15か月で急速な発育進展を来したと考えるSSL由来進行大腸癌の1例

A Case of Advanced Colorectal Cancer Derived from a Sessile Serrated Lesion Showing Rapid Progression within 15 Months

要旨●患者は80歳代，男性．肝腫瘤の精査目的のために当科に紹介され受診となり肝細胞癌と診断された．貧血があり大腸内視鏡検査を行ったところ，上行結腸に5mm大の0-IIa型病変を認めSSLと診断した．その後，高齢のため肝細胞癌は経過観察となっていたが，初回の内視鏡検査から15か月後に血便を生じ，再度大腸内視鏡検査を行ったところ，上行結腸に進行大腸癌を認めた．病変の裾野には鋸歯状と考えられる開大した腺管構造を認め，腫瘍の遺伝子変異解析ではBRAF変異陽性であった．病理組織学的にも大腸鋸歯状病変由来の癌として矛盾せず，本症例は15か月の経過で増大したSSL由来進行大腸癌と考えられた．

　A man in his 80s was referred to our department for a close examination of his HCC（hepatocellular carcinoma）. Owing to his anemia, he underwent colonoscopy, which revealed a 5-mm type 0-IIa lesion in the ascending colon. This lesion was then diagnosed as a SSL（sessile serrated lesion）. After 15 months, he developed bloody stools and underwent another colonoscopy, which revealed an advanced colorectal carcinoma in the ascending colon. The lesion had an enlarged serrated glandular structure at the base, and genetic analysis revealed a BRAF mutation. We considered the lesion as a colorectal carcinoma derived from SSL showing rapid progression within a 15-month course.