広範囲に微細顆粒隆起を呈した大腸粘膜内Schwann細胞性過誤腫の1例

Widely Distributed Mucosal Schwann Cell Hamartoma of the Colon with Fine Granular Elevations

要旨●患者は70歳代，男性．貧血の原因精査目的の大腸内視鏡検査にて盲腸〜肝彎曲にびまん性に白色調の微細顆粒状隆起病変を認めた．微細顆粒状隆起はNBI併用拡大観察，クリスタルバイオレット染色にて窩間部の上皮下の病変を反映している所見と考えられた．生検にて神経系腫瘍が疑われ，診断目的にEMRを施行した．HE染色では粘膜上皮直下の粘膜固有層に異型性のない線維性紡錘形細胞の束状・渦巻状増殖巣を認めた．S100蛋白は陽性，epithelial membrane antigenは陰性であった．免疫組織化学染色を施行し，シナプトフィジン染色は陰性で神経節細胞は認めなかった．神経線維腫症1型，多発性内分泌腫瘍2B型の合併はなく，大腸粘膜内Schwann細胞性過誤腫と診断した．

　A 70-year-old man was referred for a thorough examination due to anemia. Colonoscopy revealed numerous white granular nodules in the mucosa, extending from the cecum to the hepatic flexure. These findings were interpreted as subepithelial lesions, as observed through magnified endoscopy using narrow-band imaging（NBI）and crystal violet staining. Histopathologic evaluation of the lesion biopsy specimen suggested a nerve tumor, leading to an endoscopic mucosal resection. Histological analysis revealed a bundled or spiral proliferative nest of atypical fibrous spindle-shaped cells in the lamina propria, immediately beneath the mucosal epithelium. The lesion was positive for S100 protein and negative for epithelial membrane antigen by immunostaining, whereas synaptophysin staining did not indicate the presence of ganglion cells. Additionally, no clinical features of multiple endocrine neoplasia type 2B or neurofibromatosis type 1 were observed. Consequently, the patient was diagnosed with colonic mucosal Schwann cell hamartoma.