Comparison Handout
Mohs Surgery vs. Standard Excision
Overview
When a skin cancer is diagnosed, your doctor will discuss which removal technique is most appropriate. The two most common surgical options are Mohs micrographic surgery and standard (wide local) excision. Both remove the cancer, both are performed under local anesthesia in an outpatient setting, and both have excellent cure rates for appropriate tumors. The key differences lie in how the margins are examined, how much tissue is removed, and how quickly you get results.
Side-by-Side Comparison
| Feature | Mohs Surgery | Standard Excision |
|---|---|---|
| How margins are checked | 100% of the outer margin examined in real time, layer by layer | Approximately 1–2% of the margin examined (random bread-loaf sections); results available in days |
| Cure rate. New (primary) BCC | Up to 99% | Approximately 91–95% |
| Cure rate. New (primary) SCC | Approximately 97% | Approximately 90–95% (margin-dependent) |
| Cure rate. Recurrent tumors | ~94% (BCC), ~90% (SCC) | ~83% (BCC), ~77% (SCC). Significantly lower |
| Time to result | Same day. Cancer confirmed clear before wound is closed | Days to 1 week. Wound closed before margin results are known |
| Amount of tissue removed | Minimal. Only cancerous tissue removed in each pass | Larger fixed margin (typically 4–10 mm) taken around the visible tumor |
| Reconstruction | Delayed until clear margins confirmed; optimal closure planned with full defect known | Closure at time of surgery; if margins are involved, a second procedure may be needed |
| Best for | High-risk locations (face, ears, nose, eyelids), aggressive subtypes, recurrent tumors, immunosuppressed patients, tissue-critical sites | Low-risk tumors on trunk, extremities, and some scalp locations; tumors with well-defined borders |
| Setting | Dermatologic surgery office. All-day procedure (3–5 hours typical) | Dermatology office or operating room. Shorter procedure (30–60 min), but separate lab processing |
| Cost | Generally higher per-procedure cost; covered by most insurance when medically indicated | Generally lower per-procedure cost; widely covered by insurance |
| Scar size | Typically smaller. Only cancer-containing tissue removed | Typically larger. Fixed safety margins taken regardless of actual cancer extent |
When Mohs Surgery Is Recommended
Mohs is generally favored in situations where margin control is critical or where the cancer is at higher risk of recurrence. Common indications include:
- Tumors on the face, especially the 'H-zone' (nose, eyes, ears, lips, temples) where tissue preservation is important for function and appearance
- Tumors with poorly defined or ill-defined borders that are hard to see clinically
- Aggressive histologic subtypes. Morpheaform, infiltrative, micronodular, or basosquamous BCC; poorly differentiated or desmoplastic SCC
- Recurrent tumors that have come back after previous treatment
- Large tumors (>2 cm on the face, >4 cm on the trunk/extremities)
- Tumors with perineural or lymphovascular invasion on the biopsy report
- Patients with weakened immune systems (transplant recipients, HIV, those on immunosuppressive medications)
- Tumors arising in areas of prior radiation therapy or chronic scars
- Situations where preserving the maximum amount of healthy tissue is critical (near the eye, nose tip, lip, ear canal)
When Standard Excision Is Appropriate
Standard excision remains a highly effective, well-established treatment for many skin cancers. It is often the preferred choice in these situations:
- Small, well-defined, low-risk BCCs or SCCs located on the trunk or extremities
- Tumors with low-risk histology: nodular BCC, superficial BCC, well-differentiated SCC
- Locations where tissue conservation is less critical and a wider margin is easily achieved
- Patients who prefer a single-session procedure with immediate wound closure
- Settings where Mohs surgery is not locally available
- Tumors that can be fully excised with confidence based on clinical assessment and adequate surrounding normal tissue
Key Message
Both Mohs micrographic surgery and standard excision are safe and effective treatments endorsed by major dermatology and surgical societies. Neither approach is universally superior. The best choice depends on the individual tumor characteristics, location, and patient factors. Your dermatologist or Mohs surgeon will recommend the technique most appropriate for your specific case. Do not hesitate to ask questions or seek a second opinion if you have concerns.
About This Article
Author: Dr. Yehonatan Kaplan, M.D., Fellow ACMS
Last Medical Review:
Audience: Physicians & Patients
Clinic: Kaplan Clinic · DermUnbound Research Program
This handout presents a balanced overview of two accepted treatment approaches. The best choice depends on your specific tumor type, location, size, and overall health. Discuss all options with your dermatologist or surgeon before making a decision.