Which ovarian tumor is typically benign and can be bilateral?

The serous cystadenoma is typically a benign ovarian tumor that can be bilateral, making it a common finding during the evaluation of adnexal masses. These tumors are usually cystic and filled with a clear, serous fluid. While bilaterality is less common overall in ovarian tumors, serous cystadenomas are known for this characteristic, particularly in familial cases or when they are associated with certain syndromes, such as BRCA mutations.

Being relatively common benign tumors, serous cystadenomas are frequently discovered incidentally during imaging or surgical procedures. They are characterized histologically by a single layer of tall columnar epithelial cells and may have areas of papillary growth, but this does not change their benign nature. In contrast, the other options listed represent malignancies (such as endometrioid carcinoma and clear cell carcinoma) or tumors that are generally not associated with bilaterality as frequently as serous cystadenomas. Mucinous cystadenomas can also be bilateral, but they are more uncommon than serous cystadenomas. Thus, the characteristics of serous cystadenoma align with the question's criteria regarding benignity and bilaterality.