直腸villous tumorの1例

A Case Report of Villous Tumor of the Rectum

　大腸のvillous tumorは比較的まれな疾患で，通常みられる腺腫とはその組織発生，形態，生物学的態度などを異にしているため，近年，癌と良性腺腫との境界領域病変^1)～6)と考えられるようになってきた．従って本腫瘍の臨床的取り扱いも，次第に意見の統一^{2)～4)7)～9)}がみられるようになってきたといえる．しかし本腫瘍が一つのentityを確立したようにみえても，その概念は今一つあいまいで，まだ臨床的にも病理学的にも未解決の問題を含んだ疾患^8)10)～12)と考えられる．

　著者らは61歳の女子で数回の粘血便を主訴として来院し，直腸に6cm大のvillous tumorのあった1例を経験した．本例はわが国の胃生検分類¹³⁾のGroup Ⅲ～Ⅳ，Jackman¹⁴⁾らの大腸ポリープ分類の中等度，ないし，高度異型を示す腺管より構成され，ほぼ同じ組織水準で腸壁固有筋層にまで浸潤していた．本例の病理学的問題点，および，臨床像について文献的考察を加え報告する．

　Villous tumor of the colon is rare in Japan. This report deals with a 61 year-old female who had a villous tumor in the rectum with muscular microinvasion. She had complained of small amount mucous bloody stools several times before admission. Barium enema and rectosigmoidoscopy disclosed a nodular flat-polypoid mass in the rectum. Grossly this tumor was irregulary ovoid in shape, measuring 9.5×4.5 cm in size. The surface of the tumor was roughly uneven, giving a cauliflower-like appearance. Microscopically, villus-like projections lined by a single layer of tall columnar epithelium characterized this tumor. The lining cells were large in size, having dark cytoplasm, and large ovoid hyperchromatic nuclei with prominent nucleoli. Pseudostratification and mitosis were seen. We could not conclude that this tumor had originated from villous papilloma, because the tumor in this case was made up of neoplastic elements showing neither high cellular nor marked structural atypism and because the transition between glands of different grades of atypicality was gradual. Moreover the portion of muscular microinvasion of the tumor was the same in histological findings as were seen other tumor areas. Two possibilities, namely, an origination from de novo carcinoma and a malignant transformatin of pre-existent benign villous tumor, may be considered concerning the histogenesis of this tumor.