Mohs micrographic surgery (MMS) is considered the gold standard of treatment for many skin cancers. However, this option is not always appropriate for every situation and every patient. Several factors should be considered when determining which option to use, including tumor size, patient age, and aesthetic outcomes, for treating skin cancer.
At the ODAC Dermatology, Aesthetic and Surgical Conference in Orlando, FL, Sailesh Konda, MD, and Vishal Patel, MD, reviewed the guidelines and discussed considerations for when and when not to perform MMS.1
Sailesh Konda, MD, assistant clinical professor of dermatology at the University of Florida (left).
Dr Konda is assistant clinical professor of dermatology and director of Mohs surgery and surgical dermatology at the University of Florida College of Medicine. Dr Patel is assistant professor of dermatology and director of the Cutaneous Oncology Program at George Washington University School of Medicine.
Vishal Patel, MD, assistant professor of dermatology at George Washington University (right).
The Dermatologist: What are the guidelines for determining what tumors should and should not be treated with MMS?
Dr Konda: The appropriate use criteria (AUC) for MMS was developed in 2012 by an ad hoc task force.2 In general, MMS may be considered as a treatment option for tumors on the head, neck, hands, feet, pretibial surface, ankles, and genitalia; aggressive tumors of any location; tumors greater than 2 cm on trunk or extremities; recurrent tumors, and tumors arising in patients with a history of immunosuppression, radiation, or genetic syndromes.
An AUC score is assigned to tumors based on their characteristics. Tumors with scores of 7 to 9 are appropriate, 4 to 6 are uncertain (in extenuating circumstances, MMS may be considered), and 1 to 3 are inappropriate.
However, practitioners should remember that these are only guidelines! Even if a tumor meets criteria for MMS, the physician and patient should still discuss all available treatment options—both surgical and nonsurgical— and take into consideration associated cure rates; long-term clinical and aesthetic outcome; the patient’s age and comorbidities; and risks, benefits, and adverse effects before deciding on a treatment.
The Dermatologist: What tumors often deemed appropriate for MMS might not actually require MMS, and why?
Dr Konda: Superficial basal cell carcinoma and squamous cell carcinoma in situ are tumors that have been deemed appropriate for MMS. However, these tumors may also be treated with topical therapy (imiquimod and 5-fluorouracil), local destruction, fusiform or disc excision, photodynamic therapy, and lasers (CO2 +/- diode for follicular extension). These treatment modalities may provide cure rates lower than but approaching those of MMS, and may be preferred by physicians and patients in certain circumstances. When discussing treatment options, patients should be made aware of any therapies that may be used off-label or are not FDA-approved.
Additionally, lentigo maligna (melanoma in situ) and lentigo maligna melanoma may be treated with either MMS (frozen sections), staged excision with central debulk and complete margin assessment (permanent sections), or wide local excision (permanent sections).
There is some debate with regards to the accuracy of frozen sections vs permanent sections. Permanent sections are considered to be the gold standard for melanocytic lesions. When evaluating frozen sections, it may be difficult to distinguish non-malignant melanocytic hyperplasia occurring in chronically sun-damaged skin from melanoma in situ. Furthermore, there is currently no consensus on how to deal with single atypical melanocytes at the outermost edges of a lesion.
A proposed solution is to take control biopsies from adjacent or contralateral skin to serve as a measure of background melanocytic density. Until best practices are developed for MMS for melanoma, staged excisions, which combine complete margin assessment with permanent section evaluation, may offer the best of both worlds.
The Dermatologist: What tumors that have traditionally not been treated with MMS might actually benefit from MMS, and why?
Dr Patel: Evidence continues to show that 100% margin assessment is the best predictor of outcomes. If a practitioner is able to assess the entire margin of a resection, rather than a small portion as done in standard bread-loafed wide local excision, they will have the best chance to prevent a recurrence. MMS is slowly seeing a change in its technical name to margin control surgery or CCPDMA (complete circumferential peripheral and depth margin analysis) surgery, which is a more appropriate name for this technique. The CCPDMA technique allows for the primary benefit of complete margin evaluation and the secondary benefit of tissue sparing, if possible.
MMS or CCPDMA surgery can and should be considered in all types of contentious tumors when the technique can be performed safely. This would include melanoma in situ, invasive melanoma, Merkel cell carcinoma, and dermatofibrosarcoma protuberans, but could also include other types of deeper or more rare tumors that have contiguous growth patterns. To be clear, MMS or CCPDMA does not mean taking smaller margins, but rather taking recommended margins with complete margin evaluation.
The Dermatologist: What takeaways would you like to leave with dermatologists regarding selecting MMS as a treatment for skin cancers?
Dr Patel: Dermatologists are on the front lines of the skin cancer public health crisis and we should be responsible stewards of evidence-based care. Dermatologists should utilize the evidence—specifically, outcomes data regarding recurrence risk, mortality, and disease specific death—to help determine their treatment decisions when considering various surgical and nonsurgical treatment options.
Furthermore, there are many ways to treat low-risk skin cancers with surgery without utilizing MMS or overusing health care resources. One example is disc excision, which has gained traction for the initial biopsy of melanocytic lesions. Disc excision can also be considered in the treatment of keratinocyte carcinomas, as it may lead to less repeat treatments and ultimately lower costs of care for skin cancer.
1. Konda S and Patel VA. Does this skin cancer really need mohs?. Presented at: ODAC Dermatology, Aesthetic and Surgery Conference; January 19, 2020; Orlando, FL.
2. Connolly SM, Baker DR, Coldiron BM, et al. AAD/ACMS/ASDSA/ASMS 2012 appropriate use criteria for Mohs micrographic surgery: a report of the American Academy of Dermatology, American College of Mohs Surgery, American Society for Dermatologic Surgery Association, and the American Society for Mohs Surgery. J Am Acad Dermatol. 2012;67(4):531-550. doi:10.1016/j.jaad.2012.06.009