US - complex, multi-septated, predominantly cystic mass extending from the pelvis into the upper abdomen with increased flow within the solid components on Colour Doppler. This most likely represents an ovarian tumor. There is also a moderate amount of ascites.

CT scan (one day later) - complex mass arising from the left ovary and a moderate amount of ascites.

There are four major categories of ovarian tumors:
1. Epithelial tumors (65-75%) - serous or mucinous cystadenoma/carcinoma, clear cell carcinoma, Brenner tumor
2. Germ cell tumors (15%) - dysgerminoma, embryonal cell cancer, choriocarcinoma, teratoma
3. Sex-chord-stromal tumors (5-10%) - granulosa cell tumor, thecoma, fibroma
4. Metastatic tumors (10%) - uterine, stomach, colon, breast, lymphoma

Mucinous cystadenomas make up 15-20% of all ovarian tumors. They often become very large and can extend up into the abdomen. Pseudomyxoma peritonei can result if the tumor ruptures and spills its contents into the abdomen.

These tumors are usually evaluated using ultrasound, CT scan, or MRI. Findings on imaging studies are nonspecific. These ovanian tumors are usually multi-septated, cystic masses with thin walls. They also contain varying amounts of solid tissue which consists of proliferating stromal tissue, papillae, or malignant tumor cells.

Mucinous cystadenomas are divided into three categories: benign, borderline, and malignant. Survival is largely dependent on the histology of the tumor, with a 10 year survival rate of 100% for benign tumors, 60% for borderline tumors, and only 34% for the malignant subtype. There is some difference in ages of the peak incidence for the different subtypes with considerable overlap as described below. In general, benign tumors tend to present earlier, while malignant tumors are often seen later in life.

Benign mucinous cystadenomas comprise 80% of mucinous ovarian tumors and 20-25% of benign ovarian tumors overall. The peak incidence occurs between 30-50 years of age. Benign tumors are bilateral in 5-10% of cases.

Borderline mucinous cystadenomas make up about 10% of mucinous ovarian neoplasms and are bilateral in 10% of cases.

Malignant mucinous cystadenoms are rare, and encompass 10% of mucinous ovarian tumors and 5-10% of primary malignant ovarian neoplasms overall. They are bilateral in 15-30% of cases and have a peak incidence between 40-70 years of age.