Immunohistochemical evidence for the vascular origin of primary adrenal pseudocysts.

Pseudocysts are the most common nonfunctioning cystic adrenal lesions associated with symptoms. We have studied tissue from two patients with large adrenal pseudocysts in whom no antecedent cause could be documented. Immunohistochemical examination of these formaldehyde-fixed paraffin-embedded tissues with antibodies directed against the major proteins of the basement membrane (laminin and type IV collagen) revealed intense linear staining surrounding the cystic spaces and at the compressed adrenal cortical/pseudocyst interface. These findings lead us to conclude that these lesions are vascular in nature and, therefore, closely related to the previously recognized adrenal cysts of endothelial origin.