It is often difficult to confidently ascertain the origin of large masses, as in this case. Differential diagnoses to consider includes an ovarian cyst (no clear plane with the ovaries), a mesenteric or omental cyst, or a duplication cyst.

Intraoperatively, this large cystic mass was found to be arising from the left ovary.

Histopathology

Macroscopic description: The specimen consists of collapsed cystic tissue with an ovary seen within the cyst. Omental specimen containing yellowish tissue.

Microscopic description: Sections of the cyst show ovarian and fibro-collagenous stroma lined by stratified ciliated columnar epithelium forming broad branching papillae. No marked cellular atypia or stromal invasion was seen. Fallopian tubes are unremarkable. Omental specimens showed sheets of congested mature adipocytes with focal lymphoid aggregates. No malignancy was seen.

Diagnosis: Serous cystadenoma of the ovary. No malignancy was seen.