Dermatology Book

Hematology and Oncology

  • Mohs Micrographic Surgery


Mohs Micrographic Surgery

Aka: Mohs Micrographic Surgery
  1. History
    1. Originally described by Frederick Mohs in 1941
  2. Indications
    1. Non-Melanoma skin cancer
      1. Basal Cell Carcinoma
      2. Squamous Cell Carcinoma
    2. High risk tumors
      1. Sites where tissue preservation is critical
        1. Head and neck tumors (Eyelids, nose, ears, lips)
        2. Tumors on fingers
        3. Tumors on genitalia
      2. Large tumors (Varies by site: 6 mm on face)
      3. Aggressive tumor on histology (see specific tumors)
      4. Immunosuppressed patients
      5. Tumors with poorly defined margins
  3. Contraindications
    1. Melanoma
  4. Technique: Performed by a Dermatologist or Surgeon
    1. Step 1: Prepare site
      1. Anesthesia: Local Anesthetic
      2. Curette soft tumor residual from initial biopsy
    2. Step 2: Excise tumor
      1. Excise visible tumor with 2 mm margins of normal skin
      2. Mark orientation with dye (12:00 is cephalad)
    3. Step 3: In-office histology (requires ~45 minutes)
      1. Frozen sections examined by Mohs surgeon
      2. Surgeon maps out positive margins
    4. Step 4: Excise residual tumor
      1. Return to step 2 using positive margin map as guide
      2. Requires 2 stage excision on average
    5. Step 5: Incision closure
      1. Small lesions: Healing by secondary intent
      2. Larger lesions: Reconstruction
        1. Closure may be delayed for weeks in some cases
  5. Advantages
    1. Highly effective in Basal Cell Carcinoma
    2. Rapid histology results best guides excision
    3. Optimal cosmetic results in sensitive areas
    4. Similar cost to simple excision with histology
  6. Adverse Effects
    1. Scarring
    2. Hematoma (drain placed at surgery in some cases)
      1. Anticoagulants need not be stopped before surgery
    3. Reconstructive tissue graft or flap necrosis
      1. Higher risk in Tobacco Abuse
      2. May occur secondary to Hematoma
    4. Wound Infection (Occurs in 3% of cases)
  7. References
    1. Bowen (2005) Am Fam Physician 72(5):845-8 [PubMed]
    2. Shriner (1998) J Am Acad Dermatol 39:79-97 [PubMed]

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