胃の腺腫：私はこう考える

Gastric Adenoma: Its Concepts and Relation to “Atypical Epithelial Lesion”

要旨　“腺腫”は腫瘍総論的には腺上皮系の“良性新生物（benign neoplasm）”であり，生物学的に1つの安定状態にあると考えられている．しかし，その位置付けからはある程度の前癌性も見込まれている．われわれは従来より胃における上皮性異型病変で過形成・再生の範疇にも癌の範疇にも入らない病変に対しては“異型上皮”あるいは“異型上皮巣”なる名称を与え，この中に腺腫を含める立場を取ってきた（広義の“異型上皮巣”）．異型上皮巣はそれを構成する上皮により“腸型”か“胃型”かに分けられ，更に肉眼型により隆起型か平坦型か陥凹型かに分けられる．最も頻度の高いものは腸型のⅡa様隆起性病変である．諸臓器，特に大腸における腺腫の形態学的および生物学的特徴に鑑み，胃の異型上皮巣のうちどの病変が“腺腫”と呼ばれるにふさわしいかの検討を行った．腸型の隆起型病変（早期胃癌Ⅰ様およびⅡ様），腸型の平坦型病変（同Ⅱb様）の一部，および胃型の大きな隆起型病変は腺腫と呼ばれてかまわない病変と考える．その他の病変は異型上皮巣としておくのが妥当であろう．

　“Adenoma” is a benign neoplasm arising from glandular epithelium. Although stable in biological behavior, it has a potential of evolving into cancer. Terms like “atypical epithelium” and “atypical epithelial lesion” have been used for more than 20 years to describe the lesion which could not be categorized into any of the following concepts; hyperplasia, regeneration and carcinoma. The lesions called “atypical epithelium” or “atypical epithelial lesion” have been considered to include “adenoma” as well. The most frequent one is the flat elevated lesion consisting of intestinal type epithelium. Atypical epithelial lesion is subclassified into two types, intestinal and gastric, according to the epithelium composing the lesion. Furthermore, these types are macroscopically subdivided into elevated, flat and depressed types. This article discussed which type or types of these “atypical epithelial lesion” are equivalent to adenoma in comparison with the characteristics of what is called adenoma everywhere in the body, particularly in the large intestine.

　The author considers that the term,“adenoma“ of the stomach, might be used for the protruded or elevated lesion (early gastric cancer type Ⅰ-like or type Ⅱa-like lesion) of intestinal type, and for some of the flat lesions of intestinal type and some of the protruded or elevated lesions of gastric type as well. But the term should not be used for the rest of the types of atypical epithelial lesion because the nature of these types remains to be clarified.