竹内 直人¹, 井口 研子², 澤 文¹, 松尾 知平¹, 岡崎 舞¹, 橋本 幸枝², 坂東 裕子², 近藤 譲³, 原 尚人²

Naoto TAKEUCHI¹, Akiko IGUCHI-MANAKA², Aya SAWA¹, Tomohei MATSUO¹, Mai OKAZAKI¹, Sachie HASHIMOTO², Hiroko BANDO², Yuzuru KONDO³, Hisato HARA²

¹筑波大学附属病院乳腺甲状腺内分泌外科, ²筑波大学医学医療系乳腺内分泌外科, ³独立行政法人国立病院機構霞ヶ浦医療センター病理診断科

¹Department of Breast, Thyroid and Endocrine Surgery, University of Tsukuba Hospital, ²Department of Breast and Endocrine Surgery, Institute of Medicine, University of Tsukuba, ³Department of Pathology, Kasumigaura Medical Center

キーワード : breast metastasis, thyroid carcinoma

症例は50代女性．甲状腺乳頭癌の診断で当院当科へ紹介受診となり，全身検索目的のPET-CTでFDG集積を伴う右乳房腫瘤ならびに多臓器転移を認め，乳癌との重複癌が疑われた．視触診で右乳頭直下に1cmの弾性硬腫瘤を触知，乳房超音波検査で右乳房中央部領域深部に長径10mm，境界明瞭平滑，血流豊富な楕円形低エコー腫瘤を認めた．同病変に対して針生検を施行し，組織型は評価困難であったが，免疫組織化学的検討により，甲状腺乳頭癌乳房転移と診断した．待機的に手術を予定していたが，急激な病勢の進行を認め，緊急で甲状腺全摘術＋気管切開術を施行した．術後病理で甲状腺腫瘍は甲状腺未分化癌と診断され，また右乳房腫瘤は最終的な病理診断には至らなかったが，急激な転帰ならびに画像上転移性腫瘍に矛盾しない所見があったことからも，甲状腺未分化癌乳房転移の診断が適切と考えられた．他臓器悪性腫瘍の乳房転移は非常に稀であり，また本症例では乳房腫瘤の確定診断に苦慮した．転移性乳房腫瘍の画像的特徴に加えて，原発腫瘍の画像的特徴も考慮し，総合的に判断することが肝要と考える．

The patient was a woman in her 50s. She was referred to our department with a diagnosis of papillary thyroid carcinoma. PET-CT performed for systemic search revealed a right breast mass with FDG accumulation and multi-organ metastasis, which was suspected to be an overlapping cancer with breast cancer. On palpation, a 1-cm-sized hard elastic mass was palpated just below the right nipple. Breast ultrasonography revealed an oval hypoechoic mass with a 10-mm diameter, smooth borders, and abundant blood flow at 6:00C section depth in the right breast. A needle biopsy was performed, and although the histological type was difficult to evaluate, a diagnosis of breast metastasis from papillary thyroid carcinoma was made based on immunohistochemical examination. Surgery was scheduled, but rapid progression of the disease was observed, and a total thyroidectomy and tracheostomy were performed urgently. Postoperative pathology diagnosed the thyroid tumor as anaplastic thyroid carcinoma, and although a final pathological diagnosis of the right breast mass was not reached, the diagnosis of breast metastasis from anaplastic thyroid carcinoma was considered appropriate given the rapid outcome and the findings consistent with a metastatic tumor on imaging. Breast metastasis from malignant tumors of other organs is extremely rare, and in this case, the definitive diagnosis of a breast mass was difficult to make. In addition to the imaging features of a metastatic breast tumor, it is important to consider the imaging features of the primary tumor and make a comprehensive judgment.