Cell kinetics, p53 and bcl-2 expression, and c-Ki-ras mutations in flat-elevated tubulovillous adenomas and adenocarcinomas of the colorectum: Comparison with polypoid lesions

Background: Flat(-elevated) tubulovillous adenomas and adenocarcinomas of t he colorectum constitute a specific type of neoplasm with superficial sprea ding growth. To establish their characteristics, a comparative investigatio n of a series of tumors was performed. Methods: A total of 56 Bat tubulovil lous tumors (39 adenomas, 17 invasive carcinomas) and 154 polypoid tubular or villous tumors (77 adenomas, 77 invasive carcinomas) were comparatively assessed for cell kinetics and molecular alterations. Results: Ki-67 labeli ng and p53 expression for both types of tumors increased along with degree of dysplasia or invasion, whereas bcl-2 expression showed an inverse decrea se. However, apoptotic activity was invariably low in the flat tubulovillou s tumors, as compared with the polypoid tumors, in which increase was appar ent with tumor progression. The flat tubulovillous tumors also showed a hig her frequency of c-Ki-ras mutations (92.9%) than the polypoid tubular tumor s (40.0%). Conclusions: The flat tubulovillous tumor can be considered a di stinct entity, with characteristics different from the polypoid counterpart .