胃潰瘍の癌化について

On Malignant Change of Gastric Ulcer

　慢性胃潰瘍が癌化するか否か，即ち胃潰瘍癌が存在するか否かの問題は，Hauser¹⁾がその基準を示し，Newcomb¹¹⁾が更に詳細にその基準を設定して以来，論議の対象となってきた．そして，その頻度も3.5～100％の差を示している¹¹⁾．わが国でも，久留⁴⁾，村上⁶⁾⁷⁾，太田¹²⁾，長与¹⁰⁾らの研究により，胃潰瘍癌は比較的多いとされていた時期があった（32～79％）¹³⁾．しかるに近年，中村ら⁸⁾⁹⁾の微小胃癌の研究によって，一転，胃潰瘍癌は殆んど存在しないという説にかたむいている．その後は，臨床的および病理組織学的な胃潰瘍癌の研究は現われておらず，わずかに，大原¹⁶⁾，斎藤¹⁷⁾，白井ら²⁰⁾による実験的な胃潰瘍癌発生の検討がなされているのみである．このように胃潰瘍癌の頻度が大きくゆれ動いたのは，検索材料による差もさることながら，①慢性胃潰瘍からの癌化といっても，潰瘍を覆うべき未熟な再生上皮からの発癌であるか，あるいは，潰瘍辺縁の胃炎性の変化からの発癌か，それとも単に潰瘍と癌とが重なっていることだけを考えたのか，それが論じられることが少なかったこと，②潰瘍癌とする病理組織学的な判定基準が，きわめてあいまいであったこと

―すなわち潰瘍先行と考えられた粘膜筋板と固有筋層との融合の所見が¹¹⁾¹²⁾，事実であるかどうかの点，③臨床的な経過観察により，慢性胃潰瘍から癌化したと思われる症例がきわめて少なく，一方内視鏡的経過観察の結果，悪性サイクル⁵⁾⁷⁾という概念が明らかになってきたこと―などによると思われる．

　したがって，胃潰瘍癌は，すべての面から再検討されるべきものであり，本稿では，はたしてそれが存在するか否かの原点にたち帰って検討し，次に，存在するとすれば，どのような組織病理学的な特徴を有するかを考えてみたい．

　It has been quite controversial since long whether or no chronic gastric ulcer has a possibility to change into malignancy. I believe that this problem should imply the following four points.

　1) Is it possible to experimentally produce gastric cancer from chronic gastric ulcer ?

　2) In actual human gastric cancer, that from chronic gastric ulcer (ulcer-cancer) should show characteristic histopathological features of its own which could be unanimously approved. Then, what would be the diagnostic criteria ?

　3) In chronic benign gastric ulcer in man, are there atypical changes of the regenerating mucosa that might suggest gradual alteration into malignacy ?

　4) Is there any case in which malignant change actually occurred during the clinical follow up of a benign gastric ulcer ?

　Since I do not have sufficient data in regard to the fourth point, this discussion will deal with the points No. 1, 2 and 3.

　1) Chronic gastric ulcers were successfully produced experimentally in rats of the Wistar strain (The ulcers remained active after the course of 540 days). Subsequent oral administration of N-methyl-N'-nitro-N-nitrosoguanidine resulted in malignant change of the chronic ulcers in 12 of 100 cases (12%)

　2) In human specimen, the term ulcer-cancer was limited to those in which cancer was found only in the regenerating mucosa in a strict sense. Among 173 lesions of the depressed type of superficial gastric cancer associated with ulcer or ulcer scar, ulcer-cancer that satisfies the above definition was found in 7 lesions accounting for 4.0%. All of these were well differentiated adenocarcinomas. In one of them, there was an apparent transition from regenerating mucosa into cancer. These cases account for 2.0% of all superficial cancers.

　3) Six hundred seventy nine benign gastric ulcers in human resected specimen were stepsectioned for detailed study with each slice being 5 mm in thickness. Nine ulcers accounting for 1.3% showed atypical epithelium over the range of atypia associated with regeneration. This seems to indicate a possibility of malignant alteraion in the future.

　In conclusion, gastric ulcer-cancer, though limited in number, certainly exists at least in 2.0% of all superficial cancers.