Basal Cell Carcinoma
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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
Greater frequency in geriatric patients (Ages 55 to 75 years have 100 times the incidence when compared with those aged <20 years.)
- 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.
Worldwide, the most common form of cancer
- Incidence in the United States: 1.2 million cases each year; 4 to 5 times more common than squamous cell carcinoma; 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
- 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
- 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
- After initial diagnosis of skin cancer, 35% risk of new nonmelanoma skin cancer at 3 years and 50% at 5 years
- Family history of skin cancer
- 3 to 4 decades after chronic arsenic exposure
- 2 decades after therapeutic radiation
- 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
- 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.