Comparative clinicopathological and cytomorphological analyses of peritoneal carcinomatosis associated with metastatic breast carcinoma and primary peritoneal/ovarian carcinoma in patients with a history of breast carcinoma.

Causes of peritoneal carcinomatosis (PC) in patients with a history of breast carcinoma include both metastatic breast carcinoma (MBC) and primary peritoneal/ovarian carcinoma (PPOC). The origin of PC is important to determine the appropriate treatment strategy. Cytological examination of the peritoneal fluid (PF), which may be the first diagnostic approach to PC, is of distinct value in confirming the presence of malignant cells and determining the origin of PC. We analyzed the clinicopathological and cytomorphological characteristics of 33 patients with a history of breast carcinoma whose PF cytology contained malignant cells. Cases showing positive immunoreactivity for PAX8 and a lack of GATA3 expression were considered as PPOC. Sixteen patients developed PC caused by PPOC. PPOC patients were characterized by early-stage primary breast carcinoma, absence of non-peritoneal MBC before PC, and normal serum levels of CEA and CA15-3. Fourteen PPOC patients had pathogenic germline BRCA mutations. Cytological examination revealed that most of the PPOC cases had a dominant papillary arrangement of the tumor cells with severe nuclear pleomorphism, occasional bizarre nuclei, and atypical mitotic figures. Patients with PPOC who underwent cytoreductive surgery had a significantly longer survival time compared to those who did not, or MBC patients. In patients with a history of breast carcinoma presenting with PC, the presence of early-stage primary breast carcinoma, no prior non-peritoneal MBC, and a dominant papillary cellular arrangement pattern in the PF cytology were independent predictors of PPOC. Cytoreductive surgery significantly improved survival for patients with PPOC.