Answer: Adrenal pseudocyst

Histology: The lesion is composed of a cyst with a fibrous wall that abuts on the adrenal cortex. In some areas dystrophic calcification is present. In some areas of the wall numerous small vascular channels were present and there were foci of smooth muscle scattered through the wall, suggesting origin associated with a venous structure.

Discussion: A variety of cystic lesions occur in or adjacent to the adrenal gland. An adrenal cyst can be clinically confused with renal or retroperitoneal neoplasm because of large size and the presence of calcification. Several types of adrenal cyst are recognized and they may, in fact, be related. One type is known as a “vascular” cyst. It contains serous fluid, is often multilobulated, and has a demonstrable endothelial lining. Adrenal cortex may be present in the wall. The other type of cyst, represented by our case, is a hemorrhagic cyst or pseudocyst. This lesion contains clotted blood, hyalinized thrombus and attached adrenal cortex. No endothelial lining can be demonstrated. It has been suggested that both types arise on the basis of a vascular anomaly, either lymphatic or of blood vessel origin. Hemorrhagic cyst may occur as a component of the Beckwith-Wiedemann syndrome.

Other cystic lesions that occur in the adrenal include bronchogenic cysts, lined by respiratory epithelium, and even extralobar pulmonary sequestrations. As in the spleen, rare cases of true epithelial-lined adrenal cysts have been reported. Their histogenesis may be similar to that of the related splenic cysts. It may be derived from mesothelial structures. In the case shown here, the lesion was clinically not attached to the kidney at the time of surgery. Some renal cell carcinomas, however, may present in a similar fashion with a cystic wall in which epithelium may be found only after the entire specimen is examined.