乳癌からの転移性胃癌の1例

Metastatic Gastric Cancer from the Breast, Report of a Case

要旨　患者は胃部不快感を訴えて来院した57歳，女性．1年9か月前に乳癌の手術を受けている．胃X線所見では胃体中部後壁に多発する不整陥凹と，その周辺粘膜ひだの肥厚した所見があり，表面に不整形陥凹のある小隆起が胃体上部後壁，胃角後壁大彎寄りにも認められた．内視鏡所見では表面に発赤顆粒と浅い陥凹のある扁平隆起が多発して認められた．これらの所見はメラノーマの胃への転移時にみられる“bull's eye sign”と似ているため以前の乳癌の手術を思い起こし乳癌の胃への転移を強く疑った．胃生検標本にも乳癌の細胞とよく似た癌細胞が認められた．他の部位に転移巣を認めなかったので胃全摘術を施行した．切除胃肉眼標本では胃体中部後壁にクラーテルがあり，その周囲の粘膜ひだは腫瘤状に隆起していた．また，表面に小不整形陥凹のある小隆起性病変が多発していた．病理組織標本では腫瘍細胞が粘膜下層に腫瘤状に見られ，その上に浅い潰瘍形成の見られる部位と固有筋層より漿膜面に腫瘍細胞がびまん性に浸潤している部分が見られた．腫瘍細胞はエオジン淡染性の，異型の目立つ癌細胞で，その中にはPAS陽性のintracytoplasmic luminaを有する癌細胞もあり，これらの腫瘍細胞は原発巣と考えられる乳癌とよく似ていた．以上の所見から，これらの胃病変は乳癌の転移によるものと診断された．文献的にみると剖検例の検討では乳癌の胃への転移はまれではない．乳癌からの転移性胃癌のX線所見はlinitis plastica型が多く，乳癌手術患者でlinitis plastica型胃癌を発見したときは乳癌からの転移も考慮する必要がある．

　A 57-year-old woman was admitted to our hospital because of epigastric pain. She had a history of breast cancer surgically removed one year and nine months prior to the admission.

　Physical and laboratory examinations revealed no abnormalities. Radiological study of the stomach showed irregular-shaped barium flecks surrounded by coarse mucosal folds and multiple polypoid lesions with small barium fleck. These findings were similar to the “bull's eye sign” usually seen in cases of gastric metastasis of malignant melanoma. Endoscopic examination showed multiple flat masses of various sizes, with shallow depression on them. Biopsy specimens obtained from these lesions contained tumor cells identical to the breast cancer cells previously obtained. Further investigations were negative for other metastatic lesions. Total gastrectomy was performed.

　Examination of the resected specimen showed large crater with tumorously engorged mucosal folds in the posterior wall of the middle portion of the gastric body and multiple small polypoid lesions with the small depression as previously seen. Histological examination of the cross sections showed the tumor mass with shallow ulceration, the submucosal layer with expansive growth of tumor cells and the proper muscle layer through the serosa being diffusely infiltrated by tumor cells. These tumor cells were shown to have characteristics identical to the breast cancer. These findings clearly demonstrated that the gastric cancer resulted from the previously treated breast cancer.

　Review of literatures on autopsy cases indicated the unexpectedly higher incidence of gastric metastasis from breast cancer than generally believed. Radiologically, those metastatic lesions presented as linitis plastics type. Thus, when encountered with the linitis plastics type gastric cancer in the patient with previous history of breast cancer, we should always consider a possibility of gastric metastasis from breast cancer.