Basal Cell Carcinoma of the Skin Generalities

Figure 1
Shoulder basal cell carcinoma
  • Basal cell carcinomas (BCCs) are believed to arise from the basal layer of epidermis and its appendages;
    • Since they arise from hair follicles:
      • Most lesions are found on sun-exposed areas of hair-bearing skin
  • These tumors tend to grow slowly:
    • But when left untreated can lead to invasion of local structures, including:
      • Muscle, cartilage, and bone
  • Although BCC is characterized by local and sometimes destructive invasiveness:
    • Metastasis is rare:
      • Occurring in less than 0.05% of cases
  • A number of risk factors are associated with the development of BCC:
    • Ultraviolet (UV) solar radiation is considered to be a significant risk factor:
      • Development is thought to arise from intense, intermittent sun exposure:
        • Leading to burns
      • BCC tends to occur in the head and neck area
    • BCC tends to occur in the treatment field of previous radiation therapy (RT):
      • Specially at a young age
    • Settings of immunosuppression, such as:
      • Organ transplantation, HIV infection, or long-term glucocorticoid:
        • Increase the incidence of BCC
  • Anatomic location within the high-risk “H zone” or “mask area” of the face and size are:
    • Risk factors for BCC recurrence and metastasis
Figure 2
Patient with locally advanced basal cell carcinoma of the back.
  • Extensive research has led to advances in understanding the genetics of BCC:
    • The sonic hedgehog pathway plays a crucial role in the pathogenesis of BCC:
      • Mutations in this pathway have been implicated in the development of disease
    • Mutations in the PTCH1 (patched 1) gene on chromosome 9q:
      • Which codes for the sonic hedgehog receptor:
        • Are present in 30% to 90% of sporadic BCCs
  • Patients with genetic syndromes, including:
    • Xeroderma pigmentosum, albinism, Muir-Torre syndrome, Fanconi anemia, nevoid basal cell carcinoma syndrome or Gorlin syndrome, and Li-Fraumeni syndrome:
      • Have an increased incidence of squamous cell carcinoma (SCC) and BCC

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