長径9mmの直腸pm癌の1例

Rectal Cancer 9 mm in Size with Invasion to the Proper Muscle Layer, Report of a Case

要旨　患者は69歳，女性．血便を主訴とし来院．直腸指診で歯状線から5cmに示指頭大の芯のある可動性のやや乏しい隆起性病変を触知．注腸では直腸下部の長径1.5cmのⅠs型の病変で，側面像で弧状変形および腫瘍への粘膜ひだの集中像を認め，深達度SM′と診断．大腸内視鏡でも粘膜ひだの集中を認めるのが特徴的だった．超音波内視鏡では第4層の肥厚および毛羽立ちを認め，深達度PM₁′と診断．切除標本では9×9mmの中央がやや陥凹したIs型様の病変で，肉眼的に辺縁は健常粘膜をかぶり粘膜下層に深く浸潤し，PM癌と診断．組織学的にはpmの浅層まで癌が浸潤した中分化腺癌で，n₁（＋），ly₂，v₁であった．術前の深達度診断に際して，注腸の側面像だけでなく，粘膜ひだの集中像もpm癌を疑う重要な所見であると考えられた．

　A 69-year-old woman was admitted to our hospital with complaints of bloody stool. On digital examination, the tumor was palpable 5 cm above the dentate line. The tumor was an index finger-tip-sized, elastic hard and poorly movable from the colonic wall. Barium enema and colonoscopic examinations revealed a flat elevated lesion in the lower rectum. It was interesting that the lesion was accompanied by converging folds, although the size of the tumor was less than 10 mm. We diagnosed that this lesion invaded the deep submucosal layer or superficial proper muscle layer. Low anterior resection with lymph node dissection was performed. The resected specimen showed the lesion was type Ⅰs-like and 9 mm in diameter. Histological diagnosis was moderately differentiated adenocarcinoma. Cancer cells infiltrated into the superficial proper muscle layer and metastasized to para-rectal lymph nodes (n₁).

　This case showed an importance of “converging folds” for predicting invasivity. We should diagnose that cancer cells invade at least the proper muscle layer, when we recognize converging folds.