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

• Greater frequency in geriatric patients (ages 55–75 years have 100× incidence compared with those aged <20)
• The incidence is rapidly increasing in those 20–40 years.

Pediatric Considerations
Rare in children, but childhood sun exposure is important in adult disease.

Epidemiology

Worldwide, the most common form of cancer

• Incidence in the US: 1,000,000 cases/year; increasing about 10% each year
• Predominant age: Generally >40; incidence increasing in younger populations
• Predominant sex: Male > Female (although incidence is increasing in females)
• Lifetime risk of white North Americans: 30%

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:
  • 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
• 3–4 decades after chronic arsenic exposure
• 2 decades after therapeutic radiation
• Chronic immunosuppression: Transplant recipients (10× higher incidence), patients with HIV or lymphomas

• Albinism (recessive alleles)
• Xeroderma pigmentosum (autosomal recessive)
• Bazex syndrome (rare, x-linked dominant)
• Nevoid BCC syndrome/Gorlin syndrome (rare, autosomal-dominant)
• Cytochrome P-450 CYP2D6 and glutathione S-transferase detoxifying enzyme gene mutations (especially in truncal BCC, marked by clusters of basal cell carcinomas and a younger age of onset)

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 and 4 and wearing wide-brimmed hats and long-sleeved shirts.
• Avoid tanning and sunburns (including tanning salons).

Pathophysiology

• UV-induced inflammation and cyclooxygenase activation in skin
• Mutation of PTCH1 (patched homolog 1), a tumor-suppressor gene that inhibits the hedgehog signaling pathway
• Mutation of the SMO (smoothened homolog) gene, which is also involved in the hedgehog signaling pathway
• UV-induced mutations of the TP53 (tumor protein 53), a tumor-suppressor gene
• Activation of BCL2, an antiapoptosis protooncogene

Commonly Associated Conditions

• Cosmetic disfigurement since 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.