癌性胸膜炎を契機に発見された甲状腺濾胞型乳頭癌による全身転移の症例

Follicular Variant of Thyroid Papillary Carcinoma with General Metastases including Pleuritis Carcinomatosa:a case report

要旨　症例は82歳男性．脳内出血，高血圧，心房細動，深部静脈血栓症の既往がある．右胸水精査のため入院した．胸水細胞診で腺癌細胞を認め，CT・MRI検査で多発肺転移・骨転移・副腎転移，甲状腺右葉に石灰化を有する腫瘍を認めた．甲状腺穿刺吸引細胞診で癌細胞を検出し，甲状腺癌に伴う全身転移と診断した．高齢，Performance Status不良により，緩和治療の方針となり，第42病日，癌性胸膜炎による呼吸不全で死亡した．病理解剖を行い，病理組織所見で甲状腺腫瘍は濾胞型乳頭癌と判明した．また，癌細胞の脈管・リンパ管浸潤が証明され，甲状腺癌が血行性・リンパ行性に全身転移を来したと考えられた．濾胞型乳頭癌は高率にリンパ節転移を来すが，血行性転移は稀である．また，乳頭癌が癌性胸膜炎を発症することも稀である．本症例は，濾胞型乳頭癌が血行性・リンパ行性転移を来し，癌性胸膜炎を発症した稀なケースであると考えられた．

　An 82-year-old man with a history of cerebral hemorrhage, hypertension, atrial fibrillation, and deep venous thrombosis was admitted to our institution for the evaluation of right pleural effusion. Cytodiagnosis revealed the presence of an adenocarcinoma, whereas computed tomography and magnetic resonance imaging indicated the presence of multiple lung and bone metastases, adrenal metastasis, and a right thyroid tumor with calcification. Moreover, fine-needle aspiration biopsy of the thyroid indicated the presence of malignant cells, leading to a diagnosis of thyroid carcinoma with general metastases including malignant pleural effusion. Because of the patient's advanced age and poor performance status, he was provided with the best supportive care possible;however, he died of respiratory failure due to malignant pleural effusion on day 42 after admission. Subsequently, an autopsy was performed with his family's consent. Pathological examination indicated the presence of follicular variant of papillary thyroid carcinoma and showed the presence of cancer cells in lymph and vascular vessels. Therefore, in this case, thyroid cancer cells might have spread systemically through lymphogenous and hematogenous routes. Usually, follicular variant of papillary thyroid carcinoma metastasizes via the lymphogenous route and rarely metastasizes via the hematogenous route. Furthermore, papillary thyroid carcinoma is rarely complicated with malignant pleural effusion. Thus, this case presentation is atypical and requires appropriate consideration to facilitate accurate and prompt diagnosis in future patients.