Merkel Cell Carcinoma

What is Merkel cell carcinoma?

Merkel cell carcinoma (MCC) is a rare skin cancer. It is also an aggressive skin cancer. MCC is considered aggressive because it can:

• Grow quickly and spread.
• Return after treatment.

Because MCC is aggressive, doctors recommend prompt treatment. The sooner this skin cancer is treated the better the outcome.

Cases of Merkel cell carcinoma have tripled in the past 20 years.

To improve a patient’s outcome, a team of doctors usually creates the treatment plan for MCC. This approach allows the patient to benefit from the expertise of specialists in different areas of medicine. The team often includes a dermatologist, a medical oncologist (cancer specialist), and a radiation oncologist (specialist in treating cancer with radiation.) Other doctors may also be a part of this team. 

It is important for patients diagnosed with MCC to:

• Keep all appointments with their doctors.
• Check their skin and lymph nodes for signs of cancer as recommended.

These actions help find cancer as early as possible.

To get a better understanding of what to look for on the skin, some patients find it helpful to look at pictures of MCC. You’ll find more pictures of this skin cancer at The American Academy of Dermatology’s page on Merkel cell carcinoma: Signs and symptoms.

Merkel cell carcinoma: Signs and symptoms

This rare skin cancer often looks harmless. Many people mistake it for a pimple, bug bite, or cyst. If you see a lump or hardened patch on your skin that looks like any pictures on this page, you should immediately make an appointment to see a dermatologist.

This appointment is especially important if you have:

• Fair skin and are 50 years of age or older.
• A disease that weakens your immune system, such as HIV or chronic lymphocytic leukemia (a cancer of the blood and bone marrow).
• Received an organ transplant.
• Had Merkel cell carcinoma (MCC) or another skin cancer.

Merkel cell carcinoma: What it looks like

MCC often appears on skin that has had lots of sun exposure. The MCC tumor tends to:

• Feel firm.
• Grow quickly (in a few weeks or months).
• Have one color, either red, pink, blue, or violet.

Merkel cell carcinoma: Symptoms

People diagnosed with MCC often say that the lump or patch was painless.

Merkel cell carcinoma: Where it appears on the body

This rare skin cancer can develop anywhere on the skin. Most MCCs, however, appear on skin that has received lots of sun exposure. About half of MCCs develop on the head or neck, with many of these forming on the eyelid. Other places that MCC tends to develop are the legs, arms, feet, buttocks, and genitals.

One of the greatest risk factors for MCC is age. Most MCCs develop in people who are 50 years of age or older. 

Merkel cell carcinoma: Who gets and causes

Who gets Merkel cell carcinoma?

Most Merkel cell cancers are diagnosed in people who are:

• 50 years of age or older (90%).
• Fair skinned and did not protect their skin from the sun (98%).

According to research studies, gender also seems to play a role. Men are twice as likely to get to MCC.

White men who are 50 years of age or older and have spent a lot of time in the sun without sun protection seem to have the greatest risk of developing MCC.

Other risk factors

Anything that increases your risk of getting a disease is a risk factor. Age, fair skin, and lots of sun exposure are the most common risk factors for MCC. Other risk factors for MCC are: 

Illness that weakens your immune system: Your immune system helps you stay healthy. Some illnesses, however, weaken your immune system. Illnesses that weaken the immune system include HIV and chronic lymphocytic leukemia (a cancer of the blood and bone marrow).

Medicine that weakens your immune system: People who received an organ transplant must take medicine for life. This medicine prevents the body from rejecting the transplanted organ. It also weakens the immune system. Other medicines can also weaken the immune system. 

If you have concerns about a medicine you take, talk with your doctor. Immediately stopping a medicine or reducing the amount of medicine you take can cause serious side effects.

Exposure to arsenic or infrared light: Being exposed to arsenic for a long time seems to increase the risk. Long-term exposure can come from drinking well water that contains arsenic. Some people are exposed to arsenic in the workplace. Infrared light is common in some workplaces and homes. Common sources of infrared light are lasers, some furnaces, and heat lamps.

