A Merkel-cell carcinoma metastatic to the tonsil: a case report and review of the literature.

Metastatic tumors to the palatine tonsils are extremely rare, with nearly 100 cases reported. Only 3 cases of Merkel cell carcinoma of the skin metastasizing to the palatine tonsil have been reported. We present the interesting case of a 61-year-old man with an enlargement of the left palatine tonsil that caused a moderate narrowing of the oropharynx. Three years previously he had been treated for Merkel cell carcinoma (MCC) on skin of his left shoulder. A tonsillectomy followed by palatoplasty was performed. Immunohistochemical staining demonstrated a pronounced reaction for cytokeratin 20, chromogranin, and CD56 histodiagnostic markers. Immunohistochemical studies are useful diagnostic tools in the establishment of the diagnosis of MCC. Treatment includes wide local surgical excision of the tumor, radiotherapy, and chemotherapy. Considering the aggressiveness of MCC, an early diagnosis is critical to enable the choice of adequate therapy at an early stage.