Skin Cancer: Basal and Squamous Cell

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Causes, Risk Factors, and Prevention TOPICS

What are the risk factors for basal and squamous cell skin cancers?

A risk factor is anything that affects your chance of getting a disease such as cancer. Different cancers have different risk factors. Some risk factors, like smoking and excess sun exposure, can be changed. Others, like a person’s age or family history, can’t be changed.

But having a risk factor, or even many risk factors, does not mean that you will get the disease. And some people who get the disease may have few or no known risk factors.

The following are known risk factors for basal cell and squamous cell carcinomas. (These factors don’t necessarily apply to some other forms of skin cancer, such as Kaposi sarcoma and skin lymphoma.)

Ultraviolet (UV) light exposure

Exposure to ultraviolet (UV) rays is thought to be the major risk factor for most skin cancers. Sunlight is the main source of UV rays. Tanning beds are another source of UV rays.

While UV rays make up only a very small portion of the sun’s rays, they are the main cause of the damaging effects of the sun on the skin. UV rays damage the DNA of skin cells. Skin cancers begin when this damage affects the DNA of genes that control skin cell growth.

To learn more about the effects of UV rays on the skin and what you can do to protect yourself and your loved ones, see Skin Cancer Prevention and Early Detection.

Having light-colored skin

Whites have a much higher risk of skin cancer than African Americans or Hispanics. This is because the skin pigment melanin has a protective effect in people with darker skin. Whites with fair (light-colored) skin that freckles or burns easily are at especially high risk. This is one of the reasons Australia, where many people descend from fair-skinned immigrants from the British Isles, has the highest rate of skin cancer in the world.

Albinism is an inherited lack of protective skin pigment. People with this condition may have pink-white skin and white hair. They have a high risk of getting sunburns and skin cancer, so they need to be careful to protect their skin.

Older age

The risk of getting basal and squamous cell skin cancers rises as people get older. This is probably because of the buildup of sun exposure over time. These cancers are now being seen in younger people as well, probably because they are spending more time in the sun with their skin exposed.

Male gender

Men are about twice as likely as women to have basal cell cancers and about 3 times as likely to have squamous cell cancers of the skin. This is thought to be due mainly to getting more sun exposure.

Exposure to certain chemicals

Exposure to large amounts of arsenic increases the risk of developing skin cancer. Arsenic is an element found naturally in well water in some areas. It’s also used in making some pesticides and in some other industries.

Workers exposed to coal tar, paraffin, and certain types of oil may also have an increased risk of skin cancer.

Radiation exposure

People who have had radiation treatment have a higher risk of developing skin cancer in the area that received the treatment. This is particularly a concern in children who have had radiation treatment for cancer.

Previous skin cancer

Anyone who has had a basal or squamous cell cancer has a much higher chance of developing another one.

Long-term or severe skin inflammation or injury

Scars from severe burns, areas of skin over serious bone infections, and skin damaged by some severe inflammatory skin diseases are more likely to develop skin cancers, although this risk is generally small.

Psoriasis treatment

Psoralens and ultraviolet light (PUVA) treatments given to some patients with psoriasis (a long-lasting inflammatory skin disease) can increase the risk of developing squamous cell skin cancer and probably other skin cancers.

Xeroderma pigmentosum (XP)

This very rare inherited condition reduces the ability of skin cells to repair DNA damage caused by sun exposure. People with this disorder often develop many skin cancers, starting in childhood.

Basal cell nevus syndrome (also known as nevoid basal cell carcinoma syndrome or Gorlin syndrome)

In this rare congenital (present at birth) condition, people develop many basal cell cancers over their lifetime. People with this syndrome may also have abnormalities of the jaw (and other bones), eyes, and nervous tissue.

Most of the time this condition is inherited from a parent. In families with this syndrome, those affected often start to develop basal cell cancers as children or teens. Exposure to UV rays can increase the number of tumors these people get.

Weakened immune system

The immune system helps the body fight cancers of the skin and other organs. People with weakened immune systems (from certain diseases or medical treatments) are more likely to develop many types of skin cancer, including squamous cell cancer, melanoma, and less common types such as Kaposi sarcoma and Merkel cell carcinoma.

For example, people who get organ transplants are usually given medicines that weaken their immune system to help prevent their body from rejecting the new organ. This increases their risk of developing skin cancer. The rate of skin cancer in people who have had transplants can be as high as 70% within 20 years after the transplant. Skin cancers in people with weakened immune systems tend to grow faster and are more likely to be fatal.

Treatment with large doses of corticosteroid drugs can also weaken the immune system. This may also increase a person’s risk of skin cancer.

People infected with HIV, the virus that causes AIDS, often have weakened immune systems and also are at increased risk for basal and squamous cell cancers.

Human papilloma virus (HPV) infection

Human papilloma viruses (HPVs) are a group of more than 150 viruses that can cause papillomas, or warts. The warts that people commonly get on their hands and feet are not related to any form of cancer. But some HPV types, especially those that affect the genital and anal areas and the skin around the fingernails, seem to be related to skin cancers in these areas.


People who smoke are more likely to develop squamous cell skin cancer, especially on the lips. Smoking is not a known risk factor for basal cell cancer.

Last Medical Review: 04/02/2015
Last Revised: 04/03/2015