Mohs Surgery for Melanoma
For non-melanoma skin cancers, such as basal cell carcinomas and squamous cell carcinomas, an alternative ‘tissue-sparing’ procedure is frequently performed called Mohs Micrographic Surgery. In some cases – and at some clinics – Mohs surgery is also being used to treat melanoma in situ (stage 0) or lentigo maligna melanoma, a subtype of melanoma that typically occurs on sun-damaged skin.
What Happens During Mohs Surgery:
During Mohs surgery, cancer is removed one layer at a time in an outpatient setting (no overnight stay required). Mohs Surgery is usually performed under local anesthesia. After each layer is removed, it is then carefully examined under a microscope. A technician determines whether or not all cancer cells have been removed from the tissue sample. This cycle of single-layer tissue removal and microscopic evaluation continues until cancer cells are no longer found.
What Happens During 'Slow Mohs' Surgery:
In this variation of Mohs surgery often used for lentigo maligna melanoma, your surgeon will remove any visible skin cancer and a little bit of normal looking skin around it. The patient is then bandaged and sent home overnight. The tissue sample is sent to pathology lab where a dermatopathologist reviews the tissue. Overnight processing allows better visualization of the tissue and helps the dermatopathologist more definitively assess if cancer cells are present and if the margins are clear. The next day, you’ll return to the clinic where the surgeon will either close the wound or remove additional layers of tissue based on the dermatopathologist’s findings. This process is then repeated until no additional melanoma is detected.
What are the Benefits of Mohs Surgery?
While more time consuming, Mohs surgery is a more precise technique than the traditional wide local excision and allows a surgeon to confirm that all cancerous cells are removed before stitching the wound. This preserves more tissue and leaves smaller scars.
What are the Potential Risks of Mohs Surgery?
While regularly used for non-melanoma skin cancers, Mohs surgery is used less frequently for melanoma in situ because melanoma is far more aggressive (and likely to spread) than other types of skin cancer.
In addition, while the edges of non-melanoma skin cancers are easy to see under a microscope, melanoma cells – especially atypical melanoma cells – are harder to detect. However, in recent years, researchers have refined the Mohs technique with the addition of special colored stains – called immunohistochemistry stains – that preferentially stick to the cells that develop melanoma, causing them to be a different color than the surrounding cells. This makes melanoma cells easier to detect under a microscope.
What Does Research Say About Mohs Surgery for Melanoma?
A retrospective study of 662 patients with melanoma in situ, treated with either Mohs or Wide Local Excision, found no significant difference in the rate of recurrence, melanoma-specific survival, or overall survival between the two groups.1
Despite being a small retrospective analysis, which by design does lend itself to increased risks of bias and confounding effects compared to prospective studies, the study’s results are encouraging. If the findings are verified in a larger, randomized trial, patients who need complex surgery to remove melanoma in situ from sensitive areas—the head, face, hands, and neck—could have more treatment options.
Given the limited data available, Mohs surgery is still not routinely performed for invasive melanoma of the skin; however, it has been recognized over the past decade as an option for melanoma in situ. This is especially the case for the lentigo maligna type associated with chronic sun damage, in both the American Academy of Dermatology and National Comprehensive Cancer Network melanoma clinical practice guidelines.