The hybrid epidermoid and apocrine cyst. A combination of apocrine hidrocystoma and epidermal inclusion cyst.

We describe four cases of unusual superficial cutaneous cysts that have a lining epithelium composed of apocrine cells immediately adjacent to keratinizing squamous epithelium with an intact granular layer. Two of the cysts were on the nipple of the breast and two of the cysts were on the face. The lumina of all four cysts contained keratin. Immunoperoxidase staining for carcinoembryonic antigen in the facial cysts showed positive staining within the apocrine cells of the lining epithelium in one case. The pathogenesis of these lesions is uncertain. We suggest that these unusual cysts be called hybrid epidermoid and apocrine cysts.