Skin cancer is the most common type of cancer. Most skin cancers start in the outer layer of the skin (epidermis). In some cases, they can spread to other parts of the body.
The two main types of nonmelanoma skin cancer are:
Basal cell carcinoma: This is the most common type, which accounts for 75% of all nonmelanoma skin cancer. It can invade normal skin tissue and damage deeper tissues, such as muscles and bones, and affect the appearance of the skin. Basal cell carcinoma very rarely spreads (metastasizes) to other parts of the body.
Squamous cell carcinoma: Accounts for about 20% of all nonmelanoma skin cancer. It usually grows slowly and often develops in injured or diseased skin areas. It is more invasive than basal cell and can spread to other areas of the body.
More than 1 million cases of skin cancer are diagnosed in the United States each year; more than 95% of these are nonmelanoma skin cancer.
Nonmelanoma skin cancer is usually caused by overexposure to the sun and its ultraviolet (UV) rays. Overexposure to UV rays can result from:
- Having severe sunburns and blistering, especially during childhood.
- Spending extensive time in the sun over many years.
- Using tanning beds or sunlamps, which are artificial sources of UV rays.
- Any change on the skin, especially a change in the size or color of a mole or other darkly pigmented growth or spot
- Scaliness, oozing, bleeding, or change in the appearance of a bump or nodule
- Spread of pigmentation beyond its border
- Change in sensation
- Excessive exposure to ultraviolet radiation
- Fair complexion
- Occupational exposure to coal tar, pitch, creosote, arsenic compounds, or radium
- Family history
- Multiple nevi (moles) or atypical nevi