Dermatology Book

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Squamous Cell Carcinoma of the Skin

Aka: Squamous Cell Carcinoma of the Skin, Squamous Cell Skin Cancer, Squamous Cell Carcinoma, Cutaneous Squamous Cell Carcinoma
  1. See Also
    1. Nonmelanoma Skin Cancer
    2. Actinic Keratoses
    3. Basal Cell Carcinoma
  2. Epidemiology
    1. Age-adjusted Incidence: 100-150 per 100,000 persons/year
    2. Gender: Twice as common in males
    3. Incidence in Skin of Color
      1. Ethnicities with SCC as most common skin cancer
        1. Native Americans
        2. Black patients (Peak Incidence at ages 40-49)
      2. Ethnicities with SCC as second most common skin cancer
        1. Chinese and Japanese (peaks after age 60 years old)
        2. Hispanic patients
  3. Risk Factors
    1. See Nonmelanoma Skin Cancer
    2. Exposure to UVB
    3. Organ transplant recipients (65 fold increased risk related to immunosuppression)
    4. Advanced age
    5. Closer distance to the equator
  4. Pathophysiology
    1. Arises from superficial layers of Keratinocytes
      1. Neoplastic transformation is triggered by UV radiation exposure
      2. SCC is on the same spectrum as Actinic Keratoses
        1. Actinic Keratoses proliferate and extend into the Dermis at which point they are defined as SCC
      3. SCC spreads by local infiltration
        1. Spreads along tissue planes and structures such as nerves, arteries and veins
    2. Precursor lesions
      1. Actinic Keratoses (60% of SCC arises from actinics)
      2. Radiation and burn scars
  5. Symptoms
    1. Nonhealing lesion that frequently bleeds without significant Trauma
  6. Signs
    1. Location
      1. Sun exposed areas
    2. Characteristics
      1. Firm, smooth hyperkeratotic Papule, Nodule, patch or Plaque on indurated base
      2. Ulceration and crusting is common
      3. Thick white scale may be present
      4. Fleshy heaped-up edges of lesion
    3. Variants
      1. Verrucous carcinoma
        1. Wart-like SCC lesion with higher malignant potential
      2. Bowen's disease (SCC in-situ)
        1. Slow-growing, scaly red Plaque on sun-exposed skin
      3. Cutaneous horn (keratin horn, cornu cutaneum)
        1. Hyperkeratotic growth with similar appearance to a horn
        2. Starts as Actinic Keratosis and progresses to Squamous Cell Carcinoma
  7. Diagnosis: Skin Biopsy
    1. Raised lesion: Shave Biopsy if not pigmented
      1. Any suspicion of Melanoma needs full-thickness sample
    2. Flat lesions: Punch Biopsy or full excision
  8. Differential Diagnosis
    1. See Nonmelanoma Skin Cancer
    2. Keratocanthoma
  9. Management
    1. Mohs' Microographic Surgery
      1. Preferred as first-line therapy in most cases of Cutaneous Squamous Cell Carcinoma
      2. Indications
        1. Large lesions
          1. Central face, periorbital, periauricular: >6 mm
          2. Cheeks, forehead, neck, scalp: >10 mm
          3. Trunk, extremities: >20 mm
        2. Indistinct margins
        3. Recurrent lesions
        4. Lesion in close proximity to eyes, nose, mouth
        5. Preserve cosmetic appearance
      3. References
        1. Martinez (2001) Mayo Clin Proc 76:1253 [PubMed]
    2. Surgical excision
      1. Complete excision recommended over ED&C
        1. Due to risk of metastases
      2. Imperative to confirm negative margins
      3. Indications
        1. Small lesions less than size criteria for Moh's
        2. Slow growing, well differentiated lesions
        3. Negative for neural or vascular invasion
    3. Radiation Therapy
      1. Indicated in age over 55 years with SCC in high risk, surgically difficult areas
  10. Course
    1. More rapid growth than Basal Cell Carcinoma
    2. Locally destructive skin cancer
    3. Metastases
      1. Ocurs in 3-5% of cases to distant sites via hematogenous spread
      2. Risk factors (may confer up to 40% metastases risk)
        1. Large tumors >2 cm in diameter (3 fold increased risk of metastasis)
        2. Involvement of ear, lip or chronically diseased or injured skin
        3. Immunosuppression
  11. Prevention
    1. See Sun Exposure (lists general preventive measures)
    2. See Sunscreen
  12. References
    1. Habif (2004) Dermatology p. 744-7
    2. Firnhaber (2012) Am Fam Physician 86(2): 161-8 [PubMed]
    3. Stulberg (2004) Am Fam Physician 70:1481-8 [PubMed]

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