Merkel cell carcinoma
Overview
Merkel cell carcinoma is a rare type of skin cancer. It most often appears as a bump on the face, head or neck. Merkel cell carcinoma also is called neuroendocrine carcinoma of the skin.
Merkel cell carcinoma most often happens in people older than 50. Long-term sun exposure or a weakened immune system may raise the risk of getting this cancer.
Merkel cell carcinoma tends to grow fast and to spread quickly to other parts of the body. Treatment may depend on whether the cancer has spread beyond the skin.
Symptoms
The first symptom of Merkel cell carcinoma most often is a growth on the skin. This skin cancer can happen anywhere on the body. It happens most often on skin that typically gets sunlight. In white people, the growth is most likely to be on the head or neck. In Black people, the growth more often is on the legs.
A Merkel cell carcinoma can cause:
Make an appointment with a healthcare professional if you have a mole, freckle or bump that changes size, shape or color. Also see a healthcare professional if you have a bump that grows fast or bleeds easily after minor injury, such as washing your skin or shaving.
Causes
It's often not clear what causes Merkel cell carcinoma.
This skin cancer happens when cells in the skin develop changes in their DNA. A cell's DNA holds the instructions that tell the cell what to do. In healthy cells, the DNA gives instructions to grow and multiply at a set rate. The instructions tell the cells to die at a set time.
In cancer cells, the DNA changes give other instructions. The changes tell the cancer cells to grow and multiply at a fast rate. Cancer cells can keep living when healthy cells would die. This causes too many cells.
The cancer cells might form a mass called a tumor. The tumor can grow to invade and destroy healthy body tissue. In time, cancer cells can break away and spread to other parts of the body. When cancer spreads, it's called metastatic cancer.
Merkel cell carcinoma is named for the cells where experts once thought it started. The Merkel cells are found at the bottom of the outer layer of skin. The Merkel cells are connected to the nerve endings in the skin that play a role in the sense of touch. Healthcare professionals no longer believe that this cancer starts in the Merkel cells. They don't know exactly what kind of cells it starts in.
It's often not clear what causes the DNA changes that lead to Merkel cell carcinoma. Researchers have found that a common virus plays a role in causing Merkel cell carcinoma. The virus, called Merkel cell polyomavirus, lives on the skin. It doesn't cause symptoms. Experts don't know exactly how this virus causes Merkel cell carcinoma.
Risk factors
Factors that may raise the risk of Merkel cell carcinoma include:
Skin that sunburns easily. Anyone of any skin color can get Merkel cell carcinoma. But it's more common in people who have less melanin in their skin. Melanin is a substance that gives color to skin. It also helps protect the skin from damaging rays from the sun.
People with Black or brown skin have more melanin than do people with white skin. So white people are more likely to get Merkel cell carcinoma than are people with Black or brown skin.
Complications
Even with treatment, Merkel cell carcinoma often spreads to other parts of the body. When cancer spreads, healthcare professionals sometimes say it metastasizes. Merkel cell carcinoma tends to travel first to nearby lymph nodes.
Later it may spread to the brain, bones, liver or lungs. It can keep these organs from working as they should. Cancer that spreads is harder to treat and can be fatal.
Prevention
While exposure to sunlight isn't proved to cause all Merkel cell carcinomas, it is thought to be a risk factor for this cancer. Getting less sun exposure may lower your risk of skin cancer.
Try to:
For much of North America, the sun's rays are strongest between about 10 a.m. and 3 p.m. Plan to be outdoors at other times of the day, even during winter or when the sky is cloudy. When outside, stay in the shade as much as possible.
Use a broad-spectrum sunscreen with an SPF of at least 30, even on cloudy days. Apply sunscreen generously. Reapply every two hours, or more often if you're swimming or sweating.
To protect your skin from the sun, wear dark, tightly woven clothes that cover the arms and legs. Wear a wide-brimmed hat that shades the face and ears.
