高位の胃癌の組織発生

Histogenesis of Cancer in the Upper Segment of the Stomach

　筆者らは²⁾³⁾，“癌組織は，それが発生した正常臓器の構造・機能を多少とも模倣する”との，癌腫一般の基本概念にもとづき，微小胃癌（最大径5mm以下），粘膜内癌および進行癌を対象として①細胞水準で正常細胞に類似を求める，②組織水準で癌発生の場である粘膜の性状と癌組織型との関係，の2点について光顕的・電顕的ならびに統計的に解析を行ない，“分化型癌（乳頭管状腺癌・管状腺癌）は胃の腸上皮化生粘膜を，一方，未分化型癌（粘液細胞性腺癌・硬癌）は胃固有粘膜を発生母地とする”との胃癌組織発生についての一つの概念を得た．

　この概念は，おもに胃幽門前庭部に発生した癌を対象として導かれたものである．ということは胃幽門前庭部は胃癌の好発部位⁴⁾であり，多数の胃癌をあつかう場合にはその大部分が幽門前庭部に発生した癌で占められるからである．

　Histogenesis of cancer in the upper segment of the stomach has been investigated by defining it as the cardiac half of the stomach mostly formed by the mucosa of the fundic glands. The subjects of this study are 279 cases of gastric resection most of which have been histologically examined, including 220 cases of gastric cancer. The majority of these cases show early phase in development.

　In order to assume the relationship between histological types of cancer grown up to certain dimensions and the condition of the mucosa at the time of its development, tendency of changes of the gastric mucosa including age must he grasped since the gastric mucosa is not stationary.

　In the study of 279 cases in these changes of the intermediate zone and of the grade of intestinal metaplasia, the following conclusion has been drawn : Generally speaking, the irreversible shifting of the intermediate zone takes place as the age advances and the rate of intestinal metaplasia becomes accordingly more severe.

　Taking this mucosal vicissitude into consideration, we have investigated cancer of the stomach located in its upper segment. It was found as a result that cancer lesions in 22 cases were encircled all around by the mucosa of the fundic glands, and belonged histologically all to undifferentiated cancer (mucocellulare and scirrhus adenocarcinomas). Since the shifting of the intermediate zone is irreversible and intestinalized epitheliums scarcely present in the fundic glands mucosa, it can be assumed that the mucosa at the site of cancer lesion was still that of the fundic glands at the time of cancer development in these 22 cases. In other words, because the fundic glands together with the pyloric ones belong to the mucosa proper to the stomach, cancers of the undifferentiated type arise from the proper mucosa of the stomach.

　Meanwhile, there were 7 cases of cancer lesions in the upper gastric segment that were away from the intermediate zone and situated in the intestinalized mucosa. They were all differentiated cancer (tubular and papillotubular adenocarcinomas).

　Histogenesis of cancer in the upper segment of the stomach is also compatible with our concept of cancer genesis elsewhere already reported.