Merkel Cell Carcinoma
Merkel cell carcinoma is a rare and aggressive type of cancer that forms in the outer layer of the skin.
The disease is named after Merkel cells, which are located close to nerve endings in the skin. Merkel cells play a role in the sense of touch.
Doctors once thought Merkel cell carcinoma developed from these cells. While researchers are still studying the disease, they now believe it forms from other types of cells. As these cells mutate and become cancerous, they begin to look and behave like Merkel cells.
The disease is sensitive to treatments like radiation and immunotherapy, but it tends to grow and spread, or metastasize, quickly.
Merkel cell carcinoma is a type of neuroendocrine tumor. When healthy, neuroendocrine cells receive information from the nervous system and release hormones in response. While this affects prognosis and treatment for some cancers, it does not impact Merkel cell carcinoma patients.
Merkel cell carcinoma statistics
Merkel cell carcinoma is a rare cancer, affecting fewer than 1 out of 100,000 people a year. Less than 3,500 people in the United States are diagnosed with the disease each year.
While rare, Merkel cell carcinoma is aggressive. It is the second leading cause of skin cancer death, after melanoma. It can quickly grow and spread. If the disease is caught before it has spread, the five-year survival rate is 75%. If the cancer has spread to the lymph nodes, it is 64%. Merkel cell carcinoma that has spread to distant sites has a 24% survival rate.
Merkel cell carcinoma risk factors
A risk factor is anything that increases the chance of developing a particular disease. The risk factors for Merkel cell carcinoma include:
- Age: Merkel cell carcinoma cases rise with age. It is rarely diagnosed in people younger than 50.
- Gender: Men are more likely to develop Merkel cell carcinoma than women.
- Race: Merkel cell carcinoma is most often diagnosed in white people.
- Ultraviolet (UV) light exposure: UV light can come from natural sunlight or tanning beds. It damages the skin and is a leading cause of skin cancer.
- A weakened immune system: Patients with a weakened immune system have an increased risk for Merkel cell carcinoma. Causes of a weakened immune system include:
- Immunosuppressive drugs, including those taken by people who have had an organ transplant or an autoimmune disease
- HIV infection
- Cancers that impact the production of immune system cells, like leukemia and lymphoma
- Other cancer diagnoses: People who have had a previous cancer diagnosis are at an increased risk for Merkel cell carcinoma.
- Merkel cell polyomavirus: Up to 80% of Merkel cell carcinoma cases in the United States are connected to Merkel cell polyomavirus. This virus is found in most healthy people. It has no symptoms and is easily cleared by the body, but in a small number of people it may contribute to the development of Merkel cell carcinoma.
High exposure to ultraviolet rays can cause anyone to get skin cancer. But some people are more likely to develop skin cancer than others.
It’s important to understand your skin cancer risks and learn how to monitor skin changes. That way, we can catch anything suspicious early, when it’s easiest to treat.
Certain factors can increase your chances of developing skin cancer
Here are some factors that make you more likely to develop skin cancer.
1. History of blistering sunburns or frequent sun exposure. Ultraviolet light is a known carcinogen just like tobacco, so we need to be serious about protecting ourselves. Just one or two blistering sunburns as a child increases the risk of melanoma as an adult. Melanoma is the most serious form of skin cancer.
2. Light skin, eyes or hair. Anyone can get sunburned, but if you have light or fair skin, this means you have less melanin – a pigment that gives your skin its color. You also have less melanin if you have blue or green eyes or blond or red hair.
Less melanin can cause you to sunburn more easily and more often, thus increasing your risk for skin cancer.
Staying out of the sun, covering your skin and applying sunscreen with SPF 30 or higher regularly can reduce your chances of getting a sunburn, which can cause skin damage and ultimately, skin cancer.
3. Many moles or freckles. If you have many moles or freckles, it’s important to keep an eye on them. Normal freckles and moles are typically tan or brown and are round or oval-shaped. Look out for any that are getting larger, painful, bleeding, itchy or scabby, as they could be cancerous. Use the ABCDEs of skin cancer to check your skin.
4. Personal or family history of skin cancer. Does skin cancer run in your family? If a close relative has had skin cancer, you might be at greater risk as well. A dermatologist can do a full-body screening to help you know for sure.
