Benign Ovarian Surface Epithelial-Stromal Tumor (EFO_1000117, an Experimental Factor Ontology term) is a non-metastasizing neoplasm that originates from the surface epithelium of the ovary. It is composed of epithelial cells and stroma. Representative examples include serous cystadenoma, mucinous cystadenoma, clear cell adenofibroma, and benign Brenner tumor.