What is Skin Cancer (Basal Cell Carcinoma of the Skin)

Basal Cell Carcinoma of the Skin is a cancer of the skin.

The skin is the largest organ of the body. It serves as a protective barrier between us and the environment, keeping water in and infection out. The skin in composed of two main layers:

  • The epidermis – consisting of keratinised stratified squamous epithelium; and
  • The dermis – a dense connective tissue.

Epidermal components of the skin include hair follicles and hair; sweat, sebaceous and mammary glands; and nails.

The functions of the skin include:

  • Providing a protective barrier from the external environment;
  • Homeostasis – assisting in the regulation of body temperature and water loss;
  • Sensory function – providing information about the external environment;
  • Excretion of body fluids – sweating; and
  • Synthesis of vitamin D on exposure to sunlight.

In addition, cells in the deep part of the epidermis make melanin to protect us from ultraviolet radiation. From a cancer viewpoint, the most important cells in the epidermis are squamous cells, basal cells and melanocytes.

Basal Cell Carcinoma of the Skin

Statistics on Skin Cancer (Basal Cell Carcinoma of the Skin)

Basal cell carcinoma is the most common form of skin cancer, accounting for more than 75% of all skin malignancies and occurs with increasing age and with sex incidence being almost twice as common in males.

Geographically, the basal cell carcinoma tumour is found worldwide, but with striking geographical variation, with incidence decreasing with increasing distance from the equator. Basal cell carcinomas are more common in regions with high levels of sunlight.

Risk Factors for Skin Cancer (Basal Cell Carcinoma of the Skin)

The most important predisposing factor in the development of basal cell carcinoma is the exposure to ultraviolet radiation (UVB) in sunlight. Chronic exposure to sunlight is associated with premature aging, blunting of the immunological responses of the skin to environmental antigens and the development of premalignant and malignant neoplasms.

However, there are also important genetic contributions to the development of basal cell carcinoma. Risk factors relating to exposure and susceptibility to sunlight include: fair skin, Northern European ancestry, childhood freckling and number of past sunburns. The type, timing, and quantity of sun exposure associated with an increased risk in the development of BCC have not yet been fully defined.

With basal cell carcinoma it is currently believed that it is childhood sun exposure rather than cumulative sun exposure that is the main aetiological factor in the development of BCC in later life. In addition, short periods of intense sun exposure are thought to be more dangerous than chronic exposure to a similar total dose.

Other predisposing factors with basal cell carcinoma include:

Ionising radiation, chemical carcinogens such as arsenic, chronic immunosuppression (incidence of squamous cell carcinoma much greater than that of BCC), and rare genetic conditions such as xeroderma pigmentosa and basal cell naevus syndromes.

The genetic bases for these syndromes have played an important role in the investigation of the molecular pathogenesis of BCC, with the discovery of mutations in the tumour suppressor region of the PTCH gene on chromosome 9 being found in the inherited and sporadic cases of basal cell carcinoma .

Progression of Skin Cancer (Basal Cell Carcinoma of the Skin)

The basal cell carcinoma tumour spreads by local extension. Basal cell carcinoma is a malignant tumour but metastatic spread is rare (less than 0.1%) even in advanced cases. Basal cell carcinoma typically occurs as a very slow growing lesion that can, in very advanced cases, become ulcerated and infiltrate surrounding structures such as bone or facial sinuses.

How is Skin Cancer (Basal Cell Carcinoma of the Skin) Diagnosed?

General investigations may show no abnormality.

Prognosis of Skin Cancer (Basal Cell Carcinoma of the Skin)

Basal cell carcinoma is associated with an excellent prognosis. Even with late stage diagnosis cure is almost invariable with appropriate intervention. Although mortality for basal cell carcinoma is exceedingly low, advanced lesions can be associated with significant morbidity – in terms of disfigurement through local invasion and wound care difficulties in lesions that are extensively ulcerated. In the very few cases of metastatic basal cell carcinoma that have been described, death usually occurs within 8 months.

How is Skin Cancer (Basal Cell Carcinoma of the Skin) Treated?

Optimal treatment for a given basal cell carcinoma depends upon both its size and location. Techniques can include cryosurgery, electrodessication and curettage, radiation therapy, topical 5-fluorouracil, surgical excision, or Mohs micrographic surgery – all of which are associated with very high rates of cure when selected appropriately by the treating specialist and individually suited to the basal cell carcinoma patients needs.

Most commonly, basal cell carcinoma treatment decisions are between radiotherapy and surgical excision, with surgical excision being the preferred treatment for almost all basal cell carcinomas.

For superficial BCC, topical 5-fluorouracil applied twice daily can be effective after 2-12 weeks and has a high cure rate. Its use in invasive tumours is not established. Iquimod 5% cream is effective in the treatment of superficial BCs and Bowen’s disease, however its role in the treatment of other basal cell carcinoma is still under investigation.

The use of adjuvant systemic chemotherapy in BCC is in the research phase and is not currently part of routine management of BCC.

Improvement in basal cell carcinoma symptoms is an important measurement. Specific monitoring may be by clinical follow-up to detect recurrence or the appearance of new primary lesions. This should include visual inspection and palpation for any deeper recurrence, as well as questioning the patients about any altered sensation in the area of the lesion.

Almost 40% of patients with a single basal cell carcinoma will have a second primary within 5 years of the discovery of the initial tumour – so detailed and ongoing follow-up of all patients is very important.

The Basal cell carcinoma symptoms that may require attention are somatic pain from bony infiltration and neurogenic pain if nerve tissue is compressed. Wound care is important in basal cell carcinoma patients with advanced and ulcerative disease.

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Skin Cancer (Basal Cell Carcinoma of the Skin) References

For more information visit our Lifestyle/Preventative Page on Cancer and UV Radiation.