If you have had skin cancer before, it’s more likely that you’ll get it again. Certain rare genetic disorders and other medical conditions also can increase that risk.
5. Tanning bed use. The UV rays from tanning beds cause damage to your skin, which can increase your risk of skin cancer, including melanoma. They can often emit more UV radiation than the sun and also cause premature aging.
Check your skin for changes
Everyone should check their skin for signs of cancer. But if you think you are at an increased risk for skin cancer, see a dermatologist at least once a year for a skin screening exam.
When you check your skin for cancer, look for abnormal moles, suspicious spots and anything that looks new or out of the ordinary. Use the ABCDEs to help you spot changes that could be signs of cancer:
- Asymmetry: Take note if two sides of a mole look different from one another.
- Border: Watch for moles where the border is crooked, irregular or jagged.
- Color: Look for moles that are multi-colored. This may be a sign of skin cancer.
- Diameter: Check the diameter of moles, and get any larger than 6 millimeters wide checked out. That’s about as wide as a pencil eraser.
- Evolution: See your doctor if a mole has changed in feeling, shape or size.
Make sure you look at all areas of your body – even those that aren’t exposed to the sun. Take a good look at these areas:
- All areas of the scalp. Use a comb to expose your scalp. A hand-held mirror can help you look at areas on the back of the scalp.
- Face, especially the eyelids, nose, and ears. Look inside your mouth, including your lips, tongue and inner cheeks.
- Neck, chest and abdomen. Lift all skin folds to examine the skin underneath. Raise your arms and check the underarm areas, as well as the sides of your upper body.
- Arms and hands. Look between your fingers and fingernails.
- Back and neck. Face away from the mirror and use the hand-held mirror to examine the back of your neck and back. From there, continue down your body and inspect your buttocks and the backs of your legs.
- Genitals, legs and feet. Use the hand-held mirror to check your genitals and inner thighs. Look at the front of your legs, tops and soles of your feet and the spaces between your toes and toenails.
As you do a self-exam, you’ll become familiar with your skin and know what looks normal and what seems unusual. Let your dermatologist know about any suspicious skin changes to take a closer look.
Ask a family member or friend to check your scalp, back and other areas that may be hard to see.
You can also take pictures of your moles and compare them over time. Mark your calendar or set a reminder on your smartphone to check your skin each month.
Remember, spotting skin changes early can help us catch cancer early when it’s easiest to treat.
Request an appointment at MD Anderson online or by calling 1-877-632-6789.
Merkel cell carcinoma symptoms
In general, any new or changing spots on your skin that persist for two weeks or more should be brought to your doctor’s attention.
Merkel cell carcinoma’s main symptoms include:
- A single lump that is often painless. The lump is firm and often red or violet in color. It usually appears in places that get lots of sun exposure, including the head, neck, arms and legs. In some cases, the lump may break open and bleed.
- Swollen lymph nodes near the cancer site. This is a symptom in people who have more advanced disease.
These symptoms do not always mean you have cancer. However, it is important to discuss any symptoms with your doctor since they may signal other health problems.
Merkel cell carcinoma diagnosis
Any persistent changes to the skin should be brought to your doctor's attention. Your doctor will then conduct a physical exam of the suspected area of tissue. If cancer is suspected, they will conduct further tests to get a clear diagnosis.
Merkel cell carcinoma is a rare disease. Often doctors do not suspect this cancer before it is diagnosed. Because it is rare, diagnosing Merkel cell carcinoma may take an experienced dermatopathologist, a doctor who specializes in diagnosing skin conditions. MD Anderson has a team of expert dermatologists and dermatopathologists experienced in recognizing Merkel cell carcinoma and its subtypes.
The following tests are used to diagnose Merkel cell carcinoma and to track how the patient is responding to treatment.
Biopsy
A biopsy is the only way to definitively diagnose Merkel cell carcinoma. During a biopsy, a small tissue sample is removed and examined under a microscope for cancer cells. Depending on tumor location, some biopsies can be done on an outpatient basis with only local anesthesia. Other times patients must undergo a surgical biopsy under general anesthesia.
There are several ways to biopsy a suspected Merkel cell carcinoma. They include:
Shave biopsy: A small section of the suspected cancer is shaved off the lump using a simple instrument like a scalpel or surgical scissors and studied under a microscope.
