LST-G，T1b癌—陥凹部の拡大観察が深達度診断に有用であったLST-Gの1例

LST-G, T1b：A Case of Granular-type Laterally Spreading Tumor in Which Magnifying Obsevation of a Depressed Area was Useful for Depth Diagnosis

要旨●患者は70歳代後半，男性．近医で行われた下部消化管内視鏡検査にて上部直腸（Ra）に45mm大の表面隆起型腫瘍を指摘されたため，当科に紹介され受診となった．通常観察（白色光）では境界明瞭な側方発育型腫瘍（LST）（顆粒均一型）であったが，一部に発赤調の陥凹面を認めた．陥凹部はNBIおよび色素拡大観察の所見から粘膜下層深部に浸潤した癌と考え，腹腔鏡下低位前方切除術を行った．病理組織学的検査では，乳頭腺癌を伴う高分化管状腺癌および中分化管状腺癌の増殖がみられ，癌は陥凹部に一致して粘膜下層2,000μmにまで浸潤していた．

　A 70-year-old man was referred to our department for further examination and treatment following the detection of a superficially elevated rectal lesion in a local clinic. Colonoscopy revealed a 45mm, granular-type, laterally spreading tumor（LST）with a reddish and depressed area in the upper rectum, which was diagnosed as JNET type 3 lesion using NBI magnifying endoscopy classification. Crystal violet staining for magnifying pit pattern analysis confirmed a vascular network pit pattern. Based on these findings, together with endoscopic ultrasonography, the diagnosis was submucosal invasive cancer, which was laparoscopically resected. Histopathologic examination of the resected specimen revealed a well-to-moderately differentiated adenocarcinoma with deep submucosal invasion to a depth of 2,000μm in the reddish and depressed area.