低異型度管状腺癌の生検診断

Pathological Diagnosis of Biopsy Specimens of Low Grade Tubular Adenocarcinoma of the Stomach

要旨　低異型度管状腺癌の生検診断について症例を用いて概説した．低異型度管状腺癌の生検検体をみると，再生性異型との判別が難しいものと，正常組織に類似しているために悪性の判定が難しいものとに大きく分けられた．後者には，固有腺に類似した癌と腸上皮化生腺管に類似した癌がある．低異型度管状腺癌の生検診断では，核異型度は低めであるが，類円形核がわずかな大小不同，軽度の配列の乱れを示す所見に注意すべきである．また，細胞異型度が低めであっても，構造異型所見で確定診断をつける癌が存在することを知っておくべきである．そのためには低異型度管状腺癌の診断の経験を積み上げることが重要である．また，臨床医と病理医で意見交換をもつことが大切である．異型の情報量が少ない場合には，無理な判定をせず，再生検を指示すべきである．胃生検組織診断分類（Group分類）が大幅に改訂されたが，その対応についても概説した．

　Low grade tubular adenocarcinoma of the stomach used to be rare, but with the progress of endoscopy, such cancers can be detected in ordinary examinations. The diagnosis of biopsy specimens of that cancer is difficult because of the very low degree of atypical features. In this paper, the diagnosis points of biopsy specimens of low grade tubular adenocarcinoma are explained using several cases.

　As for such biopsy specimens, there are two main types, one is cancerous glands with regenerative change and one is cancer glands resembling normal glands. In the latter type there are two types. One type is cancers resembling the gland proper, such as foveolar epithelium, pyloric gland and fundic glands. Another type is cancers resembling intestinal glands, such as incomplete type intestinal metaplasia and complete type intestinal metaplasia. Those cancers have very low grade nuclear atypia, so pathologists pay special attention to small round nucleori, mild irregularity of nuclear size and mild irregular arrangement of nucleori. We should keep in mind that cancers which are recognized by only structural atypia also exist. Pathologists have to recognize the histological features of regenerative mucosa in diagnosing cancer with regenerative change. In cases with few atypical features in biopsy specimens, deeper cut sections are required. If a distinct diagnosis is difficult with only a few specimens, re-biopsy is recommended.

　In order to be able to diagnose such cancers, pathologists should make efforts to experience many cases of low grade tubular adenocarcinoma. And good communication between pathologists and clinical doctors is needed.