What is Merkel cell cancer (MCC)?
MCC is a rare, highly aggressive, and dangerous form of skin cancer. It starts when cells in the skin called Merkel cells start to grow out of control. Merkel cells are found in the top layer of the skin (called the epidermis). These cells are close to our nerve endings and help us sense light touch. Merkel cells can grow quickly and can spread to other parts of the body when the cancer is still at an early stage.
MCC is most likely to be cured when it is found early. However, because MCC is an aggressive cancer, delays in detection can lead to a late diagnosis which makes treating it very difficult. In addition, it commonly comes back after treatment.
Though it is estimated that there are about 1600 cases of MCC each year in the United States, the incidence of the disease has more than tripled over the past 20 years. This is likely due to a combination of increased detection and more people having risk factors for MCC.
The exact cause of MCC is not known, though it appears that there is a strong link between MCC and the body’s immune system. For example, people who have had organ transplants, who are infected with HIV, or who have chronic lymphocytic leukemia, are at greater risk for developing MCC. This may be because patients with a weakened immune system are more likely to become infected by a virus called Merkel cell polyomavirus. In fact, about 80% of MCC lesions contain this virus.
What are the risk factors for MCC?
In addition to infection with the Merkel cell polyomavirus in people with weakened immune systems, risk factors that have been associated with MCC include:
- Exposure to a lot of natural sunlight
- Exposure to artificial sunlight (for example, tanning beds or UV light from psoriasis treatment)
- Being over 50 years of age
- Having lighter skin (Caucasian)
- Being male
- Having a history of other types of cancer
What are the signs and symptoms of MCC?
MCC usually appears as a single, painless bump on the skin. These bumps are called lesions. The most common site for MCC to occur is the head and neck, followed by the arms and legs. The lesion is typically red/pink, although blue/purple is also common. MCC lesions vary in size but when the cancer is found, they are on average about 17 mm (about the size of a dime).
Using AEIOU to identify MCC
Researchers have used the first letter of the 5 most common signs and symptoms of MCC to come up with the acronym AEIOU to help healthcare providers identify the disease. Knowing these features can also help you talk with your healthcare provider about any lesions you notice on your skin.
- A (Asymptomatic—the lesion isn’t tender or sore)
- E (Expanding rapidly—the lesion is getting bigger quickly)
- I (Immune suppression/weakened immune system)
- O (Older than age 50)
- U (UV- or sun-exposed area. The lesion is on an area of your body that gets a lot of sun or UV light)
Diagnosing and treating MCC
One of the issues faced by healthcare providers is that an MCC lesion may look like a cyst or swelling from an inflamed hair follicle. In a clinical study, 56% of Merkel cell carcinomas were initially thought to be benign (non-cancerous) by physicians. If you notice any new or changing lesions on your skin—no matter how minor—talk with your healthcare provider. It is important not to delay time to detection.
If your healthcare provider suspects that a lesion on your skin may be MCC, he or she will likely take a careful medical history and perform a physical exam. If your healthcare provider thinks you may have MCC, he or she will do a skin biopsy. That means removing the lesion and sending it to a lab where it will be viewed under a microscope to examine and confirm whether there are any cancerous cells.
Treatment of MCC is based on the stage of the disease (how far it has spread) and the overall health of the patient. The main treatments are surgery (to remove the lesion), radiation, and chemotherapy and other systemic therapies (medicines that spread throughout the body to treat cancer cells).
Research is underway to better understand this disease and to discover treatments. For more information about available clinical trials for Merkel cell carcinoma, go to clinicaltrials.gov or Pfizer: Find a Trial.
Learn more about sun safety
Exposure to the sun is one risk factor for MCC that we can control. We all need some sun exposure, and it’s important to engage in some physical activity outdoors, but too much sun can be harmful. Find out what you can do to stay healthy in the sun.
Kanwarjit (KJ) Singh, MD, was the US Medical Affairs Team Leader of Immuno-Oncology and Renal Cell Cancer during his employment at Pfizer.
Maria Nduati, PharmD, is a pharmacist and Pharmacy Fellow in Medical Affairs at Pfizer.