胃上皮下腫瘍の組織発生と病理診断

Histogenesis and Pathological Diagnosis of Gastric Subepithelial Tumors

要旨●近年，胃底腺型胃癌に代表される粘膜内に存在しながら表面は非腫瘍上皮に被覆される腫瘍への関心の高まりとともに，従来の粘膜下腫瘍（SMT）に代わって上皮下腫瘍（SET）という用語が使われるようになっている．SETとは狭義のSETと粘膜下層以下に局在を持つ本来のSMTの両者を包含する概念と言える．粘膜下に中心を置く腫瘍として，浸潤部で膨張性に体積を増す癌，胃壁を構成する間葉成分に由来する間葉系（非上皮性）腫瘍，転移性腫瘍が挙げられる．これらの腫瘍と鑑別となる腫瘍様病変としては，異所性胃腺，膵組織などが挙げられる．これら胃のSETの鑑別診断を考える際には，発生母地となる組織の存在部位を知っておくことが重要である．

　In recent years, the term subepithelial tumor has replaced the traditional submucosal tumor as there has been a growing interest in tumors that exist within the mucosa but are covered by non-tumor epithelium, such as fundic gland-type gastric carcinoma. A subepithelial tumor is defined as a concept that encompasses both narrowly defined subepithelial tumors and literal meaning submucosal tumors that are located beneath the mucosal layer. Tumors centered in the submucosa include carcinomas that grow aggressively at invading sites, non-epithelial tumors derived from the mesenchymal component of the gastric wall, and metastatic tumors. Tumor-like lesions that should be distinguished from neoplasms include heterotopic gastric and pancreatic tissue. When making the differential diagnosis of these gastric subepithelial tumors, considering the origin of the tumors is beneficial.