印環細胞癌と粘液癌を伴った早期大腸癌の1例

Early Colonic Cancer with Signet-ring Cell Carcinoma and Mucinous Carcinoma of the Cecum, Report of a Case

要旨　患者は53歳，男性．大腸内視鏡検査にて，盲腸に径20mm大の中央部にわずかな陥凹を伴うIsp病変を認めた．陥凹部の拡大観察ではVi高度不整に伴い，無構造な領域を認めたためSM深部以深への浸潤が疑われた．生検組織では高分化管状腺癌に伴って印環細胞癌が指摘されたため，腹腔鏡下右半結腸切除術を行った．病理組織学的には，陥凹部にほぼ一致して印環細胞癌が粘膜内に存在し，粘膜下層に粘液癌の形態を伴い塊状に浸潤（4,600μm）していた．内視鏡での陥凹部の褪色調変化が印環細胞癌を示唆する所見であった．低異型度腺癌の一部が脱分化し印環細胞癌になっており，組織発生の観点からも興味深い症例と考えられた．

　A 53-year-old man visited our hospital and was found by colonoscopy to have a protruded polyp（Isp）with shallow depression about 20mm in diameter in the cecum. This lesion was suspected to be a submucosal invasive cancer because a non-structure area with a Vi（invasive pattern）area was seen in the depression area by using magnifying colonoscopy. Biopsied specimens showed a signet-ring cell carcinoma with a tubular adenocarcinoma, so laparoscopic right colectomy was performed. Histopathological findings showed a signet-ring cell carcinoma, which corresponded with the depressed area, and had invaded the submucosal layer over a massive area as a mucinous carcinoma. A discolored change of the depressed area was regarded as a characteristic finding of signet-ring carcinoma of the colon. We thought that a part of a low grade adenocarcinoma had developed into a signet-ring cell carcinoma, thus it is the interesting case in histogenesis.