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Merkel Cell Carcinoma: What to Know

Medically Reviewed by Brunilda Nazario, MD on November 03, 2022

Merkel cell carcinoma, also known as neuroendocrine carcinoma of the skin, is a rare but aggressive type of skin cancer. It usually looks like a raised red or pinkish sore and can show up on your face, head, or neck. But it can also appear on other parts of your body.

The cancerous bump tends to grow fast in size and can quickly spread to other parts of your body. While experts aren't sure what exactly causes it, you're more likely to get it if you've had long-term sun exposure, are over 50 years old, or if your immune system is weak. Around 3,000 people are diagnosed with this cancer each year, but that number is increasing. 

Here's a look at what causes Merkel cell carcinoma, its symptoms, how to treat it, and things you can do to prevent it. 

 

What Are the Symptoms of Merkel Cell Carcinoma?

Merkel cell carcinoma can grow in size and spread to other parts of your body quickly. The key to fighting this type of skin cancer is to spot it early and treat it. 

Symptoms include:

  • A raised or dome-shaped sore that looks red, pink, or purple.
  • The bump grows quickly, usually within a few weeks or months. 
  • The bumpy sore might be firm and painless to touch.
  • The sore shows up on your face, head, or neck – the most sun-exposed parts of the body.
  • The sore appears after you’re 50 years of age or older. 

While this type of skin cancer is more common among older fair-skinned people, people of color and young people also get it. But it’s very rare and the symptoms might look slightly different.

Among Black people, skin cancer tends to show up on the legs. Due to darker skin tone, the sore-like tumor may not look like the typical red or pink bump usually seen among fair-skinned people. In one rare case, a 58-year-old Black woman had the skin cancer show up as a 2 centimeter-wide painless bump on her right elbow.  

Among younger people, the skin tumor may show up on your torso like your chest or belly.  

Because Merkel cell carcinoma is often painless and looks harmless, you might mistake it for:

  • A bug bite
  • Sore
  • Cyst
  • Stye (a painful lump by your eyelid)
  • Pimple

What Causes Merkel Cell Carcinoma?

Experts aren’t sure what exactly causes Merkel cell carcinoma. But what they do know is that this type of skin tumor begins in the Merkel cells and causes them to grow out of control. 

Merkel cells are found at the bottom of the outmost layer of skin called the epidermis. They’re connected to nerve endings in the skin that cause the sense of touch.

Researchers have also found that some Merkel cell carcinoma is linked with a common virus known as Merkel cell polyomavirus. It usually lives on the skin and doesn’t cause any symptoms. But experts don’t yet understand how this commonly found virus triggers this rare cancer within Merkel cells. Yet people who have a tumor that is negative for polyomavirus tend to have worse outcomes of survival and increased recurrence of the tumor.

Experts believe risk factors like older age and sun exposure might be the cause. But there needs to be more research done on the link between the virus and the rare tumor. 

Who's at Risk?

Risk factors can include:

Long-term sun exposure. The ultraviolet rays from the sun and those that you can become exposed to inside a tanning bed can increase your odds for this type of skin tumor.

A weak immune system. If you have HIV, use drugs that suppresses your immune system, or have certain cancers like chronic leukemia, you’re more likely to get Merkel cell carcinoma. 

Have a history of skin cancer. If you’ve had any other types of cancer, like basal cell or squamous cell carcinoma, you’re more likely to develop Merkel cell carcinoma. 

Older age. Research shows you’re more likely to get Merkel cell carcinoma if you’re 50 years old or older. In fact, 9 in 10 people  who get this rare cancer are over 50. Most people who develop it are in their 70s and 80s. 

Lighter skin tone. Fair-skinned people have higher odds of developing this rare cancer compared to people who have darker skin tones. 

How Is Merkel Cell Carcinoma Diagnosed?

If you think you have an abnormal looking sore, talk to your doctor about it. Your primary care doctor may refer you to a dermatologist -- a doctor who specializes in the skin. 

A doctor or nurse may do the following tests and exams:

Physical exam. This will include a full-body skin exam. They will look for bumps and changes in color, size, shape, or texture.

Medical history. They will take a detailed history of your health, past illnesses, and any current or previous medication use.

Skin biopsy. If you have an abnormal-looking sore or cyst, they will take a sample of it to check under a microscope. 

If they diagnose you with Merkel cell carcinoma, they may do further tests to see if cancer has spread (metastasized) to other parts of your body. This can include:

  • CT scan
  • PET scan
  • Lymph node biopsy

How Do You Treat Merkel Cell Carcinoma?

Treatment will depend on how much and where your cancer has spread. There are a few ways you can treat Merkel cell carcinoma. 

Surgery. This can include procedures to remove cancerous cells or affected body parts. 

Radiation therapy. This treatment uses high-energy X-rays and other types of radiation to kill cancer cells. 

Chemotherapy. You’ll take drugs either by mouth or injected into a vein to kill cancer cells and limit the spread.

Immunotherapy. You’ll take drugs to boost your immune system to fight off or limit the cancer's spread.

Can You Prevent Merkel Cell Carcinoma?

Sun exposure is the biggest risk factor for Merkel cell carcinoma. While there’s no specific way to prevent this rare skin cancer, you can lower your risk. 

You can:

  • Avoid the harsh sun during peak hours. Typically, this is between 10 a.m. to 4 p.m. 
  • Protect your eyes and skin on your face, neck, and head from the sun. Use a wide-brimmed hat and sunglasses to limit your exposure to UV rays.
  • Wear sunscreen regularly. Use broad-spectrum sunscreen with at least SPF 30. Wear it even on cloudy days. If you’re swimming or sweating, reapply it every 2 hours.

Keep an eye out for skin changes. If you have a mole or notice a red bump, check to see if it changes in size, color, shape, or texture. While most changes are not cancerous, it’s best to have it checked out by a doctor as soon as possible.

Show Sources

SOURCES:

Mayo Clinic: "Merkel Cell Carcinoma."

American Academy of Dermatology Association: "Skin Cancer Types: Merkel Cell Carcinoma Signs and Symptoms."

Journal of Medical Case Reports: "Merkel cell carcinoma occurring in a black woman: a case report."

National Cancer Institute: "Merkel Cell Carcinoma Treatment (PDQ) -- Patient Version."

Skin Cancer Foundation: "Merkel Cell Carcinoma Overview."

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