Hyperplasia

Keratoacanthoma

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Keratoacanthoma

  • See Also
  1. Common Benign Skin Growths
  • Epidemiology
  1. Onset later in life (mean 64 years old)
  2. More common in men
  • 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: Initial
    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. Characteristics: Later (after 4-6 months)
    1. Lesion regresses over months (up to 12 months)
    2. Keratin core expelled
    3. Hypopigmented scar remains
  3. Distribution (sun-exposed areas)
    1. Face
    2. Extremities
    3. Trunk
  • 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. Skin biopsy AND
    2. Destructive measures
      1. Electrodessication and Curettage
      2. Intralesional Chemotherapy (e.g. Fluorouracil, Methotrexate)
  2. Larger Keratoacanthoma
    1. Excision with 5 mm margins
    2. Moh's Surgery Indications
      1. Deep Lesions
      2. Cosmetic concerns
      3. Diffult surgical sites (central face, ear, nose, perioral, periocular)
  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
  • References
  1. Habif (1996) Dermatology, Mosby-Year, p. 638
  2. Higgins (2015) Am Fam Physician 92(7): 601-7 [PubMed]
  3. Luba (2003) Am Fam Physician 67(4):729-37 [PubMed]