Immunohistochemical comparison of primary peritoneal and primary ovarian serous papillary carcinoma.

Twenty-six patients, meeting strict criteria for primary peritoneal serous papillary carcinoma (PPSPC), were matched to 22 patients with ovarian serous papillary cancer (OSPC) for age and stage. Immunohistochemistry was used to determine the status of estrogen receptors (ER), progesterone receptors (PR), the expression of cell proliferation marker Ki-67, and the overexpression of HER-2/neu and p53 protein. Of the PPSPCs, 53.8% were poorly differentiated, as were 18.2% of the OSPCs (p = 0.012). Positive immunostaining for ER and PR was less in PPSPCs (30.8% and 46.2%, respectively) than OSPCs (72.7% and 90.9%; p = 0.003 and p = 0.001, respectively). Conversely, a significant increase in the expression of Ki-67 was found in PPSPCs (37.7%) versus OSPCs (26.8%) (p = 0.039). The same trend was found for HER-2/neu, being overexpressed in 38.5% of the PPSPC versus 9.1% of the OSPCs (p = 0.019). Overexpression of p53 was found in 30.8% of the PPSPCs and 45.4% of the OSPCs (not significant). There was a significantly worse survival rate for PPSPCs than for OSPCs (p = 0.017), yet none of the studied parameters were significantly correlated with survival within the PPSPC and OSPC groups. The significantly different immunohistochemical expression of ER, PR, Ki-67, and HER-2 in PPSPCs compared with OSPCs suggests that different molecular events may lead to tumorigenesis in these two cancers.