Adenoma and tiny carcinoma in adenoma of the papilla of Vater--p53 and PCNA.

BACKGROUND/AIMS: Adenomas develop only rarely in the small bowel mucosa. We particularly tried to clarify the histologic change in atypia of ampullary adenomas which are not familial polyposis.

METHODOLOGY: Four adenomas, 4 adenocarcinomas, and 4 normal mucosal regions of the ampulla of Vater were investigated in this study. All cases were characterized in paraffin sections for the presence of p53 protein using the anti-p53 monoclonal antibody (DO7, Dako Corp., Glostrup, Denmark) and proliferating cell nuclear antigen using the anti-PCNA antibody (PC 10, Dako A/S, Copenhagen, Denmark). To obtain the percentages (labeling index) of PCNA, a dual wavelength imaging microdensitometer (CAS 200, Elmhurst, IL) was used.

RESULTS

Transition of adenoma into adenocarcinoma was recognized in 2 of 4 cases. Labeling index of PCNA was 12.2% in normal mucosa, 41.3% in adenomas, and 66.0% in adenocarcinoma, respectively. In 2 cases with carcinoma in adenoma, labeling index was higher in carcinomatous lesion than in adenomatous lesion. p53 Protein was positive in all cases of adenocarcinoma of the ampulla of Vater, and not in any case of normal mucosa or adenoma.

CONCLUSIONS

The adenoma-carcinoma sequence was morphologically recognized especially in tiny carcinoma in adenoma of the papilla of Vater. Both p53 mutation and high proliferative activity play important roles for the histogenesis of invasive adenocarcinoma.