術後34年で再発が確認された甲状腺癌多発肺転移の一例

A Case of Papillary Thyroid Carcinoma that Recurrence was Found by Multiple Lung Metastases in Postoperative 34 Years

要旨　甲状腺癌の大多数を占める甲状腺乳頭癌は，細胞増殖速度が非常に緩慢であり予後が良好な癌種である．今回われわれは，術後34年経過後に，多発肺転移で発見された甲状腺乳頭癌の1例を経験した．症例は63歳男性．1971年に甲状腺癌に対し，甲状腺全摘術およびコバルト外照射による治療歴がある．2005年10月に肺野のびまん性粒状影を指摘され，当科紹介受診となった．胸部X線および胸部CT画像にて両肺びまん性に粒状～小結節影を認め，血液検査ではサイログロブリンが高値を示した．¹³¹Iシンチグラフィでは両側肺へのびまん性集積を示し，経気管支肺生検にて濾胞形成を伴い乳頭状に増殖する腺癌の所見が得られた．術後，34年経過後，肺転移で発見された甲状腺癌の再発と診断した．甲状腺乳頭癌は術後長期間経過後に再発を認める場合があり，長期にわたって慎重な経過観察を要すると考えられた．

　Thyroid papillary carcinoma is the most common type of thyroid cancer. Its cell-growth speed is slow, and patients with thyroid papillary carcinoma have better prognoses than those with other cancers. We encountered a patient in whom papillary thyroid carcinoma recurred as multiple lung metastases 34 years after the operation.

　A 64-year-old man had a history of radical thyroidectomy and internal radiation therapy with cobalt for thyroid cancer. In October 2005, he presented at our hospital because of diffuse granular shadow in his lung on radiography. Chest radiography and computed tomography showed diffuse granular and small nodular shadow in both lungs, but blood test did not show a decrease in thyroid hormone in spite of the thyroid hormone agent self-stop. Thyroid scintigraphy showed a high radioiodine uptake in both lungs, and transbronchial lung biopsy showed adenocarcinoma with papillary growth and follicular formation. The patient was diagnosed with recurrence of the thyroid cancer with lung metastasis 34 years after the operation.

　Thyroid papillary carcinoma may recur even after a long time after thyroidectomy. Therefore, we recommend cautious long-term observation in these patients.