特異な形態を呈し組織学的にpseudocarcinomatous invasionを伴った大腸腺腫内癌の1例

Colonic Cancer in Adenoma with Peculiar Shape and Pseudocarcinomatous Invasion, Report of a Case

要旨　患者は58歳，男性．下行結腸に表面結節状変化を伴う有茎性ポリープが認められ，その茎部は比較的太く，軽い捻転を呈していた．腺腫内癌が疑われ，ポリペクトミーも困難と思われたことから腹腔鏡下結腸部分切除術が行われた．腫瘤は20×18×30（高さ）mmの大きさであり，頂部の結節様部分と基部の粘膜下腫瘍様部分から成っていた．組織学的に頂部は主に中等度異型を伴う腺管腺腫であり，一部p53陽性の微小粘膜内癌が散在していた．一方，基部には粘膜筋板の異常な樹枝状増生があり，それに取り囲まれた粘液貯溜および頂部とほぼ同程度の異型性腺腫様組織を認め，周囲に出血を伴うことなどからも大腸腺腫のpseudocarcinomatous invasionと診断された．

　A 58-year-old man was admitted to our hospital for surgical treatment of a colonic polyp. The polyp was located in the descending colon, about 2 cm in diameter, and pedunculated. Endoscopic examination demonstrated that the stalk of the twisting polyp was too thick to be operated on by polypectomy. Because the polyp was relatively large and nodularly changed in its head, it was suggested that the lesion might be accompanied by malignancies. Partial colectomy was performed assisted by laparoscopy. The lesion was 20 × 18 × 30 (height) mm in size, which, macroscopically, consisted of a nodular part in the top and a smooth part like a submucosal tumor at the base. In the cut surface, the part like a submucosal tumor was filled with mutinous pooling. Microscopically, the lesion of the head was mostly diagnosed as tubular adenoma with moderate atypic, partly accompanied with intramucosal cancer showing positive, immunohistochemically, for anti-p53 antibody. The lesion in the base of the polyp contained much mucin and adenomatous tissues among the proliferating muscularis mucosae. The atypic of the adenomatous lesion was relatively close to the head, and bleeding was detected in the peripheral tissues. So, this polyp was finally thought to be a colonic cancer in an adenoma with pseudocarcinomatous invasion, histopathologically.