胃良性ポリープの癌化の1例―同一胃内に見出された3個のポリープ癌とそのポリープの特異な組織像について

Malignant Transformation of Benign Gastric Polyps, Report of a Case

　胃のhyperplastic polypの癌化の問題は従来より好んで取り上げられた研究課題の一つであった．その研究の歴史をふり返ってみると，胃ポリープの癌化として隆起性病変を一把ひとからげに扱い，癌化率が高いと考えた時代から，胃の良性ポリープをfoveolar epitheliumに覆われた腺管の過形成からなる群hyperplastic polypと，異型性を伴う腺管から成り立った群，いわゆるⅡa-subtype，ATP（西欧ではadenoma，adenomatous polypと呼ぶ人が多い）との癌化を別々に取り扱うようになり，組織学的判定基準の変革および臨床例の長期観察から，両群のポリープとも癌化することはあってもその率は従来考えられていたよりずっと低いことがわかってきた．

　ここに報告する症例は5個の良性ポリープ中3個に癌化が認められ，しかもそのポリープはhyperplastic polypに類似してはいるが，厳密には同一範疇に属させ難いものである．今後胃ポリープの分類を考える上でも参考になると思われるので，組織像を中心に報告したい．

　A total of four early cancers of the stomach (Ⅱa＋Ⅱc and three type Ⅰ cancers) was found in the pyloric region and body of a woman 63 years of age. All type Ⅰ cancers were considered to have arisen from benign polyps.

　Histologically they showed papillary carcinoma. The Ⅱa＋Ⅱc variety was accompanied with submucosal infiltration, while the other three were confined to the mucosa. Although cancer nests in type Ⅰ group involved only a minimal part of benign polyps, the existence of cancer was histologically beyond dispute. There were two other benign polyps in addition to three early cancers, but all of fiver polyps showed the same histologic characteristics of marked proliferation of the tubules lined by the foveolar epithelium. They simulated histologic patterns of hyperplastic polyps not only in the invertad V-shaped elevation of the muscularis mucosae but in hyperplasia of the foveolar epithelium as well. However, there were hardly any cystic change and interstitial edema that characterize hyperplastic polyps. Proliferating activity of the foveolar epithelium was also seen in such a manner as to differentiate them from hyperplastic polyps. Some relationship was thought to exist between this proliferating activity and the fact that cancer was found in three out of five polyps, We have pointed out that these polyps reported must belong to the defierent category from the ordinary hyperplastic polyps.