Cytologic and immunohistochemical diagnosis of neuroendocrine (Merkel cell) carcinoma in cerebrospinal fluid.

Neuroendocrine (Merkel cell) carcinoma of the skin is a rare entity. Often locally aggressive, this lesion may also metastasize to organ systems, including bone, liver, and brain. The authors report a case of a 64-year-old male who presented with hoarseness and dysphagia 17 months after resection of a primary Merkel cell carcinoma of the nose. Additional studies revealed bilateral vocal cord paralysis secondary to central nervous system dysfunction. Cytologic evaluation of the cerebrospinal fluid revealed malignant tumor cells consistent with metastatic Merkel cell carcinoma. Presented are the cytologic and immunohistochemical findings in a case of metastatic Merkel cell carcinoma involving the central nervous system.