Background. Merkel cell carcinoma (MCC) is an uncommon skin tumor that most frequently arises on sun-exposed facial sites. It rarely occurs on mucous membranes of the head region. The primary MCC is usually treated by wide excision followed by radiation to the primary site and regional lymph nodes. Using traditional surgery the local recurrence rate ranges from 20 to 50%. In our clinic, Mohs surgery is used to excise the primary MCC completely, followed by radiation. Here we present our treatment experiences and outcomes.
Objective. To document our experience of MCC treated by Mohs surgery. We present our series of 12 cases of MCC, 2 cases of which arose from mucosal sites of the nasal cavity.
Methods. We reviewed 12 cases of MCC from the Mohs clinic database. We also reviewed the literature for cutaneous and mucosal MCC.
Results. There were 12 cases of MCC: 10 cutaneous and 2 mucous. The site distribution of cutaneous MCC was eight on the head, one on the neck, and one on the groin. Of these, nine were treated by Mohs excision. Two patients developed local recurrence following Mohs treatment. The local recurrence rate was 22% (2 of 9). The sites of mucosal MCC were the nasal septum and nasopharynx. One case had a history of previous radiation and developed an MCC 40 years later. This case also demonstrated epidermotropic spread of Merkel cells to the overlying mucous epithelium. This patient required extensive intranasal and cranial surgery to remove the tumor. Both patients with mucosal MCCs died of their disease. The overall mucocutaneous survival of MCC at 1 year was 80% and at 2 years was 50%.
Conclusion. In our series, local control of the primary MCC was achieved in 70% of patients (7 of 10) using combined Mohs excision and radiation. Two recurrences had primary tumors larger than 3.5 cm in diameter, while the other case was nonresectable by Mohs surgery. Tumor size appeared to determine the degree of local control. When the postoperative Mohs defect was less than 3.0 cm in diameter, local and regional control appeared to be more favorable. When the primary facial MCC is relatively small, removal by Mohs surgery followed by radiation was effective, therapeutic, and less disfiguring. Mucosal MCC is rare and may occur as a long-term sequelae after radiation therapy to the skin.