FINAL DIAGNOSIS: VASCULAR ADRENAL CYST
Adrenal cysts are uncommon lesions that have conventionally been divided into epithelial, parasitic and vascular types. Vascular adrenal cysts are by far the most common type and have been traditionally subdivided into endothelial and hemorrhagic (pseudocystic) variants. Although they have some different histologic features, recent studies showed that the two entities might represent a spectrum of vascular adrenal lesions.
Vascular adrenal cysts vary greatly in size from microscopic to more than 50 cm in diameter and may contain up to 11 liters of fluid. There is no predilection for the right or left gland and the reported bilaterality is 8%. All age groups are affected; the highest incidence is in the 5th and 6th decades. There is a 2:1 female predominance. Symptoms that derive from vascular adrenal cysts are usually associated with large cysts, presumably due to compression of surrounding viscera, and include pain and vague gastrointestinal complaints. Smaller cysts are usually incidentally found during the evaluation of unrelated abdominal conditions.
Hemorrhagic (pseudocystic) cysts consist of a hyalinized fibrous capsule containing nests of entrapped adrenal cortical cells and amorphous cyst contents composed of a mixture of serum, blood and fibrin. Dilated, thin walled vascular channels lined by flattened cells are usually present within the fibrous capsule and the adjacent adrenal gland. The endothelial variant is composed of a fibrous wall focally lined on its inner aspect by flattened cells resembling normal endothelium. The lining of endothelial cysts stains intensively for collagen type IV but shows only focal, weak staining for Factor VIII-related antigen. In contrast, the vascular channels of the hemorrhagic cysts are strongly positive for FVIII-RA, collagen type IV, U. europaeus agglutinin I lectin, CD34, and laminin. These histologic and immunohistochemical findings strongly suggest a vascular origin for these lesions. The endothelial variant of adrenal vascular cyst is slightly more common than the hemorrhagic variant and is thought to arise from a preexisting vascular hamartoma of blood vessel or lymphatic nature. Some authors have proposed that hemorrhagic cysts result from intraadrenal hemorrhage, whereas others argue that they are closely related to endothelial cysts. Hemorrhagic cysts can occur as a component of the Beckwith-Wiedemann syndrome.
Clinically, the differential diagnosis of vascular adrenal cysts is extensive and includes any lesion that can present as an upper abdominal mass. This includes adrenal neoplasms; hepatic cysts and hemangiomas; cystic renal cortical adenomas and carcinomas; Wilms' tumor; pancreatic, mesenteric and urachal cysts; retroperitoneal tumors; polycystic kidneys; and hydronephrosis.
The pathologic differential diagnosis includes parasitic cysts ( hydatid cysts) and epithelial cysts. The latter are lined by a single layer of cytokeratin positive cells and have been subdivided into three groups based upon proposed theories of pathogenesis: retention cysts, embryonal cysts and cysts arising within adrenal cortical adenomas. A potential diagnostic pitfall would be confusing a vascular hemorrhagic cyst with a cystic or degenerating adrenal cortical neoplasm, either benign or malignant. A cortical neoplasm can be ruled out by noting the absence of autonomous hormone production, atrophy of the adjacent cortex, the normal appearance of cortical cell islands, a rich intracapsular vascular network and thrombotic material rather than necrotic tumor cells.
Surgical excision is indicated in the presence of symptoms, endocrine abnormalities (even when subclinical), complications, suspicion of malignancy and/or large size (>5cm).
Contributed by Manuel Suarez, MD and Sheldon Bastacky, MD