High-grade and low-grade pelvic serous neoplasms demonstrate differential p53 immunoreactivity in peritoneal washings

Serous neoplasms of the female pelvis share a müllerian phenotype. Unlike low-grade serous neoplasms (LGSNs), high-grade serous carcinomas (HGSCs) commonly display p53 mutations. The current study correlates p53 immunoreactivity in peritoneal washings with the cytologic interpretation and histology of the corresponding serous neoplasm.

Peritoneal washings from consecutive cases of pelvic serous neoplasms were identified (n=45, 31 HGSCs and 14 LGSNs), with a control population selected from benign resections. Immunoreactivity for p53 was scored as a percentage of positive epithelioid cells by blinded manual cell count.

Washings from LGSNs and HGSCs were cytomorphologically positive with similar frequency (57 vs. 77%, respectively, p=0.15, Fisher's exact test). Immunoreactivity for p53 was not predictive of morphologic positivity. The percentage of p53-positive cells was higher in HGSCs (47±42%), compared to LGSNs (9±9%) and negative controls (2±2%, n=10). The difference in p53 immunoreactivity was statistically significant (p<0.00009, ANOVA).

The proportion of p53 immunoreactive cells was higher in cases of HGSCs, reflecting the importance of p53 mutations in high-grade serous tumorigenesis. The presence of p53 staining is not diagnostic for neoplastic cells; however, peritoneal washings are potential specimens in the investigation of serous neoplasia.