A healthy living blog from Marshfield Clinic Health System

What is Merkel cell carcinoma? 3 things to know

Merkel cell carcinoma (MCC) is a rare and aggressive form of skin cancer that is found in Merkel cells, which are cells found in the top layer of skin. MCC is relatively rare, accounting for only about 1% of all skin cancers. It has a higher mortality rate compared to other types of skin cancer.

Woman and daughter standing together talking about merkel cell carcinoma.

Merkel cell carcinoma is a rare and aggressive type of skin cancer.

“Merkel cell carcinoma is a very aggressive and rapidly growing form of skin cancer that requires prompt treatment,” said Dr. Rohit Sharma, surgical oncologist at Marshfield Clinic Health System. “It is important for patients to be aware of the signs and symptoms of MCC, which can include a small, painless nodule on the skin, changes in the size or appearance of a mole and a sore that does not heal.”

MCC typically appears on the skin, but it can also occur in the mouth, anus or genital area.


The exact cause of MCC is not fully understood. It is believed to be related to UV exposure, immune suppression and certain types of viruses.

MCC is more common in older adults and people with a weakened immune system. It’s also more common in those with a history of sun exposure and sunburns.

One factor that has been linked to the development of MCC is infection with certain types of viruses, including the polyoma virus. Polyoma viruses are a group of viruses that can infect both humans and animals and can cause a variety of diseases.

“According to research, approximately 80% of MCC cases are associated with infection with the polyoma virus,” Dr. Sharma said. “The virus is thought to cause genetic changes in the cells that lead to the development of MCC.”

In addition, infection with the polyoma virus has been linked to a worse prognosis for MCC patients, with a higher risk of recurrence and a lower survival rate.

The polyoma virus is primarily spread through contact with bodily fluids, such as blood, urine and saliva. It can also be spread through close personal contact, such as touching or kissing.

While the virus is relatively common, the risk of developing MCC as a result of polyoma virus infection is low. However, individuals who have a weakened immune system, such as those with HIV/AIDS or those who have received an organ transplant, are at a higher risk of developing MCC as a result of polyoma virus infection.


Treatment for MCC typically involves surgical removal of the tumor, followed by radiation therapy and/or chemotherapy. The type of treatment depends on the stage and location of the cancer, as well as the patient’s overall health.

It is important for patients with MCC to be followed closely by their health care team. Cancer can recur even after treatment.

“If you notice any changes in your skin or have a sore that does not heal, it is important to see a dermatologist or oncologist right away,” Dr. Sharma said. “Early detection is key to successful treatment of MCC.”

Ongoing study

Marshfield Clinic Health System has a multidisciplinary tumor board where medical oncologists, radiation oncologists, pathologists, medical geneticists, radiologists and surgical oncologists participate and discuss the management of the disease.

The Health System has been designated as Merkel Cell Treatment Center of Excellence by merkelcell.org. This is an organization of internationally-respected physicians and researchers whose work is funded by the National Institute of Health, American Cancer Society and National Cancer Institute.

Marshfield Clinic Research Institute has a number of clinical trials open and currently recruiting for advanced Merkel cell carcinoma study. Click here to learn more information.

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