Basal Cell Carcinoma

Basal Cell Carcinoma is a topic covered in the 5-Minute Clinical Consult.

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Basics

Description

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

  • Rarely metastasizes but capable of local tissue destruction

Geriatric Considerations
Greater frequency in geriatric patients (Ages 55 to 75 years have 100 times the incidence when compared with those aged <20 years.)

Pediatric Considerations
  • Rare in children, but childhood radiation treatment is contributory, as are frequent or severe sunburns
  • The Centers for Disease Control and Prevention recommends against using tanning beds and lamps in their guidelines for cancer prevention in school-age children.

Epidemiology

Worldwide, the most common form of cancer

Incidence
  • Incidence in the United States: 2 million cases each year; 2.5 times more common than squamous cell carcinoma (SCC); Australia has highest incidence in the world.
  • White people have a 1 in 5 chance of developing BCC during their lifetime.
  • Predominant age: generally >40 years, although incidence increasing in younger populations
  • Predominant sex: male > female (2:1 ratio)

Etiology and Pathophysiology

  • UV-induced inflammation and cyclooxygenase activation in skin
  • In chromosome 9q22, mutation of PTCH1 (patched homolog 1), a tumor-suppressor gene that inhibits the hedgehog signaling pathway
  • UV-induced mutations of the TP53 (tumor protein 53), a tumor-suppressor gene
  • Activation of BCL2, an antiapoptosis proto-oncogene

Genetics
  • Several genetic conditions increase the risk of developing BCC:
    • Albinism (recessive alleles)
    • Xeroderma pigmentosum (autosomal recessive)
    • Bazex syndrome (rare, X-linked dominant)
    • Nevoid BCC syndrome/Gorlin 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

Risk Factors

  • Chronic sun exposure (UV radiation); most common in the following phenotypes:
    • Light complexion: skin type I (burns but does not tan) and skin type II (usually burns, sometimes tans)
    • Red or blond hair
    • Blue or green eyes
  • Tendency to sunburn
  • Male sex, although increasing risk in women due to lifestyle changes, such as tanning beds
  • History of nonmelanoma skin cancer
  • Family history of skin cancer
  • Chronic immunosuppression: transplant recipients (10 times higher incidence), patients with HIV, or lymphomas
  • No significant association between age and recurrence rate, according to most studies

General Prevention

  • Use broad-spectrum sunscreens of at least SPF 30 daily and reapply after swimming or sweating.
  • Avoid overexposure to the sun by seeking shade between 10 AM and 4 PM and wearing wide-brimmed hats and long-sleeved shirts.
  • The American Cancer Society recommends cancer-related checkups every 3 years in patients 20 to 40 years old and yearly in patients >40 years.

Commonly Associated Conditions

  • Cosmetic disfigurement because head and neck most often affected
  • Loss of vision with orbital involvement
  • Loss of nerve function due to perineural spread or extensive and deep invasion
  • Ulcerating neoplasms are prone to infections.

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