Primary merkel cell carcinoma of the oral mucosa: a case report with review of literature

We present a case of primary Merkel cell carcinoma in the oral mucosa of a 60-year-old man. The patient underwent incisional biopsy of the tumor. Histologically, the tumor was composed of small monotonous cells in a solid sheet-like and single-cell row growth pattern. Immunohistochemically, tumor cells were positive for pancytokeratin, CD56, and synaptophysin, and negative for leukocyte common antigen, vimentin, S-100 protein, HMB45, and thyroid transcription factor 1. Cytokeratin 20 staining showed a paranuclear dot-like pattern in tumor cells. Therefore, the diagnosis of Merkel cell carcinoma was made. The patient received chemotherapy with etoposide and cisplatin followed by 62 Gy radiation in 31 fractions over seven weeks. Follow-up brain CT scans after three and five months showed complete remission of the mass and enlarged lymph node. He is currently doing well with no evidence of recurrence. The present case is the first report of Merkel cell carcinoma arising in the buccal vestibule. The patient is currently doing well with no evidence of recurrence at six months.