寺元 佳奈¹, 土井 康郎², 山本 加代¹, 松川 要¹, 祝原 久香¹, 元島 留美¹, 高田 登³, 吉仲 一郎³, 原田 和則³

Kana TERAMOTO¹, Yasuro DOI², Kayo YAMAMOTO¹, Kaname MATSUKAWA¹, Hisaka IWAIHARA¹, Rumi MOTOSHIMA¹, Noboru TAKATA³, Ichiro YOSHINAKA³, Kazunori HARADA³

¹天草地域医療センター検査部, ²土井外科消化器内科医院, ³天草地域医療センター外科

¹Department of Clinical Laboratory,Amakusa Medical Center, ²Doi Surgical Gastroenterology Clinic, ³Department of Surgery, Amakusa Medical Center

キーワード : periductal stromal sarcoma, breast, fibroepithelial tumors, nonepithelial tumors, spindle cell tumor

症例は63歳女性．2012年，右乳房の発赤を伴う硬結を主訴に受診．葉状腫瘍と診断され腫瘍摘出術施行．術後病理結果は乳腺症であり経過観察．2年後，切除部位に同症状を認め再検査．超音波検査で右乳房A領域に広がり5 cmの地図状低エコー域を認めた．皮下脂肪層内にも低エコーが進展し，浸潤による限局性皮膚肥厚が示唆された．パワードプラで豊富な血流信号を認めた．2012年と異なる所見は，皮膚から大胸筋までの厚みが増したこと，病変が拡大し，境界が不明瞭化していることであり，臨床症状も加味すると炎症性乳癌も否定できない画像所見であった．右乳房切除術施行．病理所見では紡錘形腫瘍細胞が正常腺管の周囲に浸潤性に増殖する病理組織像を認めた．紡錘形腫瘍細胞は免疫組織化学染色でビメンチン，CD34に陽性を示し，periductal stromal sarcoma（PSS）と診断．初発時の切片を再評価すると，再発腫瘍と同様の腫瘍成分を認めた．PSSは報告例も少なく，臨床および画像上特徴的な所見も乏しく診断が困難とされる．初回手術では確定診断に至らず，局所再発をきたしたPSSの1例を経験したので，超音波画像所見を中心に報告する．

The case involved a 63-year-old female who had complained of a hard reddish lump in the right breast. Although the lump initially appeared to be a phyllodes tumor, histopathology after initial surgery indicated mastopathy as a likely diagnosis. Two years later, regrowth of the lump at the same location prompted revaluation. Ultrasound scan (US) revealed the following features: a) an irregular low-signal lesion with a diameter of 5 cm in the right A region extending toward the hypertrophic epidermis, b) marked increase in blood flow on power Doppler, c) increased thickness between the skin and underlying pectoralis major, and d) irregular and unclear margin of low-echoic lesion. Based on those findings along with clinical symptoms, advanced stage of inflammatory breast cancer was suspected, and a second surgery was performed. Histopathology revealed infiltration of atypical spindle cells around normal mammary ducts, but it did not show the architecture of a phyllodes tumor. The atypical spindle cells were positive for vimentin and CD34 and negative for hormone receptors according to immunohistochemistry. These were consistent with the characteristics of periductal stromal sarcoma. The section diagnosed as mastopathy 2 years previously was re-evaluated by pathologists, and components of stromal sarcoma were found in the section. Stromal sarcoma is rare for the breast region and usually lacks specific features, which may make the precise diagnosis quite difficult. In our case, the following factors contributed to the misleading diagnosis: invasive growth without forming a firm mass, less prominent nuclear pleomorphism and low proliferation index, and inconsistent US features compared to the previous report, etc. The generally poor prognosis of this tumor should demand long-term observation even though no recurrence has been found after the second surgery.