PUVA therapy, using methoxsalen (meth-OX-a-len): Some patients treated with PUVA therapy receive a medicine called methoxsalen. In one study, researchers found that 3 of the 1,380 patients taking methoxsalen developed MCC. The cancer developed many years later. All of the patients had taken methoxsalen during their PUVA therapy. Two of these patients received more than 300 PUVA treatments.

What causes Merkel cell carcinoma?

Scientists are still studying what causes this skin cancer. 

A research breakthrough came in 2008 when scientists discovered a virus called the Merkel cell polyomavirus. This virus is found in many Merkel cell tumors. To gain a better understanding of this cancer, scientists are studying this virus.

If you have risk factors for Merkel cell carcinoma

Having risk factors does not mean that you will get MCC. This skin cancer is rare. You can reduce your risk by protecting your skin from the sun. This can also reduce your risk for getting other types of skin cancer.

If you are concerned that you may have MCC, you should immediately make an appointment to see a dermatologist.

Merkel cell carcinoma: Diagnosis, treatment and outcome

How is Merkel cell carcinoma diagnosed?

Diagnosis begins with an exam. Your dermatologist (or other doctor) will closely examine your skin and lymph nodes. We have lymph nodes in our neck, underarms, and other areas of the body. Lymph nodes help to protect us from illness. They often swell when we are sick.

If your doctor suspects Merkel cell carcinoma (MCC), you will need a skin biopsy. This is the only way to diagnose skin cancer. Your dermatologist can safely perform a skin biopsy during an office visit. To perform a skin biopsy, a dermatologist removes either the entire tumor or part of it. 

What your dermatologist removes will be examined under a microscope. This magnified view allows a doctor to look for cancer cells. 

Radiation treatments often play an important role in treating MCC.

How is Merkel cell carcinoma treated?

When the diagnosis is MCC, doctors with experience treating this rare skin cancer should be consulted. Each of these doctors should have expertise in a different field of medicine, such as dermatology, surgery, oncology, and radiation oncology. Working together, these doctors can create a treatment plan.

Before the doctors create a treatment plan, they want to find the stage of the cancer. Treatment differs for each stage. The stage tells doctors how deep the MCC has grown and whether the cancer has spread.

Finding the stage: To find the stage, a patient undergoes a process called staging. Staging for MCC often begins with an imaging test, such as a PET/CT scan. This allows the doctors to see if cancer has spread to organs inside the body.

After imaging tests, many patients diagnosed with MCC have a surgical procedure called a sentinel lymph node biopsy (SLNB). A SLNB can tell doctors if the cancer has spread to a patient’s lymph nodes. When MCC begins to spread, it often travels to a certain lymph node first. A SLNB can tell doctors to which lymph node the cancer would travel first and whether that lymph node or nearby lymph nodes contain cancer cells.

What happens during a SLNB

For many patients, a SLNB is an outpatient procedure. In some cases, getting a SLNB requires a short hospital stay. During this surgery, the following happens:

• The surgeon injects a dye, radioactive substance, or both into the patient. The injection is made near the MCC tumor.
• The surgeon uses a special device to follow the injected substance, which travels to the sentinel node (first node to which the cancer is likely to spread).
• The surgeon makes a small incision and removes the sentinel lymph node, and in some cases, other lymph nodes.
• A specially trained doctor, a pathologist, checks the removed lymph node(s) for cancer.
• If the pathologist finds cancer, the surgeon may remove more lymph nodes. Sometimes, the surgeon can do this during the same surgery. Sometimes, the patient needs a second surgery.

After finding and removing the lymph node(s), the surgeon may remove the Merkel cell tumor. Sometimes, removing the tumor requires another surgery.

Some patients need more imaging tests to help the doctors determine the stage of the cancer. A patient may need a CT scan, MRI, or CT/PET scan.

The stage of the cancer is determined by where it appears. The following summarizes the stages:

• Local: Skin only.
• Nodal: Skin and lymph nodes.
• Metastatic: Cancer has spread beyond the skin and lymph nodes to other areas of the body.

Patients often have questions about what their stage means. You will find a table that shows the different stages for MCC at What are Merkel cell carcinoma “stages”?

The patient’s stage plays an important role in the treatment plan. The doctors also consider the patient’s age, overall health, and personal preferences. A treatment plan for MCC will consist of one or more of these treatments:

• Surgery to remove the tumor.
• Surgery to remove lymph nodes.
• Radiation treatments.
• Chemotherapy.
• Clinical trial.

