Basal Cell Carcinoma

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Description

Basal cell carcinoma (BCC) is the most common type of skin cancer, originating from the basal cell layer of the epidermis and its appendages.

  • Rarely metastasizes but is locally invasive and can cause local tissue destruction and disfigurement, especially in soft tissue, cartilage, and bone

Epidemiology

BCC is the most common cancer in the United States, Europe, and Australia (highest in Australia); similar rates are seen across North America, Europe, and Asia; the most common skin cancer worldwide

Incidence

  • Annual incidence in the United States is estimated to be 4.3 million; 2 times more common than squamous cell carcinoma (SCC)
  • Lifetime risk is ~30% in white populations and ~20% overall.
  • Most common skin cancer in Asian and Hispanic individuals; second most common skin cancer in African American/Black individuals (1). Recent reports suggest an increasing incidence of BCC in Hispanic individuals.
  • Predominant age: generally >60 years
  • Predominant sex: men > women (1.5:1 ratio)

Etiology and Pathophysiology

UV radiation induces inflammation and cyclooxygenase activation in the skin.

Genetics

  • Several genetic conditions increase the risk of developing BCC:
    • Albinism (recessive alleles)
    • Xeroderma pigmentosum (autosomal recessive)
    • Bazex-Dupre-Christol syndrome (rare, X-linked dominant)
    • Nevoid BCC syndrome/Gorlin-Goltz syndrome (rare, autosomal dominant)
    • Cytochrome P450 CYP2D6 and glutathione S-transferase detoxifying enzyme gene mutations (especially in truncal BCC, marked by clusters of BCCs and a younger age of onset)
    • Mutations in the tumor suppressor gene patched, or activated mutations in smoothened, resulting in upregulation of hedgehog pathway signaling
    • Epidermolysis bullosa simplex

Risk Factors

  • Chronic sun exposure (UV radiation); increased susceptibility in the following phenotypes:
    • Light complexion: skin type I (burns, but does not tan) and skin type II (usually burns, sometimes tans)
    • Freckles
    • Red or blond hair
    • Blue or green eyes
  • Tendency to sunburn
  • Prolonged exposure to water, sand, or snow increases UV risk.
  • Male sex; rising risk in women due to tanning beds
  • History of nonmelanoma skin cancer
  • Family history of skin cancer
  • Immunosuppression (e.g., transplant, HIV, lymphoma)
  • Exposure to carcinogenic substances (e.g., arsenic)
  • Xeroderma pigmentosum
  • Photosensitizing medications

General Prevention

  • Use broad-spectrum sunscreens of at least SPF 30 daily at least 15 minutes before outdoor activity. Reapply every 2 hours or after swimming.
  • Avoid sun overexposure and tanning beds. Use physical barriers methods such as protective clothing, hats, and sunglasses.
  • The USPSTF concludes the current evidence is insufficient to assess the balance of benefits and harms of visual skin examination by a clinician to screen for skin cancer in adults. Consensus guidelines recommend a whole-body skin examination every 6 to 12 months for the first 2 years following BCC diagnosis and then at least annually for life.

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