Punch biopsy: A special tool retrieves suspected cancer cells by punching a hole in the skin.
Incisional biopsy: Doctors surgically remove a portion of the suspected cancer.
Excisional biopsy: Doctors surgically remove the entire suspected cancer. They also remove a small amount of surrounding healthy tissue to ensure no cancer cells are left behind. In addition to helping diagnose skin cancers like Merkel cell carcinoma, excisional biopsies can serve as surgeries to help cure the disease.
Imaging exams
Merkel cell carcinoma patients usually undergo imaging exams after they have been diagnosed with cancer. These exams are used to look for cancer inside the body. They can help determine the cancer’s stage by locating tumors. Imaging exams can also track how the body is responding to treatment.
There are many types of imaging exams. The ones used for Merkel cell carcinoma include:
PET/CT Scan: PET/CT scans combine two types of imaging exams. Positron emission tomography (PET) scans use a small dose of radioactive sugar that is injected into a patient. A scanner shows where the body distributes the sugar, allowing for the creation of an image. This image can help radiologists find cancer cells in the body. The computed tomography (CT) scan uses an X-ray machine to take several pictures from different angles, providing a highly detailed image.
Ultrasound: Ultrasound operates with high-energy sound waves that bounce off internal tissues and organs and produce echo patterns. The echo patterns create a picture called a sonogram, which can be seen on an ultrasound machine. For Merkel cell carcinoma, ultrasound is used to image the patient’s lymph nodes.
CT Scan: A computed tomography (CT) scan uses an X-ray machine to take several pictures from different angles, providing a highly detailed image.
MRI: Magnetic Resonance Imaging, or MRI, uses magnetic fields and radio waves to generate pictures of the body’s soft tissue and organs.
Blood and urine tests
These tests can help monitor the disease and how the patient is responding to treatment.
Merkel cell carcinoma stages
If you are diagnosed with Merkel cell carcinoma, your doctor may do more tests to determine how big the tumor is and whether the cancer has spread to more places in the body.
This process is called staging, and it helps your doctor plan your treatment. It also provides information about the expected outcome, or prognosis, of your cancer.
Merkel cell carcinoma staging summary
In stage 0, some abnormal cells have developed, but they haven’t turned into cancer.
In stage I, the cancer is small and hasn’t spread into nearby tissue.
In stage II, the cancer is larger and may have spread to nearby tissue, like muscle or cartilage.
In stage III, the cancer has spread to nearby lymph nodes.
In stage IV, the cancer has spread to distant parts of the body, like the brain, liver or lungs.
Detailed stages for Merkel cell carcinoma
Source: National Cancer Institute
Stage 0 (carcinoma in situ)
In stage 0, abnormal Merkel cells are found in the top layer of skin. These abnormal cells may become cancer and spread into nearby normal tissue.
Stage I
In stage I, the tumor is two centimeters or smaller.
Stage II
Stage II Merkel cell carcinoma is divided into stages IIA and IIB.
- In stage IIA, the tumor is larger than two centimeters.
- In stage IIB, the tumor has spread to nearby connective tissue, muscle, cartilage, or bone.
Stage III
Stage III Merkel cell carcinoma is divided into stages IIIA and IIIB.
In stage IIIA, either of the following is found:
- the tumor may be any size and may have spread to nearby connective tissue, muscle, cartilage, or bone. A lymph node cannot be felt during a physical exam but cancer is found in the lymph node by sentinel lymph node biopsy or after the lymph node is removed and checked under a microscope for signs of cancer; or
- a swollen lymph node is felt during a physical exam and/or seen on an imaging test. When the lymph node is removed and checked under a microscope for signs of cancer, cancer is found in the lymph node. The place where the cancer began is not known.
In stage IIIB, the tumor may be any size and:
- may have spread to nearby connective tissue, muscle, cartilage, or bone. A swollen lymph node is felt during a physical exam and/or seen on an imaging test. When the lymph node is removed and checked under a microscope for signs of cancer, cancer is found in the lymph node;
- or cancer is in a lymph vessel between the primary tumor and lymph nodes that are near or far away. Cancer may have spread to lymph nodes.
Stage IV
In stage IV, the tumor has spread to skin that is not close to the primary tumor or to other parts of the body, such as the liver, lung, bone, or brain.
