放射線照射後のS状結腸に認められた極めて高分化な大腸癌の1例

Well Differentiated Adenocarcinoma of the Sigmoid Colon Resembling Colitis Cystica Profunda Resected 23 Years after Pelvic Irradiation, Report of a Case

要旨　患者は61歳，女性．1964年に子宮頸癌根治手術と術後放射線照射を受けた．1984年にS状結腸狭窄を指摘され，X線，内視鏡検査，生検で放射線大腸炎と診断された．1987年に狭窄部生検で癌と診断され，S状結腸切除術を受けた．切除標本では，狭窄部中央に陥凹があり，陥凹肛門側には細胞異型が高度な小さい高分化腺癌が存在した．陥凹の大部分では，粘液を産生する異型に乏しい細胞からなる腺管が，腺管内粘液貯溜や筋層内粘液塊形成を伴い粘膜下層に至るまで侵入しており，colitis cystica profunda（CCP）に類似していた．しかし，上皮の構造異型と破壊性増殖と脈管侵襲を呈することから，やはり高分化腺癌と診断した．周囲には軽度のCCPを伴う典型的晩期放射線性大腸炎が認められた．

　Sigmoid colon stricture developed in a 58-year-old female, 20 years after radiation therapy for uterine cervical cancer. Sigmoidectomy was performed 3 years later, since biopsy from the stenotic lesion of the colon revealed adenocarcinoma.

　Histological examination revealed a small carcinoma on the anal side of the stenosis. In addition, transmural invasion of the mucin-producing epithelium with formation of mucous cysts in the colonic wall was noted at the site of marked stenosis. Although cellular atypia of the invading glands was mild, structural atypia, destructive growth and presence of vascular permeation were useful in differentiating adenocarcinoma from radiation-induced colitis cystica profunda. Typical features of late radiation injury with mild radiation-induced colitis cystica profunda were observed around this well differentiated adenocarcinoma.