Lymph nodal Merkel cell carcinoma: primary or metastatic disease? a clinical case.

We report a case of Merkel cell carcinoma (MCC) presenting in the lymph nodes in the absence of a primary cutaneous site. The MCC was treated by palliative radiotherapy, which controlled the disease locally. Eight months after diagnosis a mass appeared on the ipsilateral knee; histopathological examination of this lesion confirmed the diagnosis of MCC. The patient died two months later due to the development of pulmonary metastases. Interestingly, the neoplastic tissue was confined to the regional lymph nodes for several months before the primary site appeared. Primary lymph nodal MCC is rare and the diagnosis is difficult. In our opinion the only way to make a diagnosis of primary lymph nodal MCC is by appropriate clinical follow-up.