Eyelid basal cell carcinoma developing in an epidermoid cyst: a previously unreported event.

A 72-year-old woman presented with a 3 × 2 × 1-mm right lower eyelid micronodular, whitish solid lesion at the nasal eyelid margin that had caused madarosis. Local excision led to the microscopic discovery of 2 epidermoid cysts, one of which harbored a basal cell carcinoma arising from its orthokeratinizing squamous cell lining. Poral openings indicated that the cysts represented follicular infundibular ectasias. BER-EP4-positive immunostaining confirmed the basal cell nature of the neoplasm. This is the first example in the eyelid of an epidermoid cyst displaying malignant transformation. No matter how innocent they may appear, all small cystic or noncystic eyelid lesions should be submitted for pathologic evaluation.