[Lymph node metastasis of Merkel cell carcinoma without known cutaneous primary - case report].

Merkel cell carcinoma is a rare cutaneous tumor with an aggressive clinical course. In most cases it is associated with Merkel cell polyomavirus infection. Exceptionally, the tumor can present as a lymph node metastasis without a discernible cutaneous primary. In this report we present the case of a 42 year-old man with inguinal lymphadenopathy, histologically consistent with Merkel cell carcinoma. Tumor cells expressed immunohistochemically chromogranin-A, synaptophysin and displayed dot-like positivity for cytokeratin 20. The genome of MCPyV in neoplastic cells was detected using real-time PCR. A cutaneous primary has not been identified neither during the dermatologic examination, nor with PET CT scan.