5年間経過をみたⅡa＋Ⅱc型大腸癌の1例

A Five Year Follow up Case of Type Ⅱa+Ⅱc Colonic Cancer

要旨　患者は64歳，男性．下腹部痛のため注腸X線検査を施行し，下行結腸中部に径5mmの中心陥凹を疑わせる隆起性病変を認めた．内視鏡検査でも中心陥凹をみる平盤状隆起を確認し，生検したところ診断は中等度異型の腺腫とされた．注腸検査，内視鏡検査で経過をみていたところ，隆起も中心陥凹も，共に著しく大きくなり，ひだ集中も著明になったので，浸潤癌を強く疑い，下行結腸切除を行った．切除標本では，粘膜ひだ集中を伴うⅡa＋Ⅱc病変であり，組織学的には，腺腫成分を認めないsmに中等度浸潤する高分化腺癌であった．また，生検組織を詳細に見直すと高度異型腺腫（境界領域病変）と考えられ，異型の極めて低い病変が短期間に粘膜下浸潤を来したと考えられた．

　A 64-year-old male complaining of lower abdominal pain visited our hospital at his age of 59. Barium enema and endoscopic examination revealed an elevated lesion with a central depression, 5 mm in size, in the middescending colon. A biopsy specimen obtained from this lesion was diagnosed as adenoma with moderate atypia. We followed the lesion bybarium enemas and endoscopic examinations based on its pathological diagnosis.

　Follow-up examinations showed the size of the lesion had been increased, and the central depression and converging folds had developed prominently. We made a diagnosis of carcinoma with submucosal invasion, and descending colectomy was performed.

　The resected specimen of the colon was macroscopically type Ⅱa+Ⅱc. Histological examination showed well differentiated adenocarcinoma with submucosal invasion (sm₂). Adenomatous component was not ldentified in the resected specimen. Reexamination of the initial biopsy specimen by serial sections revealed adenoma with severe atypia or carcinoma with low grade atypic. This is a interesting case showing carcinoma with low grade atypia invading to the submucosal layer in a short period.