Multifocal extraovarian serous carcinoma. A histochemical and immunohistochemical study.

Three cases of multifocal extraovarian serous carcinoma are presented. This rare, interesting tumor is characterized by a peritoneal carcinosis with ascites and by a histological pattern similar to one of the ovarian serous carcinoma without primary involvement of the ovaries. The pathological criteria for a differential diagnosis between this condition and a localization of ovarian carcinoma are discussed. Histochemical studies show the presence of mucins and the absence of ialuronic acid in the neoplastic cells. The positivity to the low molecular weight cytokeratins is strong in the normal mesothelial cells, and weak in the hyperplastic and neoplastic cells. The meaning of these findings in the tumoral histogenesis is discussed.