The Biology Of Skin Cancer

What is cancer of the skin? It is a proliferation or growth of abnormal cells in the skin. These cells form tumors or lesions in the skin. Eventually, the cancer cells can spread or metastasize to other parts of the body. Most cases of skin cancer are caused by damage to the skin due to sun exposure.

UVA and UVB Radiation

An understanding of the composition and effects of sunlight helps to explain skin cancer biology. The sun produces ultraviolet (UV) radiation. The atmosphere filters out some of this radiation before it reaches the Earth’s surface but some radiation passes through the atmosphere and it can affect skin growth and development.

Radiation falls into two categories:

  • UVA radiation is not filtered by the atmosphere and its levels remain constant throughout the day. UVA radiation can cause changes in melanin pigment levels (tanning) and skin damage in the deeper levels of skin, contributing to skin cancers.
  • UVB radiation is filtered in part by the atmosphere. It causes skin damage in the superficial skin layers and manifests as tanning, wrinkles and burning. UVB radiation levels are strongest at midday.

UVA and UVB radiation are absorbed by the cells in skin tissue. This can eventually lead to changes in the skin. Melanin pigment increases, which causes tanning. These types of radiation can cause both thickening of the skin and damage to connective tissue. Sun damage accumulates over time, which is why older people are at higher risk of developing some types of skin cancer.

Different levels of exposure are associated with different types of skin cancer. Occasional exposure throughout the lifetime is associated with basal cell carcinoma and melanoma. Persistent long-term exposure is more closely connected with squamous cell carcinoma.

UV Radiation Damages DNA

UV radiation can damage genes that are responsible for inhibiting the replication of damaged or abnormal cells. If these genes are damaged, cancer cells grow unchecked, forming cancerous tumors or lesions.

The relationship between UV rays and melanoma is less clear. Some research suggests that UVA rays may contribute to melanoma. If so, sun exposure is particularly dangerous in this case because not all sunscreens offer protection against UVA rays.

Other Contributing Biological Causes of Skin Cancer

Other factors can be contributing causes of cancer of the skin. In a small number of cases, a genetic predisposition can increase the risk for developing skin cancer. Genetic mutations can be passed from parent to child and, combined with environmental factors such as sun exposure, increase the likelihood of abnormal cell growth.

Certain substances can increase photosensitivity, which is susceptibility to sun damage. Read the labels on medication carefully to find out whether a particular drug or chemical contributes to photosensitivity.


American Cancer Society. (n.d.). Skin cancer prevention and early detection. Retrieved June 21, 2010, from

Canadian Centre for Occupational Health and Safety. (2010). Skin cancer and sunlight. Retrieved June 21, 2010, from

National Science Foundation Polar Programs UV Monitoring Network. (2001). Effects of UV radiation on you. Retrieved June 21, 2010, from

The Skin Cancer Foundation. (2010). Understanding UVA and UVB. Retrieved June 21, 2010, from