Large cholesterol granuloma cysts in the mastoid. Clinical and histopathologic findings.

Large cholesterol cysts were found in revision surgery in six patients with previous ear surgery one to 28 years ago. The cysts mimicked brain herniation in open cavities, filled the mastoid and ear canal in closed cavities, or caused postauricular swelling. Bone around the cysts was soft and granulomatous. Secretory cells were scarce in the epithelial lining of the lumen, but subepithelial glands were frequent. Cholesterol granulomas and hemosiderin-laden macrophages were present inside the wall. The cyst lining and the glands under it showed cytokeratin staining typical for simple and glandular epithelia. Antiprekeratin antibodies showed no decoration of the lining but reacted positively with the meatal skin. These findings prove that respiratory-type epithelium separated from an aerated middle ear does not undergo changes into keratin-forming epithelium.