石川 祐子¹, 池田 克実², 木下 優佳¹, 西澤 輝彦¹, 中通 由美¹, 横田 重樹¹, 上川 禎則³, 福島 裕子⁴, 井上 健⁴, 小川 佳成²

Yuko ISHIKAWA¹, Katsumi IKEDA², Yuka KINOSHITA¹, Teruhiko NISHIZAWA¹, Yumi NAKADORI¹, Shigeki YOKOTA¹, Sadanori KAMIKAWA³, Hiroko FUKUSHIMA⁴, Takeshi INOUE⁴, Yoshinari OGAWA²

¹大阪市立総合医療センター中央臨床検査部, ²大阪市立総合医療センター乳腺外科, ³大阪市立総合医療センター泌尿器科, ⁴大阪市立総合医療センター病理部

¹Department of Central Clinical Laboratory, Osaka City General Hospital, ²Department of Breast Surgical Oncology, Osaka City General Hospital, ³Department of Urology, Osaka City General Hospital, ⁴Department of Pathology, Osaka City General Hospital

キーワード : metastatic breast cancer, male breast cancer, renal cell carcinoma

症例は75歳，男性で，2008年に左腎細胞癌（T1bN0M0）で左腎摘除術を受けている．病理診断はrenal cell carcinoma（clear cell carcinoma）であった．術後3年目のfollow up CTで，左乳房内に径7mmの高濃度結節を認めた．さらに，半年後のCTでは径13mmと増大傾向を認めた．USは左乳房CD領域に境界明瞭で，内部血流の豊富な低エコー腫瘤を認め，針生検で腎癌と類似した組織像を認め，renal cell carcinomaの乳腺転移と診断した．男性の原発性乳癌は全乳癌の1％程度であるが，転移性乳癌はさらに稀少である．また，転移性乳癌の原発巣は本邦では対側乳癌，胃癌，白血病，悪性リンパ腫の順に多いが，腎癌からの乳腺転移はほとんど報告例をみない．今回我々は，男性で腎癌の乳腺転移と診断した非常にまれな症例を経験したので，若干の文献的考察を加えて報告する．

The patient is a 75-year-old man who underwent nephrectomy for renal cell carcinoma (clear cell carcinoma) in 2008. Follow-up enhanced computed tomography in 2011 showed a 7mm diameter tumor in the left breast, and the tumor subsequently increased to 13mm in diameter after six months. We suspected that the breast tumor was a primary or metastatic carcinoma from renal cancer. Ultrasonography demonstrated the features of the tumor, which were a well-circumscribed hypoechoic mass with abundant vascularity. The findings of core needle biopsy suggested a metastatic breast tumor from clear cell carcinoma. Male breast cancer is rare, accounting for less than 1% of all breast cancer cases. Furthermore, metastatic male breast cancer is an extremely unusual disease. It is known that the primary tumors of metastatic breast cancer are contralateral breast cancer, gastric cancer, leukemia, and malignant lymphoma. However, renal cell carcinoma has been rarely reported. To our knowledge, this is a first report in Japan related to metastatic male breast cancer from renal cell carcinoma.