Merkel Cell Carcinoma: Causes, Symptoms, and Treatment
Medically reviewed by Achuta Uppu, MD, Internal Medicine. Last reviewed: October 23, 2026.
What kind of doctor treats Merkel Cell Carcinoma?
A dermatologist (a skin doctor) often diagnoses Merkel cell carcinoma. Care involves a team that may include a medical oncologist (a cancer drug doctor), a surgical oncologist (a cancer surgeon), and a radiation oncologist. A direct primary care or concierge doctor can be a first stop for an evaluation and can refer you to a specialist when needed.
What is Merkel cell carcinoma?
Merkel cell carcinoma is a very rare type of skin cancer. It forms when Merkel cells grow out of control. Merkel cells are found in the top layer of the skin, very close to nerve endings that receive the sensation of touch.
It tends to grow quickly and to spread early. It usually spreads first to nearby lymph nodes. Later it may spread to lymph nodes or skin far away, or to the lungs, brain, bones, or other organs. It is the second most common cause of skin cancer death after melanoma.
Symptoms
Merkel cell carcinoma usually shows up as a single lump on sun-exposed skin.
- Fast-growing.
- Painless.
- Firm and dome-shaped or raised.
- Red or violet in color.
It most often starts on sun-exposed skin, especially the head and neck, but it can also start on skin that is not usually in the sun. The lump often causes no symptoms. Sometimes it opens up and forms a sore with a crust. Lymph nodes near the lump can swell, which is a sign the cancer may have spread to them.
Causes and who gets it
Risk factors include a lot of time in natural sunlight or artificial sunlight, such as tanning beds. A weak immune system also raises risk. This can come from a disease such as chronic lymphocytic leukemia or HIV infection, or from medicine taken after an organ transplant. Other risk factors are a history of other types of cancer and being older than 50, male, or White. Not everyone with these risk factors gets Merkel cell carcinoma, and it can develop in people with no known risk factors.
A common virus called Merkel cell polyomavirus is often linked to the cancer, in about 80 percent of cases. Most people are infected with it by adulthood, and it usually causes no symptoms.
How doctors diagnose it
The doctor asks about your health history and does a physical exam. A full-body skin exam checks for bumps or spots that look abnormal in color, size, shape, or texture. A skin biopsy removes a small piece of skin so a pathologist, a doctor who studies tissue, can look for cancer under a microscope.
More tests find out whether the cancer has spread. This is called staging. These tests may include CT scans, PET scans, and a lymph node biopsy. In a sentinel lymph node biopsy, the first lymph node the cancer is likely to reach is removed and checked for cancer cells.
Treatment
You and your cancer care team decide on a plan together. It may include more than one type of treatment. The stage of the cancer, your overall health, and your preferences all matter.
For cancer that has not spread, surgery is recommended to remove the tumor. Usually the tumor is removed along with some healthy skin around it, which is called wide local excision. Nearby lymph nodes may also be removed. Some people get radiation therapy after surgery to lower the risk that the cancer will come back. Radiation can also be the main treatment when surgery is not possible.
Immunotherapy helps a person's immune system fight cancer. It is used for stage IV cancer. Drugs include avelumab, pembrolizumab, and retifanlimab. Chemotherapy is no longer recommended as the first medicine for spread cancer in people who can have immunotherapy. Treatment can cause side effects, so ask your care team what to expect. Follow-up visits and tests are needed after treatment.
When to see a doctor
Check with your doctor if you see changes in your skin. Show your doctor any lump that is firm, painless, and growing fast. Swollen lymph nodes near a skin lump can mean the cancer has spread, so they also need to be checked.
After treatment, it is common for the cancer to come back, so tell your doctor about any new skin changes.
How a direct primary care or concierge doctor fits in
A direct primary care doctor charges a flat monthly fee instead of billing insurance, while a concierge doctor usually charges more and often works alongside insurance. Either type of doctor can check a new skin lump and refer you to a dermatologist or cancer team. They can also help coordinate care and follow-up between your specialists.
Common questions
Is Merkel cell carcinoma dangerous?
Yes, it can be serious. It tends to grow quickly and to spread early, and it is the second most common cause of skin cancer death after melanoma.
Is Merkel cell carcinoma common?
No, it is very rare. It is a type of skin cancer that forms when Merkel cells grow out of control.
Can Merkel cell carcinoma come back after treatment?
Yes, it is common for Merkel cell carcinoma to come back after treatment. If it comes back, it may return in the skin, lymph nodes, or other parts of the body.
Does sun exposure raise the risk of Merkel cell carcinoma?
Yes, being exposed to a lot of natural sunlight is a risk factor. So is artificial sunlight, such as from tanning beds.
Is immunotherapy used for Merkel cell carcinoma?
Yes, immunotherapy is used to treat it. Most people with spread or returning cancer are recommended to have it.
Sources
- National Cancer Institute - Merkel Cell Carcinoma Treatment (PDQ) Patient Version
- NORD - Merkel Cell Carcinoma
Medical Disclaimer
This content is for general educational and informational purposes only and is not medical advice. It is not a substitute for professional medical advice, diagnosis, or treatment, and reading it does not create a doctor-patient relationship. Always seek the advice of your physician or another qualified health provider with any questions about a medical condition, and never disregard or delay seeking professional advice because of something you read here. If you think you may have a medical emergency, call 911 (or your local emergency number) immediately.
