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Merkel Cell Carcinoma

What Is Merkel Cell Carcinoma?

Merkel cell carcinoma, also known as neuroendocrine carcinoma of the skin and trabecular cancer, is a rare type of skin cancer. It gets its name from Merkel cells, the cells located in the outermost layer of our skin.

Scientists are still trying to understand what causes Merkel cell carcinoma. The three main contributing factors include:

  • Sunlight exposure
  • A weakened immune system
  • Infection from a specific virus named Merkel cell polyomavirus

Merkel cell polyomavirus causes about eight in 10 cases of Merkel cell carcinoma. This virus is very common but does not cause disease in most people. Researchers believe it occurs when the immune system becomes weakened from age, other medical conditions, or certain medications.

The other two out of 10 cases result from long-term skin damage from ultraviolet (UV) light from the sun.

The biggest risk factor for Merkel cell carcinoma is increasing age. Men are more likely to get this cancer than women.

Since UV light exposure is a risk factor, light-skinned people have a higher risk of getting this cancer than people with darker skin. People with light hair and eyes who burn or freckle easily are at the highest risk.

Where you live and how much time you spend outside both impact your chances of getting Merkel cell carcinoma. For example, rates are higher in Hawaii than in any other U.S. state.

Merkel cell carcinoma is very aggressive. If it is not recognized, diagnosed, and treated, it can metastasize, or spread, to other parts of the body. The disease first impacts the lymph nodes, then spreads to the bones, liver, lungs, and brain.

The best way to protect yourself from Merkel cell carcinoma is to protect your skin from UV light. Using sunscreen with an SPF of 30 or more, clothing, hats, and shade to protect your skin lowers your risk of developing Merkel cell carcinoma. You should also avoid tanning beds and sunlamps.

The first sign of Merkel cell carcinoma is usually a small painless bump on the skin that gets exposure to the sun, such as the head, neck, arms, or legs. It might look like a bug bite, a sore, a stye, a cyst, or a pimple. Sometimes it is tender, sore, or itchy, but often it is painless.

This small bump may be skin-colored, pinkish, or reddish-purple. It might be shiny or have small widened blood vessels visible. The lump tends to grow very quickly, but the person often does not have other symptoms.

The first step in a diagnosis is a physical and skin exam. The doctor will feel the lymph nodes closest to the bump to see if they're enlarged. The doctor will also examine the skin on the rest of your body to see if there are other spots or lumps.

If your family doctor suspects it could be cancer, they will refer you to a dermatologist. The dermatologist may use a special magnifying glass with a light to look more closely at your skin. They may also take a biopsy, a sample of your skin, to examine under a microscope.

Some biopsies can leave a scar. If that bothers you, ask your doctor about possible scarring before the procedure.

This cancer can look similar to many other conditions, so your doctor will need to rule out other possibilities. Some conditions they must rule out are other cancers, while others are benign, or harmless, conditions.

Your doctor may also recommend imaging scans such as an MRI, CT, or PET scan to see if any cancer has spread to other body parts.

UPMC Hillman Cancer Center offers a complete continuum of care through the combined expertise of our health care teams. The team will look at the results of your skin biopsy to better understand the specific characteristics of cancer. Then they will design a personalized treatment plan.

The size, location, depth, and involvement of other tissues are all factors that help our experts decide the best course of treatment. UPMC Hillman Cancer Center also offers the chance to take part in clinical trials of breakthrough skin cancer treatments.

There are four main types of treatments for Merkel cell carcinoma:

  • Surgery
  • Radiation
  • Immunotherapy
  • Chemotherapy

Surgical treatments for Merkel cell carcinoma

The first step in treating Merkel cell carcinoma is usually surgery to remove the tumor, assuming it has not spread beyond your lymph nodes. Your surgeon will remove the tumor and surrounding tissue and may perform a sentinel lymph node evaluation to assess if the cancer has spread to the lymph nodes. This can allow for accurate staging, which will then guide consideration for preventative treatments or inclusion into clinical trials.

Surgery usually leaves some type of scarring. The most common risk for surgeries is infection. Ask your doctor how to reduce your risk of infection after surgery and about any other possible side effects.

Radiation treatments for Merkel cell carcinoma

Some patients may undergo radiation a few weeks after surgery to lower the risk of the cancer returning. The radiation destroys any cancerous cells left behind after surgery.

If you have stage IV Merkel cell carcinoma or cannot have surgery, radiation or immunotherapy may be the first treatment step.

Common side effects of radiation include skin irritation, changes in skin color or texture, hair loss, and fatigue.

Immunotherapy treatments for Merkel cell carcinoma

If the cancer has spread, your doctor may recommend immunotherapy. Clinical trials suggest immunotherapy drugs may be more effective against Merkel cell carcinoma than chemotherapy.

Two FDA-approved immunotherapy drugs for Merkel cell carcinoma are avelumab and pembrolizumab. Side effects of immunotherapy drugs can include fatigue, inflammation, itchiness, skin reactions, high or low blood pressure, and flu-like symptoms.

Chemotherapy treatments for Merkel cell carcinoma

Chemotherapy refers to drugs that kill quickly dividing cells, including cancer cells.

However, adjuvant chemotherapy is not recommended in all patients.

Research so far has not shown a strong benefit from adjuvant chemotherapy for patients with Merkel cell carcinoma. Chemotherapy is generally recommended primarily for patients who have not responded to radiation and cannot receive immunotherapy.

Side effects include hair loss, fatigue, nausea, and vomiting. The drugs can sometimes cause patients' health to deteriorate more.

Doctors at UPMC Hillman Cancer Center believe the best skin cancer treatment begins with a focus on you. As the only NCI-designated Comprehensive Cancer Center in the region, we offer the latest cancer treatments and research, and a range of services to support you and your loved ones. These services include mental health care, nutrition planning, pain management, interpreter services, and palliative care.

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