比較的小さいにもかかわらず粘膜下層で粘液癌形成をみたPG type Ⅰs型sm中等度大腸癌の1例

Small Polypoid-growth Carcinoma (type Ⅰs) with Submucosal Progression of Mucinous Carcinoma, Report of a Case

要旨　患者は44歳，男性．便潜血反応陽性にて精査となる．S状結腸にⅠs型径15mmのポリープを認め，注腸X線所見，大腸内視鏡所見では粘膜下への高度浸潤を疑わせる所見がなく，内視鏡的粘膜切除術を施行．病理所見では粘膜内進展部の部分は管状絨毛腺腫で異型度が弱いが，浸潤先進部に粘液結節を形成する粘液癌がみられ，sm中等度浸潤癌であった．PG typeが腺腫由来であるとすると，本症例は腺腫由来の癌，粘液癌の初期像として興味深く，深達度診断が困難であった1例と考えられた．

　A 44-year-old man visited our hospital, because of a positive result in a fecal occult blood test, in 1999. Barium enema and colonoscopy revealed a sessile protruted lesion (type Ⅰs) of the sigmoid colon. There was no suspicion of massive cancerous invasion of the submucosa. We performed an endoscopic mucosal resection for the lesion, measuring 15×13 mm. The resected specimen was regarded as a polypoid growth type, but tubulovillous proliferation in the intramucosa and mucinous adenocarcinoma with tubercle mucin invading the submucosa was revealed by microscopic investigation.

　Progression of mucinous adenocarcinoma at such an early stage is a very rare and interesting condition, especially in tumors of polypoid growth or related adenoma-carcinoma sequence. Massive Submucosal invasion of carcinoma, as found in this case, is difficult to detect.