内視鏡的切除により確定診断が得られた粘膜下腫瘍様早期胃粘液癌の1例

Early Mucinous Gastric Carcinoma Masquerading as a Typical Submucosal Tumor Diagnosed by Endoscopic Resection

要旨　患者は60歳代，男性．検診異常のため近医にて上部消化管内視鏡検査を施行したところ，胃前庭部大彎に径1cm大の粘膜下腫瘍（SMT）様隆起を指摘され，精査加療目的で紹介となった．SMT様隆起は表面平滑な山田I型隆起で，超音波内視鏡検査では，第2層から第3層浅層に限局する境界明瞭な低エコー腫瘤として描出された．生検でも確定診断に至らず，内視鏡的粘膜下層剝離術を施行した．病理組織学的には，SMT様隆起は粘膜下層を主座とする多量のムチンを伴った高分化型腺癌で粘液癌と診断された．大部分は正常粘膜で覆われ，粘膜面への癌露出が乏しかったため術前診断が困難であった．

　We report a rare case of early mucinous gastric carcinoma（MGC）presenting features of submucosal tumor（SMT）diagnosed by endoscopic resection, the malignancy of which had been difficult to determine by prior endoscopic examinations. A 60-year-old man with a gastric SMT was referred to our institute for further examination and treatement. Endoscopic examinations revealed a smooth-surfaced SMT-like lesion in the gastric antrum. Endoscopic biopsies for the lesion were repeated but showed no malignancy. Endoscopic ultrasound imaging of the lesion showed a heterogeneous hypoechoic mass in the 3rd layer, with an intact deep 3rd layer. En-bloc resection was attempted for definitive diagnosis using the endoscopic submucosal dissection technique. Histopathological examination of the lesion revealed a mucinous carcinoma invading the submucosa.

　Although early MGC is very rare, we should keep this in mind when faced with the differential diagnosis of SMT originating from the superficial layers and be vigilant so as to notice the presence of concavity at the surface of the SMT. In the case of a negative biopsy due to a normal surface and mucous matrix, additional biopsy procedures may be useful for definitive diagnosis.