Ⅱc型印環細胞癌を伴った異時性多発大腸癌の1例

Colorectal Multiple Carcinomas Involving Superficial Type (Ⅱc) Signet-ring Cell Carcinoma, Report of a Case

要旨　直腸進行癌術後のサーベイランスで発見された異時性早期横行結腸癌の1例を経験した．本症例は第2癌がⅡc型で組織型が印環細胞癌を主体とすること，第1癌が23歳時，第2癌が26歳時と若年性に発症したこと，microsatellite instability（MSI）の解析では検索した8領域のうち第1癌が5領域，第2癌が6領域と高率に陽性であること，K-ras，p53の変異解析はいずれも野生型であることなどの特徴を有していた．本症例はまれな例ではあるが，その臨床病理学的所見は，多発大腸癌のリスク要因を解明するにあたり示唆に富む症例であると考えられる．

　The colon is an organ in which multiple cancers occurs frequently. Because its early diagnosis is central to its efficient management, identifying the risk factors of colorectal multiple cancers and establishing a surveillance program are essential. However, many clinical and pathologic features of colorectal multiple cancers currently remain unclear. Therefore, we report a case of colorectal multiple cancers that we encountered recently.

　Our patient had undergone an operation for moderately differentiated adenocarcinoma of the rectum when he was 23 years old; signet-ring cell carcinoma showing superficial type (Ⅱc) macroscopically was identified 3 years later in his transverse colon. Although positive for carcinoma, his family history was not consistent with the criteria of HNPCC. Microsatellite instability (MSI) was documented in five of the eight sequences analyzed in the rectal carcinoma and in six of the eight evaluated in the cancer in his transverse colon. Both tumors had wild-type K-ras and p53. This case is an extremely rare example, but, it is thought that the case is suggestive for the elucidation of the risk factor of multiple cancers of the colon. The risk of multiple cancer is increased in patients with MSI-positive tumors. Therefore, prompt and regular screening for these characteristics will facilitate early diagnosis and treatment of multiple cancers of the colon.