Monarch Disease Ontology id MONDO_0024885 (malignant ovarian serous tumor) is an invasive malignant neoplasm that arises from the ovary and is characterized by the presence of malignant epithelial cells that, in well differentiated tumors, resemble the epithelium of the fallopian tube or, in poorly differentiated tumors, show anaplastic features and marked nuclear atypia. It includes serous adenocarcinoma and serous adenocarcinofibroma. Also known as: ovarian serous tumor, malignant.