A malignant serous cystic epithelial neoplasm arising from the ovary. It is characterized by the presence of glandular, papillary, or solid structures. Psammoma bodies may be present. In well differentiated cases the malignant epithelial cells resemble the cells of fallopian tube epithelium. In poorly differentiated cases the malignant epithelial cells show anaplastic features. [from NCI]