甲状腺乳頭癌原発転移性脳腫瘍に対する治療—自験例5例の症例報告と文献的考察

Treatment of Brain Metastases from Papillary Thyroid Carcinomas:Five Surgical Cases in Our Hospital and a Literature Review

Ⅰ．はじめに

　甲状腺癌の組織型別発生頻度では，乳頭癌92.5%，濾胞癌4.8%，髄様癌1.3%，未分化癌1.4%と，圧倒的に甲状腺乳頭癌の頻度が高い¹⁵⁾．甲状腺乳頭癌の脳転移は0.8〜1.3%^5,11,26)と稀であり，その病態，予後や治療法については定まった見解が得られていない．今回われわれは，甲状腺乳頭癌を原発とする転移性脳腫瘍に対して開頭腫瘍摘出術を施行した5例を経験したので，文献的考察を加えて報告する．

　Papillary thyroid carcinoma is the most common thyroid malignancy and usually has an indolent clinical course with a good prognosis. Brain metastasis from thyroid cancer is very rare, occurring in only 0.8-1.3% of all papillary thyroid carcinomas；therefore, the prognosis and treatment of the metastatic tumor are unclear. We describe 5 cases of brain metastases from papillary thyroid carcinoma treated with surgery between 2013 and 2017. Intracranial tumor resection was performed and brain metastases were pathologically diagnosed as papillary thyroid carcinoma in 2 men and 3 women aged 62-72 years（mean 67 years). The surgical treatment for the thyroid cancer was total thyroidectomy in 3 patients, hemithyroidectomy in 1, and no treatment in 1. The duration from initial diagnosis to brain metastasis was 0-155 months（mean 73.2 months). Two patients also received radioiodine therapy. Three patients had multiple lesions and 2 had single lesions. Four patients also had other metastases. Neuroimaging demonstrated intratumoral hemorrhages in 2 patients. The other 2 patients had intratumoral hemorrhage during the course of the disease. All patients received radiation therapy after surgery for brain metastases. Two patients died, but the other 3 have survived to date. The other 2 patients who had intratumoral hemorrhage during the course of the disease received ¹³¹I radioiodine therapy. It was reported that ¹³¹I radioiodine therapy resulted in collapse of the fragile peritumoral vessels. It is safe to perform head magnetic resonance imaging（MRI）before radioiodine therapy for thyroid cancer. Papillary thyroid carcinomas carry a good prognosis but some brain metastases have a poor prognosis due to the presence of other metastases or the patient's poor general condition. Treatments for patients in good general condition are needed to improve the clinical course and prognosis.