Mesothelial cyst of the adrenal gland.

A case of mesothelium-lined cyst of the adrenal gland is reported. Although more than 300 adrenal cysts have been reported in the literature, epithelial cell-lined cysts are rare and comprise only 9% of the cases. An adrenal cyst was found, the lining cells of which had features consistent with mesothelial cells. The inner surface of the cyst was lined by a single layer of cuboidal cells, which showed alcian blue positive cellular outline. Immunohistochemically, the lining cells were positively stained for keratin, epithelial membrane antigen and CA-125. Electron microscopic examination revealed many long complex microvilli and desmosomes in the lining cells. There was a basal lamina beneath the cell layer. These morphological and immunohistochemical findings indicated that the lining cell is derived from mesothelium.