Hybrid cysts of the eyelid with follicular and apocrine differentiation: An under-recognized entity?

PURPOSE: To describe 6 patients with hybrid cysts of the eyelid that demonstrated follicular and apocrine differentiation. METHODS: Clinicopathologic series of 6 cases obtained from review of 1,099 cases of hidrocystoma diagnosed at the New York Eye and Ear Infirmary from 1990 to 2006. RESULTS: Six patients, aged 38 years to 85 years (mean 66.5 years), was examined for cystic eyelid lesions. Histopathologic evaluation revealed cystic structures, lined by a combination of apocrine, infundibular (epidermoid), and trichilemmal-type epithelia. Luminal contents consisted of variable amounts of lamellated and compact keratin, and serous material. Contiguity with a hair follicle was demonstrated in 4 of 6 lesions. Immunohistochemical evaluation showed intense immunoreactivity of the entire cyst lining in all lesions for high molecular weight cytokeratin and variable immunoreactivity for low molecular weight cytokeratin. All cystic structures displayed immunoreactivity for carcinoembryonic antigen. Weak focal immunoreactivity for S-100 protein and gross cystic disease fluid protein-15 was observed in most lesions. CONCLUSIONS: Hybrid cysts can show apocrine, trichilemmal, and infundibular differentiation, suggestive of their origin at the junction of keratinizing squamous and glandular epithelia of the hair follicle. Although, to our knowledge, only 1 such lesion has been described in the eyelid skin, it is likely that hybrid cysts of the eyelid are not an infrequent finding.