What does MOHS (Microscopic Observation of Hemorrhage and Surgical) stand for in the context of skin cancer treatment?

What Does MOHS Stand For in Skin Cancer Treatment?

MOHS stands for Micrographic Surgery, a specialized surgical technique that offers the highest cure rates for skin cancer while preserving the maximum amount of healthy tissue. 1

Origin and Definition

MOHS is named after Dr. Frederic Mohs who first described the use of chemosurgery for removal of difficult or recurrent cutaneous tumors in the 1940s 1. The technique was later adapted to the "fresh tissue" technique by Tromovitch and Stegman, which eliminated the pain from in vivo fixation with zinc chloride paste, shortened surgery time, and allowed immediate repair of fresh surgical wounds 1.

Key Features of MOHS Surgery

• Complete margin assessment: MOHS involves excision with complete circumferential peripheral and deep margin assessment (CCPDMA) 1
• En face sectioning: Horizontal frozen sections allow examination of 100% of surgical margins, unlike traditional "bread loaf" sectioning 1, 2
• Immediate pathology: The surgeon acts as both surgeon and pathologist, examining tissue immediately during the procedure 2
• Tissue mapping: Residual tumor is graphically mapped to guide precise removal of remaining cancer cells 2, 3
• Tissue preservation: Maximum sparing of tumor-free adjacent tissue optimizes wound reconstruction 3

Indications for MOHS Surgery

MOHS is primarily indicated for:

• High-risk basal cell carcinomas (BCCs) 1
• Recurrent skin cancers 1
• Tumors in cosmetically and functionally sensitive areas, particularly the face 4
• Tumors with poorly defined clinical margins 1
• Aggressive histologic subtypes (sclerosing/morpheaform) 1
• Squamous cell carcinomas in high-risk locations 1
• Dermatofibrosarcoma protuberans (DFSP) 1

Effectiveness of MOHS Surgery

MOHS offers superior cure rates compared to other treatment modalities:

• 99% cure rate for primary BCCs 5
• 94.4% cure rate for recurrent BCCs 5
• 5-year recurrence rates of only 1% for primary and 5.6% for recurrent BCCs 1

Alternatives to MOHS

When MOHS is unavailable, alternatives include:

• Standard excision with wider surgical margins 1
• Radiation therapy for non-surgical candidates 1
• Topical therapies for superficial BCCs (imiquimod, 5-fluorouracil) 1
• Cryosurgery for selected low-risk BCCs 1

Common Pitfalls and Caveats

1. Appropriate patient selection: MOHS is not necessary for all skin cancers - it should be prioritized for high-risk tumors 5
2. Complete margin assessment: If complete margin assessment isn't possible due to anatomic structures (major vessels, nerves, bone), multidisciplinary discussion may be needed 1
3. Avoid wide undermining: This is discouraged prior to confirmation of clear margins as it can make interpretation of re-excised margins difficult 1
4. Reconstruction timing: For complex cases, consider delaying wound closure until pathology confirms clear margins 5
5. Follow-up importance: Even with MOHS, clinical follow-up is recommended every 3-6 months for the first 2 years 5

MOHS micrographic surgery represents the gold standard for treating high-risk skin cancers, particularly on the face, offering both the highest cure rates and maximum tissue preservation when performed by appropriately trained surgeons.