An epithelial-stromal cystic tumor containing serous fluid

Serous cystadenomas are the most common type of epithelial-stromal tumors. They are lined with cells similar to those lining the fallopian tubes, suggesting that the origin may be tubal rather than ovarian. These cysts can become very large, although not typically as large as mucinous cystadenomas, and up to 20% are bilateral. Most (70%) are benign, whereas 5% to 10% have borderline malignant potential, and 20% to 25% are frankly malignant, although there is no indication that benign serous tumors transform into malignant ones.

Serous cystadenomas are typically thin-walled unilocular cysts, although they can also be multilocular. They are filled with serous fluid, which is usually clear or may contain tiny particles. Although less common, a borderline or malignant tumor must be considered (see elsewhere in the book for more information on borderline and malignant ovarian tumors) in cysts with solid components or nodules, especially if blood flow is detected with color Doppler.