Lymphoepithelioma-like carcinoma of the skin

Carcinomas histologically resembling nasopharyngeal lymphoepithelioma have been identified in the salivary gland, thymus, tonsil, and uterine cervix. Five patients with similar tumors primary in the skin are described. The patients ranged in age from 50 to 81 yr. Four neoplasms were situated on the head, and one was located on the shoulder. Microscopically, they were concentrated in the mid- and deep dermis and lacked connections with epidermis. The pattern was of multiple nodules, smaller irregular islands, and cords. The uniform tumor cells had moderate amounts of lightly eosinophilic cytoplasm and vesicular nuclei with one or two prominent nucleoli. A lymphoid infiltrate was intimately associated with each neoplasm and obscured the malignant epithelium in one. Neither squamous nor glandular differentiation was present, but all tumors exhibited intracytoplasmic mucin. Immunohistochemistry was positive for cytokeratin (5 of 5; diffuse) and epithelial membrane antigen (4 of 5; 3 diffuse, 1 focal). Focal reactivity was also noted for carcinoembryonic antigen (1 of 5), neuron-specific enolase (1 of 5), and vimentin (1 of 5). S100 protein, leukocyte common antigen, Factor VIII-related antigen, prostate-specific antigen (males), Leu M1, and salivary amylase reactivity were absent. One patient developed local recurrence and metastases after 39 mo and was dead of disease at 57 mo. The remaining four were free of disease after 46, 27, 25, and 6 mo of follow-up. The diagnosis of lymphoepithelioma-like carcinoma of the skin is based on microscopic findings and exclusion of occult malignancy. The tumor can be confused with a lymphoid infiltrate and is differentiated from Merkel cell carcinoma primarily on cytologic grounds. The neoplasm may be of adnexal origin.