Vast majority of mucinous carcinomas are confined to the ovary (Stage I) and are treated by abdominal exploration, unilateral salpingo-oophorectomy (given the low frequency of bilaterality), and staging biopsies. A coexisting mucinous neoplasm in the appendix must be excluded, especially if the tumor is bilateral or if there is pseudomyxoma peritonei. Appendectomy is performed in some cases. A prolonged follow-up is necessary to exclude the development of tumor in the contralateral ovary. The image shows mucinous carcinoma with destructive stromal invasion. The invasive foci are composed of distorted glands, isolated tumor cells, and small nests or clusters of cells with high-grade nuclear features that are haphazardly infiltrating desmoplastic stroma.