Many ovarian epithelial tumors show admixture of two or more histologic subtypes within the same tumor. This is not surprising since many of them have common Mullerian origin. The minor histologic component should be grossly recognizable or account for at least 10% of the tumor microscopically. Almost all combinations of epithelial tumors have been recognized in the ovaries. Endometrioid tumors with squamous differentiation and neuroendocrine tumors with another epithelial tumor component are excluded from this group. About 25% of Brenner tumors are associated with other ovarian epithelial tumors, most commonly the mucinous type. This photograph shows an incidentally found benign Brenner tumor (solid yellow nodule) with mucinous cystadenoma (cystic space below) in an ovary removed with a hysterectomy specimen. Image courtesy of: Steven O'Connor, MD, Houston, Texas, USA. Used with permission.