Adrenal pseudocysts: Evidence of their posthemorrhagic nature

Hemorrhagic adrenal pseudocysts are uncommon nonneoplastic lesions that hav e been reported as secondary to intraparenchymal hemorrhage or alternativel y related to endothelial (vascular) cysts. Ultrastructural and immunohistoc hemical evidence in support of the latter has been presented, but the exact nature of hemorrhagic adrenal pseudocysts remains poorly defined. We evalu ated six surgical specimens of hemorrhagic adrenal pseudocysts using immuno histochemical staining for CD31 and CD34, as well as conventional histochem istry. All six cases had hemorrhagic contents within a wall of variable thi ckness possessing focal areas of linear, disrupted elastin, and smooth musc le, Three cases demonstrated extensive thrombosis with organization, includ ing papillary endothelia I hyperplasia, simulating angiosarcoma. In these c ases, CD31 and CD34 staining decorated areas of papillary endothelial hyper plasia as well as foci of the internal cyst lining, whereas the other cases were negative for both antibodies. Of interest is the history of FNA prior to surgical resection in three cases of hemorrhagic adrenal pseudocysts, t wo of which showed papillary endothelial hyperplasia. The presence of papil lary endothelial hyperplasia and our immunohistochemical findings support t he conclusion that adrenal pseudocysts are posthemorrhagic and derive from vascular disruption. Furthermore, FNA or other interventional studies may b e associated with papillary endothelial hyperplasia in hemorrhagic adrenal pseudocysts.