Basal Cell Carcinoma

Skin cancer is the most prevalent type of cancer in human beings and occurs in three main forms: melanoma, basal cell carcinoma and squamous cell carcinoma. Each of these takes its name from the type of skin cell in which it originates. The latter two, basal cell carcinoma and squamous cell carcinoma, are often referred to as non-melanoma skin cancers.

Basal cell carcinomas are malignant tumors that originate in the basal cells lining the inner part of the epidermis. They are the most common form of skin cancer, accounting for 75% of all diagnosed cases. It is estimated that about one million new cases are diagnosed in the US each year. This type of skin cancer usually appears on areas of the skin most exposed to the sun (head, face, neck, hands and arms).

Regular exposure to the ultraviolet (UV) rays of the sun increases the risk of developing all types of skin cancer, including basal cell carcinoma. Exposure to UV rays from the sun is mainly dependent on how far away from the equator one lives. In the far north (e.g. in places such Iceland, Finland and Alaska) there is relatively little UV radiation from the sun and the risk of too much exposure is low, whereas those living in northern Australia, Florida, India and Ethiopia are much more highly exposed. Exposure to UV radiation on tanning beds also increases the risk of developing basal cell carcinoma.

Given the same level of exposure to UV radiation as people with a dark complexion, individuals with pale skin, with red or blonde hair and blue or green eyes and who are tan-resistant and burn easily are particularly at risk of developing basal cell carcinoma. This is thought to be due to the fact that a light complexion provides less protection from UV radiation than a dark complexion. Because skin, hair and eye color are by and large genetically determined, the risk of developing basal cell carcinoma from UV radiation exposure therefore results from a mixture of genetic and environmental factors. However, there are also genetic risk factors for basal cell carcinoma that appear to act independently of exposure to UV radiation.

Scientists at deCODE genetics have identified genetic variants that confer a significant risk of developing basal cell carcinoma in people of European descent. Two variants are located on chromosome 1 and one variant on each of the following chromosomes; 5, 7, 9, and 12. These variants are not known to affect the hair, eye and skin color traits that are associated with poor UV protection. Therefore they probably represent risk factors that are separate from and therefore additional to UV radiation exposure.

The deCODEme Genetic Scan identifies these six variants and provides an interpretation of the associated risk for the development of basal cell carcinoma for individuals of European descent. At this time risk information is not available for other ethnicities.

This content was last reviewed on February 09, 2010.