静脈内進展を来した8mm大0-Is＋IIc型大腸SM癌（小腸型）の1例

0-Is＋IIc Colorectal Submucosal Invasive Carcinoma（Small Bowel Type） with 8-mm Diameter and Venous Invasion, Report of a Case

要旨●患者は66歳，男性．便潜血陽性の精査目的で当センターを受診した．大腸内視鏡検査でS状結腸に境界明瞭で段差を伴う星芒状〜面状陥凹を呈する10mm大の0-Is＋IIc型病変を認めた．二段陥凹を呈したが，陥凹部の拡大観察でV_I型軽度〜中等度不整であった．cT1bと診断し手術を施行した．病理組織学的診断では高分化管状腺癌pT1b（SM 1,350μm），Ly0，V1a（SM）（EVG染色）であった．2段陥凹を呈する0-Is＋IIc型早期大腸癌はSM深部浸潤癌であることが多いが，陥凹内のpit pattern診断でcT1bを示唆する所見に乏しい場合は，EUSを含めて慎重に深達度診断をする必要がある．

　A man over 60 years of age underwent a colonoscopy to diagnose occult blood in his stool. It revealed a protruding lesion with an irregular central depressed area in the sigmoid colon. The tumor was 10mm in diameter, and the gross configuration was type Is＋IIc. Moreover, hyperplastic mucosa was noted at the margins of the protruded lesion. Central depressed area was star-shaped with a trough-like deep depression. Furthermore, magnifying colonoscopy observation revealed a type VI mild−moderate irregular pit pattern in the central depressed area. Barium enema study revealed an irregular star-shaped central depressed area with deep depression. Considering these observations, the lesion was diagnosed as submucosal invasive carcinoma. Laparoscopy-assisted sigmoidectomy was performed. Histopathological examination revealed well-differentiated tubular adenocarcinoma, pSM（1,350μm）, ly0, and v1 with no metastasis to the lymph nodes. Moreover, the tumor may have developed and proliferated by compressing the muscularis mucosa and invaded the submucosa via the vein if obvious findings suggestive of pT1b in the pit pattern diagnosis within the depression were absent despite the Is＋IIc tumor.