The Risks. The Causes. What You Can Do.
Anything that increases your likelihood of developing a disease like Merkel cell carcinoma (MCC) is called a risk factor.
These factors put you at increased risk for the disease. For more information about risk factors, click the links below.
- History of unprotected exposure to ultraviolet (UV) radiation from the sun or indoor tanning.
- Weakened immune system, due to a medical condition or medications.
- History of skin cancer, including basal cell carcinoma (BCC), squamous cell carcinoma (SCC) or melanoma.
- Age: Most people who develop MCC are over 50 years old.
- Gender: Men are more likely to get the disease
- Fair skin: People with fair skin are at greater risk for MCC, but it can affect anyone.
What causes MCC?
Cancers are caused by DNA changes in cells. While scientists and researchers know the risk factors behind Merkel cell carcinoma, they are still working to gain a comprehensive understanding of precisely how these factors lead to the DNA changes that result in the disease. Since MCC does not seem to run in families, these DNA changes most likely happen during the course of a person’s life.
What we do know
UV exposure creates a double threat for MCC
Not only does UV exposure cause damage that increases your skin cancer risk; it also suppresses your immune system. This reduces its ability to repair damage and fight skin cancers and other diseases. No matter the source of UV radiation, there is a clear and dangerous correlation between exposure and MCC.
Immunosuppression and MCC are strongly linked.
If your immune system is persistently weakened or suppressed, you are about 15 times more likely to develop MCC than people with healthy immune systems. However, more than 90 percent of MCC cases arise in people with no known immune problems. Immunosuppression can be caused by:
- Diseases such as HIV and certain cancers including chronic lymphocytic leukemia and lymphomas.
- Immunosuppressant medications used for transplant recipients and for autoimmune diseases including lupus, psoriasis, Crohn’s disease and rheumatoid arthritis.
Immunosuppressed MCC patients often develop the disease at a far younger age; about half of MCCs in these patients occur before age 50.
If your immune system is suppressed, talk to your doctors about your chances of developing MCC, and be sure to protect yourself against other risk factors, especially UV exposure.
A history of skin cancer is also highly associated with Merkel cell carcinoma. If you’ve had melanoma, squamous cell carcinoma, basal cell carcinoma or Bowen’s disease (an early form of SCC) — skin cancers frequently caused by UV exposure — you are more likely to develop MCC.
Merkel cell polyomavirus and MCC
Evidence of the Merkel cell polyomavirus can be found in most, but not all, Merkel cell tumors. The virus, discovered in 2008, lives in the skin of most people, without signs and symptoms, and without ever developing into MCC. Since it’s a very common virus, and since MCC is an extremely rare disease, scientists are still not certain about exactly how or why the virus causes Merkel cell carcinoma in some people. What is clear is that other factors such as UV exposure and immunosuppression also play a role in initiating the growth of MCC tumors.
Sandra D’Angelo, MD
Paul Nghiem, MD, PhD
Last updated: August 2022