Merkel cell carcinoma: Who gets and causes

Who gets Merkel cell carcinoma?

Most Merkel cell cancers are diagnosed in people who are:

  • 50 years of age or older (90%).
  • Fair skinned and did not protect their skin from the sun (98%).

According to research studies, gender also seems to play a role. Men are twice as likely to get to MCC.

White men who are 50 years of age or older and have spent a lot of time in the sun without sun protection seem to have the greatest risk of developing MCC.

Other risk factors

Anything that increases your risk of getting a disease is a risk factor. Age, fair skin, and lots of sun exposure are the most common risk factors for MCC. Other risk factors for MCC are: 

Illness that weakens your immune system: Your immune system helps you stay healthy. Some illnesses, however, weaken your immune system. Illnesses that weaken the immune system include HIV and chronic lymphocytic leukemia (a cancer of the blood and bone marrow).

Medicine that weakens your immune system: People who received an organ transplant must take medicine for life. This medicine prevents the body from rejecting the transplanted organ. It also weakens the immune system. Other medicines can also weaken the immune system.
If you have concerns about a medicine you take, talk with your doctor. Immediately stopping a medicine or reducing the amount of medicine you take can cause serious side effects.Exposure to arsenic or infrared light: Being exposed to arsenic for a long time seems to increase the risk. Long-term exposure can come from drinking well water that contains arsenic. Some people are exposed to arsenic in the workplace. Infrared light is common in some workplaces and homes. Common sources of infrared light are lasers, some furnaces, and heat lamps.

PUVA therapy, using methoxsalen (meth-OX-a-len): Some patients treated with PUVA therapy receive a medicine called methoxsalen. In one study, researchers found that 3 of the 1,380 patients taking methoxsalen developed MCC. The cancer developed many years later. All of the patients had taken methoxsalen during their PUVA therapy. Two of these patients received more than 300 PUVA treatments.

What causes Merkel cell carcinoma?

Scientists are still studying what causes this skin cancer.

A research breakthrough came in 2008 when scientists discovered a virus called the Merkel cell polyomavirus. This virus is found in many Merkel cell tumors. To gain a better understanding of this cancer, scientists are studying this virus.

If you have risk factors for Merkel cell carcinoma

Having risk factors does not mean that you will get MCC. This skin cancer is rare. You can reduce your risk by protecting your skin from the sun. This can also reduce your risk for getting other types of skin cancer.

If you are concerned that you may have MCC, you should immediately make an appointment to see a dermatologist. You can find out how this skin cancer is diagnosed and treated by going to Merkel cell carcinoma: Diagnosis and treatment.

Learn more about Merkel cell carcinoma:


Bichakjian CK, Alam M, Andersen J, et al. “Merkel cell carcinoma: Clinical practice guidelines in oncology.” National Comprehensive Cancer Network. Version 2.2013.

Feng H, Shuda M, Chang Y, et al. “Clonal integration of a polyomavirus in human Merkel cell carcinoma.” Science 2008; 319:1096-100.

Heath M, Jaimes N, Lemos BD, et al. “Clinical characteristics of Merkel cell carcinoma at diagnosis in 195 patients: the AEIOU features.” J Am Acad Dermatol 2008; 58:375-81.

Lemos BD, Storer BE, Iyer JG, et al. “Pathologic nodal evaluation improves prognostic accuracy in Merkel cell carcinoma: analysis of 5823 cases as the basis of the first consensus staging system.” J Am Acad Dermatol 2010; 63:751-61.

Lunder EJ, Stern RS, “Merkel-cell carcinomas in patients treated with methoxsalen and ultraviolet A radiation.” (Letters to the editor). N Engl J Med. 1998; 339:1247-8.

Reisinger DM, Shiffer JD, Cognetta AB, et al. “Lack of evidence for basal or squamous cell carcinoma infection with Merkel cell polyomavirus in immunocompetent patients with Merkel cell carcinoma.” J Am Acad Dermatol 2010; 63:400-3