胃の良・悪性境界領域病変―私はこう思う

Some Considerations on Lesion of Atypical Epithelium of the Stomach

　胃の良・悪性境界領域病変には，最も頻度の高いものとして限局性上皮性の所謂“異型上皮巣”があり，それは臨床的ならびに病理組織学的に分化型癌との鑑別が問題となる．一方，頻度は高くはないが非上皮性に於ても境界領域病変が存在し同様の問題がある．たとえば，所謂“リンパ細網細胞増生”と悪性リンパ肉腫，平滑筋腫と平滑筋肉腫との間にである¹⁾²⁾．このような良・悪性境界領域病変には，たとえそれらが良性と見なされたとしても，時間の経過によって悪性化するか否かの問題があり，さらにはそれらの治療法はといった問題が残されている．

　ここでは，胃の上皮性良・悪性境界領域病変について，根源的なこと，分化型癌との鑑別，さらにはどのように対拠すべきかを筆者らの経験から眺めてみたい．

　Benign and borderline lesions of atypical epithelium, and differentiated carcinoma of the stomach form a set conditioned on the following three: (1) Localized, epithelial lesion; (2) Lesion consisting of many glands, the epithelial cells of which are gene-rally cylindric in shape and show atypicality of various degree; (3) Lesion arising from metaplastic epithelium of intestinal type of the gastric mucosa.

　In certain features atypicality means departure from the normal epithelium at the cellular and structural levels. The very same atypicalities do not exist and it is possible to arrange atypicalities in the order of severity, so that there is one-to-one correspondence from atypicality to segment of the real number. Namely atypicality can be interpreted as continuum.

　In practice, when the set is divided into two subsets of benignancy and malignancy by using atypicality, it will be inevitable to give rise to a boundary area in the set. This explains why it is impossible to recognize numerous atypicalities very close to a boundary point between benignancy and malignancy in division of the continuum.

　In order to make the boundary area narrower, it may be necessary to use findings except atypicality. In the set, the majority of the benign lesion shows macroscopically elevated lesion, the surface of which is smooth. Meanwhile, elevated lesion of differentiated carcinoma is generally rough in its surface. Atypical epithelium of benignancy is situated microscopically in the superficial part of the mucosa, and there are the pyloric glands and/or a few cysts of gland below it. Generally speaking, differentiated carcinoma unlike the benign lesion of atypical epithelium replaces the entire mucosa in depth, independently of its dimensions. Atypical epithelium of benignancy contains many goblet and Paneth cells, whereas differentiated carcinoma having these cells is rare. These differences mentioned above may be a guide to differential diagnosis of the lesions of atypical epithelium.

　When diagnosis of the borderline lesion of atypical epithelium is made by studying biopsy material, it becomes necessary to follow it up thoroughly or to gastrectomize. When a benign lesion of atypical epithelium as diagnosed by studying biopsy material measures more than 2 cm in the greatest diameter, it should be operated on. This is because the lesion harbors sometimes a microcarcinoma.

　In the benign lesion of atypical epithelium, frequency of harboring microcarcinoma is interpreted as less than 4% at the utmost.