Merkel Cell Carcinoma Symptoms and Signs

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Merkel cell carcinoma (MCC) usually appears as a fast growing, firm, painless lump on areas of the skin that have had a lot of sun exposure.

It’s important to recognize the signs and symptoms because the earlier the disease can be detected, the more effective the treatment will likely be.

Take Charge of Your Health

Talk to your primary care provider if you have symptoms that you think may be Merkel Cell Carcinoma. UW Medicine Primary Care can help you get started with screening. Learn about Fred Hutch's relationship with UW Medicine.

Most Common Merkel Cell Carcinoma Symptoms

  • Firm, painless nodule: MCC nodules (bumps) often look shiny and can be red, purple or blueish-red. They usually are not tender when touched.
  • Rapid growth: The bumps may grow quickly, and sometimes you can notice growth happening over just a few months or even weeks.
  • Location of nodules: Common areas of the body where MCC appears include the head, neck, arms and legs.

Merkel Cell Carcinoma Risk Factors

  • Age: People over the age of 50 are at a higher risk for MCC
  • Sun exposure: Prolonged exposure to ultraviolet (UV) light from the sun or tanning beds increases the risk of developing MCC
  • Weakened immune system: People who have conditions that suppress (weaken) their immune system, such as HIV/AIDS, can be at a higher risk for developing MCC. Also, people who have had organ transplants or take certain medications that suppress the immune system can also be at higher risk.

When a Nodule Should Be Examined

If you notice a new, rapidly growing, painless lump on your skin — especially in areas where you have had a lot of sun exposure — you should see your primary care provider as soon as possible. The earlier your condition is diagnosed, the easier it will be to treat.

Paris Malachias and family
Paris Malachias, center, and his family visiting Malachias' village church in 2024 on the Greek island of Chios. Courtesy of the Malachias family

A Rare Skin Cancer Diagnosis Requires a Balancing Act Between Suppressing and Boosting the Immune System

As a kidney transplant recipient, Paris Malachias was accustomed to dealing with skin cancer. It’s a common side effect of post-transplant immunosuppressants, which leave transplant recipients extra sensitive to sun, and Malachias had developed multiple basal cell carcinomas over the years. But in the fall of 2022, he noticed a pimple on his face that didn’t look like the lesions he’d had removed.

When it didn’t go away, a dermatologist biopsied it. The results came back with Merkel cell carcinoma.

Read Paris' Story

Merkel Cell Carcinoma Symptoms FAQ

While a painless, rapidly growing bump can be a sign of MCC, it could also be a sign of another type of skin cancer — or it could be a growth that is noncancerous. The only way to know for certain is to see a provider so they can examine your skin firsthand and, if needed, perform a biopsy. A biopsy involves taking a small sample of tissue from the affected area and sending it to a lab to be tested.

Yes. There is an acronym you can use to help determine if a growth is Merkel cell carcinoma. It is "AEIOU" and helps identify the key warning signs of MCC:

  • A: Asymptomatic lesion (not painful or tender)
  • E: Expanding rapidly
  • I: Immunosuppressed (this means you have a weakened immune system)
  • O: Older than 50
  • U: UV-exposed skin

Yes. While MCC develops on sun-exposed areas most often, it can also occur on parts of the body that receive little sun exposure. As always, if you have a new growth or concern about a skin lump that is changing, you should make an appointment with your primary care provider for an exam.