Lymphoepithelioma-like carcinoma of the skin with adnexal differentiation.

Lymphoepithelioma-like carcinoma of the skin (LELCS) is a recently-described tumor entity with a microscopic resemblance to undifferentiated carcinoma of the nasopharynx. Only five cases of this lesion have been reported heretofore. We document three additional examples of LELCS that were composed of clustered dermal arrays of cytologically malignant, mitotically active polygonal cells, without connections to the overlying epidermis or skin appendages. Chronic inflammatory cells were interspersed throughout each of the tumors. Two of them demonstrated multiple foci of trichilemmal-type keratinization among the neoplastic cells, whereas the other exhibited focal eccrine ductal or glandular differentiation. None of the neoplasms was found to contain nucleic acid of Epstein-Barr virus by in situ hybridization. It is postulated that LELCS represents a primitive cutaneous appendage tumor. Based on the results of a prior publication and those of the current assessment, this neoplasm is thought to have the potential for both sweat glandular and follicular differentiation.