胃底腺型胃癌の病理組織学的理解と鑑別診断

Expanding on the Histopathological Understanding and Differential Diagnosis of Fundic Gland-Type Adenocarcinoma

要旨●胃底腺型胃癌は胃底腺粘膜に発生する主に低異型度な分化型腫瘍で主細胞への分化が明瞭なものを指す．この腫瘍の臨床病理学的特徴を深く理解することを目的として，胃底腺粘膜の増殖・分化と化生，また，同じ胃底腺粘膜に発生する腫瘍様病変と低異型度腫瘍の病理学的特徴について解説する．胃底腺細胞は腺頸部より表層の腺窩上皮，深部方向の頸部粘液細胞，壁細胞，主細胞と内分泌細胞から構成される．頸部粘液細胞は主細胞の前駆細胞である．化生としては偽幽門腺化生，幽門腺化生と完全型腸上皮化生が発生する．これらの正常・化生組織を基盤として，腫瘍様病変としては腺窩上皮型過形成性ポリープ，胃底腺ポリープ，過誤腫性内反性ポリープ（粘膜下異所性胃腺）が，低異型度腫瘍としては腺窩上皮型腫瘍，胃底腺ポリープに伴う腺窩上皮型腫瘍，胃型腺腫（幽門腺腺腫），カルチノイドと低異型度小腸型腺癌が発生し，実際的あるいは概念的に胃底腺型胃癌の鑑別診断の対象となりうる．

　Gastric adenocarcinoma of fundic gland type is a tumor mainly composed of low-grade atypical cells differentiating into chief cells. To expand on the understanding of the clinicopathological characteristics, we describe the proliferation, differentiation, and metaplasia of the fundic gland mucosa as well as tumor-like lesions and low-grade neoplasms arising in the fundic gland mucosa. The fundic gland mucosa consists of foveolar, mucous neck, parietal, chief, and endocrine cells. Mucous neck cells differentiate into chief cells. Pseudopyloric gland metaplasia and complete type intestinal metaplasia may occur in the fundic gland mucosa. On the basis of the differentiation of these non-neoplastic cells, tumor-like lesions such as hyperplastic polyps, fundic gland polyps, hamartomatous inverted polyps（submucosal heterotopic gastric glands）and low-grade neoplasia such as foveolar dysplasia, fundic gland polyps with dysplasia, pyloric gland adenomas, neuroendocrine tumors, and low-grade small intestinal type adenocarcinomas should practically and conceptually be recognized as differentially diagnostic lesions of gastric adenocarcinoma of fundic gland type.