Hyperplasia

Keratoacanthoma

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Keratoacanthoma

  • Epidemiology
  1. Onset later in life
  • Pathophysiology
  1. Squamoproliferative, benign epithelial lesions
  2. No longer thought to be associated with malignancy
    1. Not a squamous cell cancer variant
    2. May be difficult to distinguish from SCC (see below)
  • Risk Factors
  1. Ultraviolet light exposure
  2. Human Papillomavirus
  3. Coal tar derivative exposure
  4. Cigarette smoking
  5. Chemical carcinogens
  • Signs
  1. Characteristics
    1. First
      1. Red to skin-colored firm, round Papule
      2. Rapid growth into dome-shaped Nodule
        1. May reach up to 1-2 cm in size within weeks to months
      3. Central umbilicated keratinous core
      4. Smooth surface
    2. Later (after 4-6 months)
      1. Lesion regresses over months
      2. Keratin core expelled
      3. Hypopigmented scar remains
  2. Distribution (sun-exposed areas)
    1. Face
    2. Extremities
  • Differential Diagnosis
  1. Squamous Cell Skin Cancer
    1. Similar grossly and histologically to Keratoacanthoma
  • Labs
  • Biopsy
  1. Biopsy lesions suspicious for Squamous Cell Skin Cancer (especially larger lesions)
    1. Exam and pathology findings can not always reliably distinguish keratocanthoma from SCC
    2. Complete excision with 3-5 mm margins is preferred overall
    3. Punch Biopsy is preferred over Shave Biopsy (depth may be inadequate otherwise)
  • Management
  1. Small Keratoacanthoma
    1. Electrodessication and Curettage
    2. Blunt Dissection
  2. Larger Keratoacanthoma
    1. Excision with 3-5 mm margins
    2. Moh's Surgery for difficult areas (esp. in regions with cosmetic concerns)
  3. Other options (non-surgical candidates, multiple lesions, inoperable skin sites)
    1. Topical agents
      1. 5-Fluorouracil 5% cream
        1. Apply during rapid growth tid
        2. Use under tape Occlusion
        3. Effective in 1-6 weeks
      2. Podophyllum 25% in benzoin
        1. Remove central crust and apply every 2 weeks prn
        2. Apply in clinic only due to high concentration
    2. Intralesional injections during rapid growth phase
      1. 5-Fluorouracil intralesional injection
      2. Methotrexate intralesional injection
      3. 5-Interferon alfa-2a injection
    3. Oral agents (for multiple lesions)
      1. Isotretinoin (Accutane)
    4. Radiotherapy
      1. Indicated for difficult cosmetic areas