Pathology of borderline and invasive cancers.

Epithelial ovarian tumors are heterogeneous neoplasms primarily classified according to cell type. They are further subdivided into benign, borderline, and malignant (carcinomas), and this subdivision is very important as it correlates with behavior. Borderline ovarian tumors show epithelial proliferation higher than that seen in their benign counterparts and variable nuclear atypia; however, in contrast to carcinomas, there is no destructive stromal invasion, and their prognosis is much better. Ovarian carcinomas are the most common ovarian cancers and the most lethal gynecological malignancies. On the basis of histopathology and molecular genetics, they are divided into five types (high-grade serous (70%), endometrioid (10%), clear cell (10%), mucinous (3%), and low-grade serous carcinomas (<5%)), which are morphologically diverse and account for over 95% of cases. These tumors are essentially distinct diseases, as indicated by differences in epidemiological and genetic risk factors, precursor lesions, patterns of spread, molecular alterations, response to chemotherapy, and prognosis. For a successful specific treatment, reproducible histopathological diagnosis of the tumor cell type is critical.