Mucinous carcinomas of the ovary make up 3-4% of all primary ovarian carcinomas. The mean age at diagnosis is around 45 years. Most patients present with an abdominal mass, pain and abdominal distension. The disease is usually confined to the ovary (Stage I) at the time of presentation. Only rare cases present at advanced stages. GROSS: Mucinous carcinomas of ovary are usually large, unilateral (<5% are bilateral), unilocular or multilocular cystic masses filled with viscous mucinous fluid. They have smooth external surface although adhesions may be present. They usually have solid and papillary areas that may either be soft and friable or firm with hemorrhagic and necrotic foci. Grossly, it is not possible to reliably separate mucinous borderline tumors from carcinomas. Extensive sample of ovarian mucinous tumors is essential because benign, borderline, and malignant foci coexist, often next to each other, and the invasive component may be present in only a small portion of the tumor. The image shows a 13-cm mucinous cystadenocarcinoma involving the right ovary in a 74-year-old lady. There was a microscopic metastasis in the other ovary, and the peritoneal washings were positive. Image courtesy of: Ed Uthman, MD, Houston, Texas.