Expression of p53 protein in invasive colorectal carcinomas of different histologic types.

BACKGROUND. This study was performed to determine whether morphologic differences of colonic cancer types can be related to different genotypes of these tumors. METHODS. Paraffin sections of 76 human invasive colorectal carcinomas were examined for the overexpression of p53 oncoprotein with the avidin-biotin complex-peroxidase staining procedure and CM-1 antiserum, which detects p53 protein in paraffin-embedded material. The tumors were categorized as mucinous (22 cases), most of which originated from adenomas, and nonmucinous, which were subdivided into carcinomas originating from adenoma-carcinoma sequence (ACS) (29 cases) and de novo (DN) carcinomas (25 cases). RESULTS. Nineteen DN carcinomas (76%), 21 ACS carcinomas (72%), and 8 mucinous carcinomas (36%) exhibited detectable amounts of p53 protein in the tumor cell nuclei. Strong overexpression of p53 protein coincided with a high percentage (> 40%) of stained nuclei in 40% of ACS and 48% of DN carcinomas versus 9% of mucinous tumors. The percentage of stained nuclei, intensity of staining, and distribution of the stained areas did not correlate with the grade of differentiation or the invasive edge of the tumors. Along with nuclear staining of the tumor area, a distinct perinuclear staining of normal epithelial cells adjacent to the tumor was observed in 48% of DN, 7% of ACS, and 9% of mucinous carcinomas. CONCLUSIONS. The current results, in combination with the recently published data on Ki-ras and c-myc alterations, indicate that mucinous carcinomas differ from nonmucinous colorectal carcinomas in their genetic lesions.