Histopathology of ovarian epithelial tumors. A, high-grade serous carcinoma is composed of a solid mass of cells with slit-like spaces. Nuclei are large, hyperchromatic, and pleomorphic with high mitotic activity (>12 mitoses per 10 high-power fields) (HES ×100). B, low-grade serous carcinoma is composed of micro- or macropapillae lined by uniform small cells with limited nuclear pleomorphisms and low mitotic activity (<12 mitoses per 10 high-power fields), associated with psammoma bodies (HES ×100). C, endometrioid carcinoma is arranged in a cribriform pattern lined by cuboidal cells with eosinophilic cytoplasm and moderate nuclear atypia (HES ×200). D, the expansile pattern of mucinous carcinoma shows proliferation of complex glands arranged back to back with limited intervening stroma, exhibiting moderate cytologic atypia (HES ×200). E, destructive pattern of mucinous carcinoma shows proliferation of irregular glands, nests, and cells with malignant cytology, infiltrating ovarian stroma (HES ×200). F, clear cell carcinoma shows papillae lined by cuboidal, hobnail cells with clear or eosinophilic cytoplasm and atypical nuclei. The papillae are round and small with a dense hyaline basement membrane material forming the core of the papillary stalk (HES ×200).