The possibility of nonpolypoid carcinogenesis in the large intestine as inferred from frequencies of DNA aneuploidy of polypoid and crater-shaped carcinomas.

DNA ploidy patterns were studied by cytofluorometry in 60 cases of crater-shaped invasive carcinoma and 30 cases of polypoid tumor (severe dysplasia or submucosally invasive carcinoma located in the pedunculated, semipedunculated, or sessile polyp) of the large intestine. The data were compared with 20 cases of intramucosal differentiated (or intestinal type) adenocarcinoma of the stomach, with special reference to their macroscopic shape and frequency of DNA aneuploidy. DNA aneuploidy was found in 77% of the crater-shaped carcinomas and in 17% of the polypoid tumors of the large intestine. The frequencies were significantly different and the frequency gap amounted to 60%. However, 18 of 20 (90%) gastric adenocarcinomas were nonpolypoid in shape, whereas two (10%) were polypoid. DNA aneuploidy was found in 50% of the gastric adenocarcinomas and 56% of the nonpolypoid gastric adenocarcinomas. This value did not differ from the values reported previously for the submucosally invasive and advanced crater-shaped intestinal type adenocarcinomas of the stomach. Biologic characteristics of adenocarcinomas of the large intestine can be compared with those of intestinal type adenocarcinomas of the stomach, because intestinal type gastric adenocarcinoma is surrounded mostly by intestinalized mucosa and considered to arise from the epithelium under induction or progression of intestinal differentiation. Therefore, we inferred that the frequency gap in DNA aneuploidy between the crater-shaped and polypoid tumors of the large intestine implies that in the large intestine approximately 60% of the crater-shaped invasive carcinomas develop from the small nonpolypoid carcinomas.