Merkel cell carcinoma treatment
Merkel cell carcinoma is a rare cancer. As a top-ranked cancer center, MD Anderson treats hundreds of Merkel cell carcinoma patients each year. This gives our surgeons, medical oncologists, radiation oncologists and dermatologists extensive experience in treating the disease.
Merkel cell carcinoma treatment plans
Patients with Merkel cell carcinoma that has not spread to the lymph nodes or beyond typically receive surgery and/or radiation therapy.
If the cancer has spread to the lymph nodes but no further, treatment may include surgery, radiation therapy and cancer drugs like immunotherapy.
For cancers that have spread beyond the lymph nodes to distant parts of the body, treatments include radiation therapy and cancer drugs. Surgery may be recommended for select patients.
Surgery
Surgery is a key treatment for most early-stage Merkel cell carcinoma patients.
A common surgical approach is wide local excision. During this procedure, the surgeon cuts out the tumor along with a small amount of surrounding healthy tissue. This helps ensure no cancer cells are left behind.
Surgery will also involve the lymph nodes. Lymph nodes help transport immune system cells and clean cellular waste from the body. Nearby lymph nodes are often the first place cancer moves when it spreads, or metastasizes.
If imaging exams and other tests before surgery show that cancer has spread to the lymph nodes, they will be removed.
If tests did not show cancer in the lymph nodes before the surgery, doctors will remove and examine the very first lymph nodes where cancer would appear. This is called a sentinel lymph node biopsy.
If these sentinel lymph nodes are clear, no further surgery is needed. If they contain cancer cells, additional surgery and treatment may be required.
Mohs surgery
During Mohs surgery, a dermatologic surgeon removes a very thin layer of cancer tissue and examines it under a microscope. If cancer cells can be seen in the layer, the doctor continues shaving off layers one at a time until no cancer cells are found.
Mohs is often used to successfully treat other types of skin cancer, but MD Anderson doctors typically do not recommend it for Merkel cell carcinoma. If surgery is needed, they usually recommend local excision, which has a better chance of removing all cancer cells of this disease.
Radiation therapy
Radiation therapy uses powerful, focused beams of energy to kill cancer cells. There are several different radiation therapy techniques. Doctors can use these to accurately target a tumor while minimizing damage to healthy tissue.
Radiation therapy is very effective against Merkel cell carcinoma, so it is included in most treatment plans. In select cases, it is the only therapy doctors recommend.
Learn more about radiation therapy.
Immune checkpoint inhibitors
Immune checkpoint inhibitors are a type of immunotherapy. They stop the immune system from turning off before cancer is completely eliminated. Patients may receive a single immunotherapy drug or multiple drugs in combination.
Learn more about immune checkpoint inhibitors.
Chemotherapy
Chemotherapy drugs kill cancer cells, control their growth or relieve disease-related symptoms. Chemotherapy may involve a single drug or a combination of two or more drugs, depending on the type of cancer and how fast it is growing. Merkel cell carcinoma is very sensitive to chemotherapy.
Why choose MD Anderson for your Merkel cell carcinoma treatment?
Choosing where to go for cancer treatment is one of the most important decisions a patient can make.
Merkel cell carcinoma is a rare cancer. Most doctors see only a handful of cases in their career.
It is not rare at MD Anderson, though. As a top ranked cancer center, we see hundreds of Merkel cell carcinoma patients each year in a clinic dedicated to caring for patients with rare skin cancers.
Thanks to the number of patients we treat, our doctors have incredible expertise when evaluating patients and designing Merkel cell carcinoma treatment plans. They work in teams consisting of a surgeon, radiation oncologist, medical oncologist and dermatologist to develop treatments tailored to each specific patient.
Thanks to this expertise, MD Anderson is also one of the few hospitals that that has clinical trials dedicated exclusively to Merkel cell carcinoma. Your treatment plan might include a trial of a new cancer drug or new combinations of existing drugs. It could also offer treatments that are less intense but just as effective at fighting cancer. Your care team will recommend a clinical trial only if they believe it is the best treatment for you.
And at MD Anderson you will also be surrounded by the strength of one of the nation's largest and most experienced cancer centers. From support groups to counseling to integrative medicine care, we have all the services needed to treat not just the disease, but the whole person.