What Is Mohs Micrographic Surgery (MMS) for Skin Cancer?
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What Is Mohs Micrographic Surgery (MMS) for Skin Cancer? How Long Does MMS Take?
Mohs Micrographic Surgery (MMS) is a specialized surgical technique used to treat skin cancer that combines surgical excision with immediate pathological examination. This method was developed by Dr. Frederic E. Mohs and is currently regarded as one of the most effective treatments for skin cancer, significantly reducing the likelihood of recurrence. It is particularly effective for non-melanoma skin cancers, such as basal cell carcinoma and squamous cell carcinoma.
The technique allows for a comprehensive analysis of the cancer’s margins, ensuring a 100% microscopic tissue margin examination while minimizing the loss of surrounding healthy tissue. This surgery can typically be completed in one day, with no need for hospitalization.
Steps of Mohs Micrographic Surgery (MMS)
- The procedure begins with the administration of local anesthesia.
- First Layer Excision: The surgeon removes a thin layer of skin from the area containing the cancer. The wound is then covered with gauze, and the tissue sample is sent for pathological examination under a microscope to identify any remaining cancer cells.
- Waiting for Results: The patient will wait approximately 2 hours for the results of the tissue examination.
- Repeat Excision: If cancer cells are still detected, the surgeon will repeat the excision using the same method, targeting only the areas where cancer remains, until no cancer cells are found.
- Wound Closure: Once no cancer cells are detected, the surgeon will either close the wound with stitches or allow it to heal naturally, depending on the size and location of the wound, as appropriate.
Differences Between Wide Excision and Mohs Micrographic Surgery (MMS) for Skin Cancer
Wide excision is the traditional surgical method for treating skin cancer, and it differs from Mohs Micrographic Surgery (MMS) in the following ways:
1. Surgical Method
- Wide Excision: This approach involves removing the cancerous tissue along with a margin of surrounding healthy tissue. The surgical margin is determined based on the type of cancer, and the entire specimen is sent for pathological examination.
- MMS: This technique removes the cancerous skin layer by layer. Each layer is examined pathologically, and if cancer cells are detected, the next layer is excised until no cancer cells remain.
2. Pathological Analysis
- Wide Excision: The tissue is analyzed vertically using a technique similar to bread loafing. This method may miss residual cancer cells in areas that are not sliced, especially in cancers with unclear borders.
- MMS: The tissue is analyzed horizontally, allowing for a comprehensive assessment of the cancer’s spread, achieving 100% evaluation of the microscopic margins.
3. Recurrence Rates
- Wide Excision: There is a higher risk of cancer recurrence if any cancer cells are left within the excised margins.
- MMS: The recurrence rates are lower. For primary basal cell carcinoma, the 5-year cure rate after treatment is approximately 99% with MMS, compared to 90% for standard excision. For primary squamous cell carcinoma, the rate is 97% for MMS versus 92% for standard excision.
4. Size of Surgical Wound
- Wide Excision: This method typically may result in larger surgical wounds as more surrounding tissue is removed.
- MMS: The surgical wounds are generally smaller due to the preservation of normal tissue around the cancer.
5. Treatment Time and costs
- Wide Excision: This method usually requires less time
- MMS: It may take longer due to the need for immediate pathological analysis during the procedure, resulting in higher costs.
Skin Cancers That Should Be Treated with MMS
- Recurrent Skin Cancer
- Tumors located in areas prone to recurrence, such as the central face, around the eyes, nose, lip, chin, ears, anogenital region, hands, feet, nail units, ankles, and nipples.
- Skin cancers larger than 2 centimeters.
- Skin cancers that grow rapidly and are more aggressive in nature.
- Skin cancers with unclear margins
- Skin cancers that develop on scar tissue.
- Skin cancers that could not be completely removed during standard surgical procedures.
- Skin cancers that arise in areas previously treated with radiation.
- Skin cancers in individuals with compromised immune systems.
References:
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- Krakowski AC, Hafeez F, Westheim A, Pan EY, Wilson M. Advanced basal cell carcinoma: What dermatologists need to know about diagnosis. J Am Acad Dermatol. 2022 Jun;86(6S):S1-S13.
- Fania L, Didona D, Morese R, Campana I, Coco V, Di Pietro FR, Ricci F, Pallotta S, Candi E, Abeni D, Dellambra E. Basal Cell Carcinoma: From Pathophysiology to Novel Therapeutic Approaches. Biomedicines. 2020 Oct 23;8(11):449. doi: 10.3390/biomedicines8110449. PMID: 33113965; PMCID: PMC7690754.
- https://www.aad.org/public/diseases/skin-cancer/find/mole-map
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