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Mohs micrographic surgery may be used for melanoma in situ beyond excision margins

Mohs micrographic surgery was used effectively to treat melanoma in situ exceeding traditional excision margins of 5 mm, according to published study results.

Researchers examined the long-term outcomes of 882 primary or recurrent melanoma in situ tumors (mean patient age, 62 years; 52.4% male) located on the trunk or proximal extremity and treated with Mohs micrographic surgery (MMS), and compared the outcomes with those of historical controls. Surgical margin intervals determined complete excision rates.

There were 429 melanoma in situ cases that had previously been reported in a separate study, and 453 additional patients treated between 2008 and 2014, with 7 years’ additional follow-up for the initial set of cases.

Dermatopathology reports determined 23% of melanoma in situ tumors were classified as lentigo maligna or non-lentigo maligna subtype.

Most of the melanoma in situ tumors (83%) cleared with a margins of 6 mm, while margins of 9 mm were necessary for 97% clearance. Margins of 12 mm or more were required for the remaining 3% of patients to achieve complete excision.

One local recurrence occurred in the study. No primary melanoma in situ treated with MMS recurred, and one recurrent melanoma in situ recurred (overall recurrence rate, 0.1%). The patient was a 64-year-old woman who had initially presented with a 2.8 cm melanoma in situ of the trunk in 1986.

“Guidelines for the treatment of melanoma published by the [American Academy of Dermatology] acknowledge the importance of complete tumor removal,” the researchers wrote.

“In the previous study we were able to identify and treat 148 patients with tumors extending beyond traditional surgical margins. Primary treatment of these melanoma outliers before recurrence along with the low recurrence rates (0.1%) achieved strongly supports the efficacy of MMS as a treatment option for patients with trunk and proximal extremity [melanoma in situ]. When treating patients with wide local excision, margins closer to 1 cm may achieve better rates of excision.

“This study may prove useful when considering the surgical treatment of patients with melanoma, and may be beneficial for future updates on Mohs appropriate use criteria.” – by Bruce Thiel

Disclosure: The researchers report no relevant financial disclosures.