Merkel Cell Carcinoma

Merkel Cell Carcinoma

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What is Merkel cell carcinoma?

Merkel cell carcinoma (MCC) is a rare skin cancer that is aggressive (grows very fast). It starts in Merkel cells, which are cells in the skin’s top layer. MCC can spread quickly to other parts of the body. It’s hard to treat once it spreads.

MCC can be serious. If it’s not treated, it can quickly spread to lymph nodes, bones, the liver, and lungs.

Merkel cell carcinoma is also called neuroendocrine carcinoma of the skin. It’s a type of neuroendocrine cancer. Neuroendocrine (NOOR-oh-EN-doh-krin) cells are like both nerve cells and the cells that make hormones (endocrine system cells).

What does Merkel cell carcinoma look like?

Merkel cell carcinoma can be located on areas of your skin exposed to the sun. That includes your face, neck, arms, and legs.

MCC can look like a small, firm, and painless bump or nodule (a growth or lump) on your skin. It can be red or scaly. It may have ulceration, which means there’s broken skin covering the bump.

The shape of the bump or nodule can be round, or with sides that are not equal. Sometimes, the tumor can look like a pimple, wart, or cyst. This makes it hard to tell MCC from other skin conditions.

Merkel cell carcinoma can look different in everyone. The only way to diagnose it is through a biopsy. This is a procedure to remove a small sample of tissue or cells to examine under a microscope.

Where does Merkel cell carcinoma often form?

MCC can form in any area of the skin. It’s most common on areas of skin exposed to the sun. That includes your face, neck, arms, and legs.

No one knows the exact cause of MCC. It could be caused by exposure to ultraviolet (UV) light from the sun and other sources. It also could be related to having a weakened immune system.

Symptoms of Merkel cell carcinoma

The symptoms of MCC depend on the tumor’s size and location. Common symptoms include:

  • A painless, firm bump or nodule on the skin that grows fast.
  • A red, scaly, or ulcerated area on the skin.
  • A new mole that changes in size, color, or shape

Less common symptoms can include:

  • A swollen lymph node near the site of the tumor.
  • Fatigue (feeling very tired).
  • Loss of appetite.
  • Weight loss you can’t explain.

Advanced MCC can cause more severe symptoms. They include:

  • Pain in the area that has cancer.
  • Numbness or tingling in the area that has cancer.
  • Limb paralysis (puh-RA-lih-sis), which means you can’t move the limb that has cancer.
  • Bone fractures (breaks) caused by weakened bones. It’s important to talk with your healthcare provider if you’re worried about a new or changing skin lesion. Treatment is more successful if Merkel cell carcinoma is found early, and treatment starts right away.

Merkel Cell Carcinoma Risk Factors

These are the risk factors for Merkel cell carcinoma, an uncommon skin cancer:

  • Sun exposure.
  • Fair skin.
  • A weakened immune system
  • Age

It is very unusual for family members related by blood to get Merkel cell carcinoma.

Sun Exposure

Overexposure to ultraviolet (UV) radiation from the sun is the major risk factor for skin cancer. Some Merkel cell carcinomas are caused by sun exposure, especially in sun-exposed areas like the head and neck. The radiation reaches you by invisible rays from the sun. The 2 kinds of UV radiation are UVB and UVA.

UVB radiation causes sunburns and blistering. Scientists think UVB causes most skin cancers. Merkel cell carcinoma most often starts in people who were exposed to UVB radiation, especially if they had sunburns or blistering. People who work outside, spend time at the beach, or do outdoor sports have a higher risk for skin cancer.

UVA radiation also causes skin damage. UVA rays can travel through glass and clouds. Exposure to UVA rays can lead to early aging and skin cancer, according to the National Cancer Institute. Sun lamps and tanning beds also cause exposure to harmful UVA rays. You should avoid them.

Fair Skin

You’re at higher risk of getting skin cancer, including Merkel cell carcinoma, if you have any of these:

  • Fair skin.
  • Blue or light-colored eyes.
  • Blond or red hair.

People with fair skin have less melanin, a skin pigment. Melanin gives skin, hair, and eyes their color. It also gives some natural protection from the sun. People with dark skin can get Merkel cell carcinoma, but this is very rare. Skin that freckles or sunburns easily can be a warning sign you’re at risk for Merkel cell carcinoma.

Weakened Immune System

People with a weakened immune system are at higher risk for basal cell carcinoma. This includes people who have HIV, lymphoma, or leukemia. It also includes people who are getting chemotherapy, or drugs to prevent organ transplant rejection.


Merkel cell carcinoma is more common as you get older. More than half of people with this cancer are diagnosed after age 70.

Skin Cancer Prevention

The best way to protect yourself from skin cancer is to avoid ultraviolet (UV) light from the sun’s rays. We recommend you:

  • Wear protective clothing such as long-sleeve shirts, wide-brimmed hats, and sunglasses.
  • Protect yourself from sun rays by wearing broad-spectrum sunscreen. Broad spectrum means it blocks both types of UV rays (UVA and UVB). 
  • Apply sunscreen with an SPF of 30 or higher 30 minutes before going outside. Do this even on cloudy days and in the winter.
  • Apply a thick layer of sunscreen, about 2 tablespoons, on your face and body.
  • Reapply sunscreen every 2 hours and after swimming, toweling, or sweating.
  • Stay out of the sun from 10 a.m. to 4 p.m. when rays are the strongest.
  • Get into the shade whenever possible.
  • Do not use indoor tanning machines.

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