Ⅱc＋Ⅱa型早期大腸癌の1例

Type Ilc＋IIa Early Carcinoma of the Rectum, Report of a Case

要旨　患者は58歳，男性．人間ドックにて便潜血反応陽性であることより大腸精査を受け，直腸にⅡa+Ⅱc型早期癌が発見され，経仙骨式局所切除術が施行された．固定前肉眼所見はⅡc+Ⅱa型を呈し，伸展固定標本ではⅡc型を呈した．病変の大きさは1.4×1.25cm大であった．組織学的には粘膜下層に微少な浸潤を示すⅡc型sm癌であったが，腺管腺癌と腺腫が微妙に混在する病変であり，adenoma-carcinoma sequenceの中でも特異な癌化様式をとったと考えられる1例として報告した．平坦・陥凹型早期大腸癌本邦報告例を集積し，大腸癌組織発生，発育，進展に関する考察を加えた．

　A 58-year-old man, in whom fecal occult blood test was positive at routine check-ups leading to the detection of an early rectal carcinoma by subsequently performed colorectal examination at Kikkoman Hospital, was admitted to Tokyo University Hospital for further examination and treatment.

　Barium enema examination showed a low elevated lesion with central depression in the lower rectum (Fig. 1). The lesion was diagnosed as type Ⅱa＋Ⅱc early carcinoma by colonoscopic observation (Fig. 2). Muscularis mucosae was ultrasonographically almost intact (Fig. 3).

　Trans-sacral excision was performed and the lesion seemed to be type Ⅱc＋Ⅱa early carcinoma at this time (Fig. 4). The fixed specimen, however, revealed an exactly depressed or flat area measured 1.4×1.25cm in size, which might be classified as type Ⅱc (Fig. 5).

　Histologically, the lesion was composed of both carcinomatous and adenomatous glands with the depth of invasion confined to the shallow part of submucosa (Figs. 6 and 7). The lesion was finally classified as type Ⅱc.

　Review of literature published in Japan was made with respect to flat or depressed early carcinoma of the large intestine. Histogenesis and evolution of colorectal carcinoma were discussed with the emphasis on the importance of detecting flat or depressed lesion on routine examinations.