Don't forget sunglasses. Look for sunglasses that block both types of ultraviolet light, also called UV light, that comes from the sun. The two types are UVA and UVB.
Look at your skin often for new growths or changes in moles, freckles, bumps and birthmarks. Use mirrors to check your face, neck, ears and scalp. Report any changes to your healthcare professional.
Even though Merkel cell carcinoma most often is on the face, head and neck, look at other areas of your body. Look at your chest and trunk and the tops and undersides of your arms and hands. Look at the front and back of your legs and your feet. Look at the bottom of the feet and the spaces between your toes. Also check your genital area and between your buttocks.
Diagnosis
Merkel cell carcinoma diagnosis often starts with an exam. A healthcare professional may look at your skin and remove a sample of cells for testing. This skin cancer may be hard to diagnose because it may look like other skin growths.
During a physical exam, a healthcare professional looks at your skin for moles, freckles and other growths.
A biopsy is a procedure to remove a sample of tissue for testing in a lab. For Merkel cell carcinoma, a healthcare professional may use a tool to cut away some of the concerning skin. Other ways to do a skin biopsy involve using a shaving tool or a circular cutting tool to get some of the skin. The sample is tested in a lab to see if it is cancer.
Your healthcare professional may use other tests to find out whether the cancer has spread beyond your skin. These other tests may include:
Sentinel node biopsy. A sentinel node biopsy is a procedure to see whether cancer has spread to the lymph nodes. This procedure involves putting a dye into the skin near the cancer. The dye then flows through the lymphatic system to the lymph nodes.
The first lymph nodes that get the dye are called the sentinel nodes. A healthcare professional removes these lymph nodes and looks for cancer cells under a microscope.
Treatment
Treatment for Merkel cell carcinoma most often involves surgery to remove the cancer. If the cancer has spread beyond the skin, treatment may involve medicines or radiation.
A surgeon removes the cancer along with a border of skin that doesn't have cancer. For cancer that has spread to lymph nodes near the skin cancer, the surgeon removes those lymph nodes. This is called a lymph node dissection.
Surgery most often involves a scalpel to cut away the cancer. Sometimes, a surgeon may use a procedure called Mohs surgery.
Mohs surgery involves cutting away thin layers of skin. The surgeon uses a microscope to look at each layer for cancer. The process keeps going until there's no more cancer. The goal of Mohs surgery is to remove all the cancer without harming the healthy skin around it.
Radiation therapy treats cancer with powerful energy beams. For Merkel cell carcinoma, a healthcare professional may use radiation therapy after surgery to destroy cancer cells that remain. Radiation may be the only treatment for people who don't want to have surgery. Radiation also can treat cancer that has spread.
Immunotherapy for cancer is a treatment with medicine that helps the body's immune system kill cancer cells. The immune system fights off diseases by attacking germs and other cells that shouldn't be in the body. Cancer cells survive by hiding from the immune system. Immunotherapy helps the immune system cells find and kill the cancer cells.
Most often, immunotherapy treats Merkel cell carcinoma that comes back after treatment or spreads to other areas of the body.
Chemotherapy treats cancer with strong medicines. Healthcare professionals don't often use chemotherapy to treat Merkel cell carcinoma. But your healthcare team may suggest it if your Merkel cell carcinoma spreads to your lymph nodes or other organs, or if it returns after treatment.
Preparing for an appointment
If you have a mole, freckle or bump on your skin that concerns you, start by making an appointment with a healthcare professional. For skin cancer, you'll likely be sent to a skin specialist, called a dermatologist.
Here's some information to help you get ready for your appointment.
Ask a family member or friend to go with you to help you remember the information you get.
For Merkel cell carcinoma, questions might include:
Be sure to ask all the questions you have.
Your healthcare team is likely to ask you questions, such as:
Updated on Jan 10, 2025
© 2023 Mayo Foundation for Medical Education and Research. All rights reserved. Terms of Use