Giant Primary Retroperitoneal Serous Cystadenoma: A Rare Entity Mimicking Multiple Neoplastic and Nonneoplastic Processes.

Serous cystadenoma, often known as ovarian serous cystadenoma, is one of the common benign ovarian neoplasms. On the other hand, primary retroperitoneal serous cystadenoma is an extremely rare benign entity whose pathogenesis has not been well understood. Clinical presentation and symptomatology vary greatly and are highly dependent on the size and location of the lesion. Primary retroperitoneal serous cystadenomas are homogeneous, unilocular, thin-walled cystic masses. If they grow large enough, they tend to compress and deform adjacent organs, giving clinicians a misimpression of malignant pattern of behavior. Therefore, it is crucial to differentiate benign primary retroperitoneal serous cystadenomas from other epithelial and nonepithelial cystic lesions or masses involving retroperitoneal regions. Management-wise, complete cyst excision without rupture or spillage of the cyst contents is the recommended therapeutic method for primary retroperitoneal serous cystadenomas. This review will highlight the current knowledge on its pathogenesis and discuss its histopathologic features and differential diagnoses from the pathologist's point of view.