Morphological events found at the invading edge of colorectal carcinomas in baboons

Background: Earlier studies at the growing edge of colorectal cancer (CRC) in humans and rats have shown dilated neoplastic glands, some with a thin layer of flattened tumor cells (FTCs), some lacking one or more groups of consecutive lining tumor cells (called glandular pores, GPs). Materials and Methods: The characteristics of the neoplastic glands at the invading edge of CRCs were investigated in 39 baboons. A total of 190 neoplastic glands were studied in the 38 cases of glandular-forming adenocarcinomas. Results: In the studied neoplastic glands FTCs or GPs were recorded in 44.7% (85 glands). FTCs were found in 9.5% (18 glands) and GPs in 35.3% (67 glands). Only 7.9% or 3 out of the 38 animals showed neoplastic glands with GPs in the bulk of the tumor. Conclusion: In similarity to colorectal adenocarcinomas in humans, flattened tumor cells and glandular pores were found at the invading tumor edge of colorectal adenocarcinomas in baboons. A possible mechanism of host invasion is proposed.