Histopathogenesis of Carcinoma Induced in the Glandular Stomach of C57BL Mice by the Intramural Injection of 20-Methylcholanthrene

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Abstract
A single dose of 0.3 mg. of 20-methylcholanthrene in on aqueous Methocel suspension was injected intramurally into the submucosa of the glandular stomach of 109 (effective number 108) strain C57BL mice. The experiment lasted 175 days. During this time mice were killed at regular intervals to afford material for a study of the histopathogenesis of carcinoma of the glandular stomach. Twenty-four of 50 mice killed in the effective tumor period had malignant gastric tumor with a carcinomatous element. Adenocarcinoma of the glandular stomach was diagnosed in a mouse killed on the 42nd day post injection and in 21 other mice necropsied between the 56th and 175th day. In addition, there was 1 mixed adenocarcinoma and sarcoma, 1 mixed adenoacanthoma and sarcoma, and 1 sarcoma. The results of this experiment compared with those of a somewhat similar but longer term experiment revealed a larger number of carcinomas in the present experiment. A possible explanation is that gastric neoplasms may fail to progress or may even regress after loss of methylcholanthrene from the site of injection in the wall of the stomach. As in experimental carcinomas of the forestomach and the small intestine, the histopathogenesis of induced carcinoma of the glandular stomach is a complicated process, participated in by the glandular mucous membrane of the stomach, the stroma, blood vessels, and muscularis. The experimental carcinomas of the glandular stomach appear to develop from multicentric neoplastic foci and to originate from the deep mucosa in association with umbilicate lesions.