ESD治療後に多発肝転移で再発した直腸内分泌細胞腫瘍の1例

Rectal Neuroendocrine Tumor with Multiple Liver Metastasis with Recurrence after Endoscopic Submucosal Dissection, Report of a Case

要旨　患者は49歳，女性．大腸がん検診の便潜血検査が陽性で，近医で下部消化管内視鏡検査を施行し，下部直腸に腫瘍径約11mmの粘膜下腫瘍を認めた．色調は黄白色調で基部にややくびれを有し，頂部には陥凹を伴っていた．前医の生検で直腸NETの診断であり，ESDを施行した．切除標本の病理所見は深達度SM，断端陰性，脈管侵襲陰性であったが，核分裂像はほとんどみられず，Ki-67 L.I.が5.2％と高値を呈していた．ESD後は1年ごとのCT検査を行っていたが，2年8か月後のCTで多発肝転移を認めた．追加治療を行ったが，6年8か月後に死亡した．2010年にWHO分類が改正され，Ki-67 L.I.がグレード識別項目となったが，今後転移予測因子となりうるのかについて症例の蓄積が待たれる．

　A 49-year-old woman with positive results on a fecal occult-blood test for colorectal cancer screening underwent total colonoscopy in a nearby hospital, which revealed a submucosal tumor in the distal rectum. The yellowish white tumor was 11mm in diameter and was subsessile with a depression at its top. Based on the diagnosis of NET（neuroendocrine tumor）revealed by a biopsy at the previous hospital, ESD（endoscopic submucosal dissection）was carried out. Histological examination of the resected specimen showed that the depth of invasion was sm, without lymphovascular invasion. The tumor was completely excised with clear margins. Mitosis was minimal and Ki-67 L.I. was high at 5.2％. Surveilance CT examination, performed every year after ESD, detected multiple liver metastasis two years and eight months later. The patient died after six years and eight months in spite of additional treatment. Ki-67 has been included in the WHO grading system of NET since 2010, and further elucidation of its significance as a predictive factor of metastasis is expected.