P53 PROTEIN EXPRESSION AND DNA-PLOIDY IN CYSTIC TUMORS OF THE PANCREAS

Cystic tumors of the pancreas form a heterogeneous group, with benign, premalignant, and malignant tumors. The molecular events that underli e their neoplastic transformation process are poorly understood. Our p urpose was to study DNA ploidy by flow cytometry and p53 protein expre ssion by immunohistochemistry in a large series of cystic tumors of th e pancreas, The series of 51 surgical specimens included 18 serous cys tadenomas, = 20 mucinous cystic tumors (benign, n = 14; borderline, n 1; malignant, n = 5), 10 intraductal papillary-mucinous tumors (benign , n = 4; borderline, n = I; malignant, n = 5), and 3 papillary and cys tic tumors. The p53 protein immunohistochemical study was done in all cases on deparaffinized sections stained with the monoclonal antibody DO7. DNA flow cytometry was performed in 31 cases on formalin-fixed an d paraffin-embedded material, Neither p53 protein immunoreactivity nor DNA aneuploidy was observed in any case of serous cystadenoma. p53 pr otein overexpression was present in four of five malignant mucinous cy stic tumors but was absent in benign and borderline cases. Only one ca se of malignant mucinous cystic tumor was DNA aneuploid. All benign an d borderline intraductal papillary-mucinous tumors were p53 negative, and two of five malignant cases were p53 positive. There was no DNA an euploidy in any case of intraductal papillary-mucinous tumors. The thr ee cases of papillary-cystic tumors showed neither p53 protein immunor eactivity nor DNA aneuploidy. In cystic tumors of the pancreas, p53 pr otein overexpression and DNA aneuploidy are rare events, restricted to malignant cases, mostly mucinous cystadenocarcinomas. Our results con firm that this group of tumors is heterogeneous and underline the need for earlier markers of an aggressive behavior.