Excision (surgery): During this surgery, the surgeon removes the tumor and some surrounding tissue that looks healthy. Removing healthy looking tissue helps to catch cancer that may have traveled to an area that still looks healthy. An area can look healthy if it contains just a few cancer cells.

Mohs surgery: Because MCC often develops on the face and other areas with little fat, Mohs (pronounced “Moes”) surgery may be recommended. This specialized surgery is used only to treat skin cancer. This surgery allows the Mohs surgeon to remove less healthy looking tissue.

During Mohs surgery, the Mohs surgeon cuts out the tumor plus a very small amount of healthy looking tissue surrounding the tumor. While the patient waits, the Mohs surgeon uses a microscope to look at what was removed. The surgeon is looking for cancer cells.

If the Mohs surgeon finds cancer cells in the healthy looking tissue, the surgeon will remove another small amount of healthy looking tissue and look at it under the microscope. This process continues until the surgeon no longer sees cancer cells.

MCC can grow deep, so some patients need reconstructive surgery. This surgery is usually performed immediately after the cancer surgery.

Lymphadenectomy: This is surgery to remove lymph nodes. This surgery is also called lymph node dissection.

Radiation treatments: This is often part of the treatment plan for MCC because this cancer has a high risk of returning after surgery. Studies show that radiation treatments reduce the risk of MCC returning. Patients usually begin radiation treatments within 4 weeks of having surgery to remove the cancer.

Radiation treatments also are given to patients who cannot undergo surgery. Findings from a study suggest that radiation alone can be an effective treatment.

Some patients receive radiation treatments to help them feel more comfortable. Your doctor may refer to this as palliative therapy. This therapy does not treat the disease. It helps people feel better.

Most patients receive radiation treatments in a hospital or outpatient facility. The treatments are usually given 5 days a week, Monday through Friday, for 5 weeks. 

Chemotherapy: Doctors recommend chemotherapy for some patients who have MCC that has spread beyond the skin and lymph nodes. Chemotherapy treats the cancer with drugs that can kill the cancer cells.

Clinical trial: Some patients are encouraged to join a clinical trial. A clinical trial is a type of research study. This study tests how well new a treatment or a new way of treating a disease works. For some patients joining a clinical trial may be the best treatment option.

What is the outcome for patients with MCC?

MCC is an aggressive cancer. It can return after treatment. It often returns within the first 6 to 12 months after diagnosis. For this reason, it is essential to keep all follow-up appointments with your doctors.

On a positive note, findings from a research study show that patients who do not have cancer in their lymph nodes have an excellent prognosis (outcome). Patients who have stage I, II, or III MCC tend to do better than patients who have MCC that has spread beyond the lymph nodes.

Merkel cell carcinoma: Tips for managing

Findings from research studies suggest that patients treated for Merkel cell carcinoma (MCC) should:

1.    Keep all follow-up appointments with your doctors. MCC is an aggressive skin cancer. It can return after treatment. For this reason, doctors who have expertise in treating MCC recommend: 

• Every patient treated for MCC needs a follow-up visit every 3 to 6 months for the first 2 years.
• After 2 years of cancer-free exams, the patient should return every 6 to 12 months for a complete exam.
• Each exam should include a complete skin exam and an exam of certain lymph nodes.

These follow-up visits help find skin cancer in the earliest stage. The sooner the cancer is found and treated, the better the outcome.

2.    Perform skin self-exams as often as your dermatologist recommends. If you have received treatment for MCC, it is essential that you learn how to perform a skin self-exam. Your dermatologist or someone in your dermatologist’s office can teach you exactly what you need to know, including how to examine certain lymph nodes. 

Contact your dermatologist immediately if you find any new growth or rough patch on your skin; or feel a change in your lymph nodes.

3.    Protect your skin from the sun. If you have had MCC, you must always protect your skin from the sun. The sun’s rays damage skin. Your dermatologist can offer you specific tips that meet your needs. 

4.    Ask your doctors what else you can do to improve your outcome. Some doctors recommend eating a healthy diet and exercising to keep the immune system strong. Getting enough sleep also is important. Be sure to ask your doctors what could help you.