Parotid metastasis of Merkel cell carcinoma in a young patient with ectodermal dysplasia. Diagnosis by fine needle aspiration cytology and immunocytochemistry.

Fine needle aspiration (FNA) biopsy was performed on an intraparotid lymph node metastasis of a Merkel cell carcinoma of the eyelid in a 15-year-old girl with antecedent ectodermal dysplasia syndrome. The cytologic appearance of the aspirate and the results of immunocytochemical typing of intermediate filaments on the FNA smears provided a definitive diagnosis. The Romanowsky stain provided an excellent delineation of paranuclear intracytoplasmic "buttons," which appeared to contain both cytokeratin and neurofilaments by immunocytochemical studies. These findings confirm previous data emphasizing the role of light microscopic observations, supplemented by proper immunocytochemical investigations, in the differential diagnosis of metastatic Merkel cell carcinoma in fine needle aspirates.