Papillary eccrine adenoma in association with cutaneous horn.

Papillary eccrine adenoma (PEA) is an uncommon sweat gland neoplasm that occurs more frequently on the distal extremities of Black women. Clinically, it appears as a small, isolated, firm, dome-shaped cutaneous nodule. We report two unusual cases of PEA that presented clinically as cutaneous horn. Histologically, both cases showed the typical dermal morphology of PEA with overlying epidermal changes suggestive of human papillomavirus (HPV). However, HPV immunoperoxidase staining and polymerase chain reaction for HPV were negative in both cases. Concurrent occurrence of PEA and HPV-like epidermal changes may be coincidental; however, their co-occurrence may also be related to the environment induced by this adnexal tumor. Whether PEA with verrucous epidermal changes has a different clinical behavior or increased risk for a malignant transformation is unknown, as both patients were lost to follow-up.