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 serou s 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 overexpres sion of HER-2/neu and p53 protein. Of the PPSPCs, 53.8% were poorly differe ntiated, 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 significan t increase in the expression of Ki-67 was found in PPSPCs (37.7%) versus OS PCs (26.8%) (p=0.039). The same trend was found for HER-2/neu, being overex pressed in 38.5% of the PPSPC versus 9.1% of the OSPCs (p=0.019). Overexpre ssion of p53 was found in 30.8% of the PPSPCs and 45.4% of the OSPCs (not s ignificant). 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 significant ly different immunohistochemical expression of ER, PR, Ki-67, and HER-2 in PPSPCs compared with OSPCs suggests that different molecular events may lea d to tumorigenesis in these two cancers.