Palpebro-orbital apocrine cystadenoma: immunohistochemical verification of a unique variant with a critical differential diagnosis.

PURPOSE: To describe a unique apocrine cystadenoma of the superonasal eyelid and anterior orbit.
METHODS: Clinical evaluation with axial and coronal CT; histopathologic and immunohistochemical studies including sections stained with hematoxylin-eosin, periodic acid Schiff, alcian blue, mucicarmine, and Prussian blue for iron; and monoclonal antibodies against cytokeratin-7, epithelial membrane antigen, smooth muscle actin for myoepithelial cells, gross cystic disease fluid protein-15 for apocrine differentiation, and CD-68 and lysozyme for histiocytes.
RESULTS: The cyst possessed a multilaminar lining composed of polygonal to low cuboidal cells. A stalk of solid tumor ingrowth from the wall was composed of adenomatous units of eosinophilic cells with apical snouts ("decapitation secretion"). No goblet cells were discovered. Both the cyst's lining cells and the adenoma expressed gross cystic disease fluid protein-15 indicative of apocrine differentiation. The adenoma displayed inner adlumenal cells that were CK-7 and epithelial membrane antigen positive, and outer myoepithelial cells that were smooth muscle actin positive. Simple local excision was curative.
CONCLUSION: This unique lesion is the first example in the ophthalmic and dermatopathologic literatures of a solid adenoma encompassed by an apocrine cyst, which more typically features short or blunt papillae. It must be distinguished from other eyelid and/or anterior orbital cystic lesions including eccrine hydrocystomas; classical and extratarsal dermoid cysts; congenital and acquired conjunctival cysts and dermoids; dacryocystocoeles/mucoceles; canaliculops and lacrimal gland dacryops; and congenital cystic odontogenic choristomas.