Mucinous tumours are part of the surface epithelial-stromal tumour group of ovarian neoplasms, and account for 12-15% of all ovarian tumours. Approximately 75% are benign, 10% are borderline and 15% are malignant. Rarely, the tumour is seen bilaterally, though this is uncommon.

Benign mucinous tumours are typically multilocular (have several lobes), and the cysts have a smooth lining of epithelium that resembles endocervical epithelial cells with small numbers of gastrointestinal-type epithelial cells. Borderline and malignant mucinous tumours often have papillae and solid areas. There may also be hemorrhage and necrosis. It is well-documented that malignancy may be only focally present in mucinous neoplasms of the ovary, so thorough sampling is imperative. The microscopic pathological appearances of borderline and carcinomatous mucinous tumours are quite variable and there is some uncertainty and controversy about diagnostic criteria.