Basal Cell Carcinoma
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Incidence in the US: ~1,000,000 cases/year and is increasing about 10% each year
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.
Rare in children, but childhood sun exposure is important in adult disease.
Worldwide, the most common form of cancerIncidence
- 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%
- 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
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 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)
- 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).
- 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.