Mohs surgery for early-stage Merkel cell carcinoma (MCC) achieves local control better than wide local excision ± radiation therapy with no increase in MCC-specific death.

BACKGROUND Merkel cell carcinoma (MCC) of the skin is most commonly treated with wide local excision (WLE) with or without adjuvant radiation therapy (RT). Mohs micrographic surgery (MMS) as monotherapy may offer an alternative treatment modality. The purpose of this study is to describe outcomes of patients with primary Stage I/II MCC treated with MMS alone and no RT. METHODS A retrospectively collected sample of 56 MCCs treated with MMS was studied over an 18-year period. Tumor and treatment characteristics were described, and follow-up was assessed. RESULTS A total of 56 primary Stage I/II MCCs in 53 patients were treated with MMS as monotherapy from April 2001 through July 2019. Patients were followed for an average of 4.6 years (median 2.7 years, range 0.8 to 16.9 years), of which 19 (33.9%) had follow-up of 5 years or more. There were no local recurrences due to inadequate excision. The 5-year Kaplan-Meier MCC-specific survival for AJCC8 Stage I and AJCC8 Stage IIA were 91.2% and 68.6%, respectively. CONCLUSION In comparison to historical controls, Mohs surgery offers a survival that is at least as good as WLE +/- RT, with the added benefits of no need for adjuvant RT or the need for further surgery for treatment of local recurrence.