorly differentiated cancer and malignant lymphoma against the background of chronic thyroiditis were suspected. Thyroid puncture proved to be a diagnosis of adenocarcinoma. Pathological autopsy revealed poorly differentiated thyroid adenocarcinoma and PTTM. We report on the findings of FDG-PET in thyroid cancer and PTTM with a review of the literature.