一部でSM浸潤を来していたLST顆粒型病変の1例—SM浸潤部の拡大内視鏡所見を中心に

Identification of Rectal Submucosal Invasive Cancer by Using Magnifying Observation, Report of a Case

要旨　患者は70歳代，男性．健診で便潜血反応陽性を指摘され，近医を受診した．下部消化管内視鏡検査を施行したところ直腸下部に約40mm大のLST-G（結節混在型）を指摘され，当科へ紹介，受診となった．通常光観察では，結節隆起部位で発赤調の陥凹面を認めた．NBI拡大観察では陥凹面で血管の口径不同が目立ち，一部では血管密度が低下し，surface patternは不整であった．色素拡大観察では，結節隆起の陥凹面でV_N型pitと診断した．SM深部浸潤癌が疑われたが，完全摘除生検目的にESDを施行した．周囲の顆粒均一部は腺腫成分が主体で，結節隆起部は異型の高い高〜中分化型腺癌の増生を認めた．結節部の直下で，筋板を破って粘膜下層浸潤を来していた．最終病理診断は，well to moderately differentiated adenocarcinoma with tubular adenoma，T1b（SM 2,250μm），ly0，v0，簇出Grade 1であった．

　The patient was a male >70years, who was referred to our department for further examination as a result of positive occult blood reaction in the feces. Total colonoscopy demonstrated a laterally spreading tumor granular type（LST-G）, with a depressed lesion in the lower rectum. The tumor was 40mm in diameter. Viewing by NBI revealed that the depressed lesion in the large nodule of this tumor had an area showing moderately distorted microvessels without surface structures. Furthermore, chromoendoscopy using indigocarmine spraying more clearly revealed the tumor border and depressed lesion in the nodule. In addition, crystal violet staining was shown to type V_N pit pattern at the localized depressed area. Finally, we diagnosed this tumor as submucosal invasive cancer, with an adenomatous component in the lower rectum. However, this lesion was resected by the ESD method because rectal ESD is less invasive than a surgical method using a laparoscope for total resection and histological examination. Pathological diagnosis was well to moderately differentiated adenocarcinoma, with no lymphatic or venous invasion. The depth of invasion was 2,250μm under the depressed area.