若年発症の異時性多発大腸癌の1例

Metachronous Multiple Colorectal Carcinomas in a Young Patients, Report of a Case

要旨　40歳未満の異時性多発大腸癌の1例を報告した．患者は，30歳時，便秘，黒色便を主訴に来院．横行結腸に2型進行大腸癌を認め，右半結腸切除術施行，以後1年間隔の注腸X線検査で経過観察されていた．35歳時，直腸にIsp病変を指摘され，早期大腸癌（粘膜内癌）の診断のもと内視鏡的切除術を施行された．本症例は若年発症，異時多発，第1癌が右側大腸，第1度近親者が大腸癌であることより，遺伝性非ポリポーシス大腸癌（HNPCC）を強く疑い遺伝子検索を行った．その結果，第1，2癌とも高頻度のマイクロサテライト領域の不安定性とTGF-βRII遺伝子の変異を認めた．以上の結果より本症例がHNPCCである可能性は極めて高いと思われた．本症例は，第1癌発症の時点からHNPCCを疑い，慎重な経過観察をすることにより，第2癌を早期発見し内視鏡的治療しえた症例と思われた．

　A 30-year-old man was initially diagnosed with advanced carcinoma of the transverse colon and underwent right hemicolectomy. Since that time, he has undergone surveillance using barium enema every year. At the age of 35, a subpedunculated polyp of the rectum was pointed out and endoscopic mucosal resection was performed under the diagnosis of intramucosal carcinoma. We suspected this case to be hereditary nonpolyposis colorectal cancer (HNPCC) for the following reasons: the onset was at an early age; the first tumor was located in the proximal colon; metachronous cancer occurred; in the first stage, colorectal cancer was detected. Then we analyzed microsatellite instability and mutation of the TGF-βRII, which revealed both tumors were positive for all genetic markers. From these clinical and genetic results, we confirmed this case as HNPCC. From the first cancer, we dealt with this case as HNPCC and surveillance might lead to early detection of a second cancer.