胃の潰瘍と癌の因果律―陥凹性早期胃癌の問題点

Causality of Ulcer and Cancer of the Stomach

　従来から，胃癌の発生母地として潰瘍・ポリープ・慢性胃炎が重要視されていて，これら良性病変と癌との関係が論じられています．特に，胃の潰瘍と癌の頻度が高いわが国では，浅い潰瘍の存在も論じられています．この潰瘍一癌に関する多くの論文をみますと，潰瘍の癌化の頻度または全胃癌に占める潰瘍癌の頻度には，かなりの“ばらつき”があって一定の傾向を把握することができません．潰瘍癌の頻度にっいては，Newcomb¹⁰⁾の論文にみられるように，3.5～100％の拡がりを示しています．また，わが国では，頻度のばらつきが32～79％を示しています^{4)5)7)11)18)19)}．

　このように，潰瘍癌の頻度が広範囲に分散していることは，潰瘍癌と判定する組織学的基準の差によるものであり，しかも，その差は基本的な所見の違いではないと思われます．潰瘍癌の組織学的判定基準によって，潰瘍癌の頻度に広範な”ばらっき”をもたらすような不条理さが良性潰瘍と癌との間に存在することに疑問が生じます．もし良性潰瘍と癌の問に密接な因果関係が存在するとすれば，たとえ潰瘍癌の判定基準に多少の差があっても，潰瘍癌の頻度にはある近似がみられてしかるべきと考えられるからです．

　Gastric cancer associated with ulcer substantially involves two problems: “ulceration of cancer” and “canceration of ulcer”. Accordingly, the causality of gastric ulcer and cancer has been investigated on the basis of findings that can be interpreted more objectively and free from conventional concepts of it.

　1. Classification of 285 lesions of intramucosal carcinoma according to their size and incidence of accompanying ulcer in cancer nest in each of the divided groups indicate that the rate of concomitant ulcer in cancer nest increases according as the latter becomes larger. It can thus be presumed that the size of surface area in mucosal carcinoma enlarges for the most part in proportion to the time elapsed since the origination of cancer. In addition to this, the fact that of 63 lesions of minute carcinoma under 5mm in the largest diameter only one solitary lesion (1.6 per cent) was associated with ulcer seems to show that the majority of cancer nests accompanied with ulcer should be regarded as not owing to canceration of ulcer, a phenomenon of rare occurrence, but to ulceration of cancer.

　2. Simple diagrammatic representation of topographic relation between ulcer and cancer in intramucosal carcinoma has been attempted to determine incidence of concomitant ulcer (and if possible to find any respective characteristics) in the groups classified according to cancer size. As a result it has been found that the majority of cancer lesions under 2 cm in the largest diameter were of disc-shape, while those over 2.1 cm were predominantly of torusshape. As ahole must be bored into a disc in order to shape a torus, so is an ulceration of cancer presumably requisite for enlargement of cancer lesion.

　3. Of 17 cases of intramucosal carcinoma completely surrounded with fundic gland mucosa, 15 were associated with ulcer. It is only of rare occurrence for an ulcer to originate in the fundic gland area. Nevertheless, the majority of cancer originating there as in the present cases seem to strongly advocate ulceration of cancer.

　Viewed along the linesas listed above, it is assumed that the majority of cancer accompanied with ulcer is due to “ulceration of cancer”.