If you've been diagnosed with basal cell carcinoma (BCC) or squamous cell carcinoma (SCC), your dermatologist may have recommended Mohs micrographic surgery. It's a name that can sound intimidating — but understanding exactly what it is, and why it's considered the gold standard for certain skin cancers, often puts patients at ease. This guide covers everything you need to know.
What Is Mohs Surgery?
Mohs micrographic surgery is a precise, tissue-sparing surgical technique for removing skin cancer. It was developed in the 1930s by Dr. Frederic Mohs and refined over subsequent decades into the procedure used today. The defining feature of Mohs is that the surgeon acts simultaneously as the surgeon and the pathologist: tissue is removed in thin layers, immediately processed and examined under a microscope by the same physician, and the procedure continues only until the surgical margins are completely clear of cancer cells.
This real-time, complete margin assessment is what sets Mohs apart. Standard excision typically examines only about 1% of the surgical margin through "bread-loaf" sectioning — meaning cancer cells at the edges can be missed. Mohs examines 100% of the margin, layer by layer, which is why cure rates are so high.
Who Is a Candidate for Mohs Surgery?
Mohs is not appropriate for every skin cancer. It is most beneficial when tissue conservation is critical or when cancer characteristics increase recurrence risk. Ideal candidates include:
- Skin cancers on the face, ears, nose, lips, eyelids, scalp, hands, or genitalia — areas where sparing healthy tissue matters most for function and appearance
- Recurrent tumors that have been previously treated and come back
- Tumors with aggressive histologic subtypes (e.g., morpheaform or infiltrative BCC, poorly differentiated SCC)
- Tumors with poorly defined borders that are difficult to assess clinically
- Large tumors or those with perineural or perivascular invasion
- Patients who are immunocompromised and at higher risk for aggressive disease
Not all skin cancers require Mohs. Small, low-risk BCCs or SCCs on the trunk or extremities are often treated effectively with standard excision or other methods. During your consultation, Dr. Qiblawi will assess the specific features of your tumor and recommend the most appropriate treatment — which may or may not be Mohs.
Step-by-Step: What to Expect on the Day of Surgery
Mohs surgery is performed as an outpatient procedure under local anesthesia. Patients remain awake and comfortable throughout. Plan for the appointment to take several hours, as waiting between stages is part of the process.
Marking and Local Anesthesia
The tumor site is cleaned and marked. Local anesthetic (lidocaine) is injected to completely numb the area. Most patients feel only the initial needle stick; the procedure itself is painless.
First Layer Removed
A thin, saucer-shaped layer of tissue is excised along with a small margin of surrounding normal-appearing skin. The wound is temporarily bandaged. A map (diagram) of the tissue is created, and the specimen is carefully oriented and color-coded.
Laboratory Processing (Waiting Period)
The tissue is processed, sectioned, and stained in the on-site laboratory. This typically takes 45–90 minutes. Patients wait comfortably in the office — bring a book or something to do.
Microscopic Examination
Dr. Qiblawi examines all tissue margins under a microscope. If cancer cells are seen at any margin, their precise location is marked on the tissue map.
Additional Layers as Needed
If cancer remains, only the exact area where cancer cells were found is removed — sparing all cancer-free tissue. Steps 2–4 repeat until margins are completely clear. Most tumors clear in 1–3 stages. About 80% of cases require only one or two stages.
Wound Repair
Once clear margins are confirmed, the wound is repaired. Options include primary closure (sutures), skin flap, skin graft, or allowing the wound to heal naturally (second-intention healing). The repair method depends on wound size, location, and what will achieve the best functional and cosmetic outcome.
Before Your Procedure: How to Prepare
- Continue most medications as prescribed — do not stop blood thinners (aspirin, warfarin, clopidogrel) without explicit instruction from your prescribing physician, as stopping these can carry cardiac or stroke risk that outweighs bleeding risk during Mohs
- Eat a normal breakfast the morning of surgery; you will not be under general anesthesia
- Wear comfortable, loose clothing appropriate for the site being treated (e.g., button-down shirt for facial surgery)
- Arrange a driver if the surgery site may affect your driving — particularly for procedures near the eyes
- Plan for a full day; bring entertainment, snacks, and any medications you take during the day
- Avoid alcohol for 24 hours prior, as it can increase bleeding
Recovery and Aftercare
Recovery depends primarily on wound size and repair method. General guidelines:
- Keep the wound covered and moist with petrolatum (Vaseline) — do not let it dry out. Moist wound healing significantly reduces scarring
- Avoid strenuous activity for 1–2 weeks to minimize bleeding risk and allow proper healing
- Sutures are typically removed at 5–14 days depending on location (face: 5–7 days; scalp/trunk/extremities: 10–14 days)
- Expect swelling and bruising in the first few days, particularly around the eyes
- Scars typically take 12–18 months to fully mature and fade; scar-minimizing treatments (silicone gel, sun protection) can help
- Follow up with routine skin exams — patients who have had one skin cancer are at significantly elevated risk for additional tumors
Mohs vs. Other Skin Cancer Treatments
- Standard surgical excision: Appropriate for many low-risk tumors; slightly lower cure rates due to incomplete margin assessment. Simpler procedure; one visit
- Electrodesiccation and curettage (ED&C): Scraping and burning; effective for superficial, low-risk BCCs; no margin assessment; good for elderly or patients who can't tolerate surgery well
- Radiation therapy: An option for patients who cannot undergo surgery; useful for very large tumors or those near critical structures; requires multiple visits; no tissue for pathologic confirmation
- Topical immunotherapy (imiquimod, 5-FU): For superficial BCC only; lower cure rates; appropriate for select patients with contraindications to surgery
Have You Been Diagnosed with Skin Cancer?
Dr. Qiblawi is residency-trained in Mohs micrographic surgery and complex reconstruction. If you've been diagnosed with BCC or SCC and want to discuss your treatment options, contact Summit Dermatology for a consultation.
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