下部直腸の0-IIa＋IIc型低分化型粘液癌の1例

A Case of Poorly-differentiated Mucinous Adenocarcinoma of the 0-IIa＋IIc Type in the Lower Rectum

要旨●患者は80歳代，男性．大腸内視鏡検査を施行したところ，下部直腸（Rb）に径15mm大の0-IIa＋IIc型病変を認めた．インジゴカルミン色素撒布観察やNBI拡大観察では陥凹内に乳白色で大小類円形の粘液付着を認め，粘液付着の薄い部分の拡大観察ではJNET分類Type 3，VN型pit patternの所見を認めた．術前生検で印環細胞癌を認め，注腸X線造影所見および超音波内視鏡所見も含め粘膜下層高度浸潤癌と診断し直腸切断術を施行した．病理組織学的所見は，低分化型粘液癌が主体で，浸潤先進部には印環細胞癌を伴い，筋層までの浸潤を認めた．特徴的な粘液付着所見が組織型診断に有用と考えられた．

　An elderly man in his 80s was found to have a type 0-IIa＋IIc diameter lesion in the lower rectum. Indigocarmine spraying and narrow-band imaging magnification revealed milky white mucus deposits in the depression. The thin mucus area revealed JNET type 3 and VN type pit patterns when magnified. A pre-operative biopsy revealed a signet-ring cell carcinoma. The lesion was diagnosed as deep submucosal invasive carcinoma after additional X-ray and endoscopic ultrasonography findings, and an abdominoperineal resection was performed. Histopathological examination revealed predominant poorly-differentiated mucinous adenocarcinoma, with signet-ring cell carcinoma in the invasive front and invasion into the muscularis mucosae. The characteristic mucus adherence on the surface was thought to be useful for predicting the histological type preoperatively.