Merkel cell carcinoma
Cancer starts when cells begin to grow out of control. Cells in nearly any part of the body can become cancer, and can then spread to other areas of the body. To learn more about how cancers start and spread.
Merkel cell carcinoma (MCC) is an uncommon type of skin cancer. It starts when cells in the skin called Merkel cells start to grow uncontrollably. This type of cancer can grow quickly and can be hard to treat if it spreads beyond the skin.
Merkel cells are thought to be a type of skin neuroendocrine cell, because they share some features with nerve cells and hormone-making cells. Merkel cells are found mainly at the base of the epidermis, which is the top layer of the skin. These cells are very close to nerve endings in the skin. They help us sense light touch, which lets us do things like feel the fine details on an object’s surface.
Merkel cell carcinoma starts when Merkel cells grow out of control. Because Merkel cells are a type of neuroendocrine cell, MCC is also sometimes called neuroendocrine carcinoma of the skin. Another name for MCC is trabecular carcinoma (or trabecular cancer).
Merkel cell carcinoma is a rare type of skin cancer that usually appears as a flesh-colored or bluish-red nodule, often on your face, head or neck. Merkel cell carcinoma is also called neuroendocrine carcinoma of the skin.
Merkel cell carcinoma most often develops in older people. Long-term sun exposure or a weak immune system may increase your risk of developing Merkel cell carcinoma.
MCC is much less common than most other types of skin cancer (see below), but it’s one of the most dangerous types. It’s much more likely than common skin cancers to spread to other parts of the body if not caught early, and it can be very hard to treat if it has spread.
These cancers most often start on sun-exposed parts of the skin, such as the face (the most common site), neck, and arms. But MCC can start anywhere on the body. Merkel cell tumors usually appear as firm, pink, red, or purple lumps or bumps on the skin. They are not usually painful, but they can grow quickly and can sometimes open up as ulcers or sores (see Signs and Symptoms of Merkel Cell Carcinoma).
While nearly all MCCs start on the skin, a very small portion start in other parts of the body, such as inside the nose or esophagus.
A risk factor is anything that affects your chance of getting a disease such as cancer. Different cancers have different risk factors. Some risk factors, like smoking and too much sun exposure, can be changed. Others, like your age or family history, can’t be changed.
Having a risk factor for Merkel cell carcinoma (MCC), or even several risk factors, does not mean that you will get it. Most people with risk factors never get MCC, while others with this disease may have few or no known risk factors.
There are a few known risk factors for MCC.
- Excessive exposure to natural or artificial sunlight. Being exposed to ultraviolet light, such as the light that comes from the sun or from tanning beds, increases your risk of Merkel cell carcinoma. The majority of Merkel cell carcinomas appear on skin surfaces frequently exposed to sun.
- A weakened immune system. People with weakened immune systems — including those with HIV infection, those taking drugs that suppress the immune response or those with chronic leukemias — are more likely to develop Merkel cell carcinoma.
- History of other skin cancers. Merkel cell carcinoma is associated with the development of other skin cancers, such as basal cell or squamous cell carcinoma.
- Older age. Your risk of Merkel cell carcinoma increases as you age. This cancer is most common in people older than age 50, though it can occur at any age.
- Light skin color. Merkel cell carcinoma usually arises in people who have light-colored skin. Whites are much more likely to be affected by this skin cancer than are blacks.
While exposure to sunlight isn’t proved to cause Merkel cell carcinoma, it is considered a risk factor for this cancer. Reducing your sun exposure may reduce your risk of skin cancer. Try to:
- Avoid the sun during peak hours. Avoid sun exposure as much as possible during the strongest sunlight hours of the day — typically from 10 a.m. to 4 p.m. Move your outdoor activities to a time earlier in the morning or later in the day.
- Shield your skin and eyes. Wear a wide-brimmed hat, tightly woven clothing and sunglasses with ultraviolet light (UV) protection.
- Apply sunscreen liberally and often. Use a broad-spectrum sunscreen with an SPF of at least 15. Apply sunscreen generously, and reapply every two hours — or more often if you’re swimming or perspiring.
- Watch for changes. If you notice a mole, freckle or bump that’s changing in size, shape or color, talk to your doctor. Most skin nodules never become cancer, but catching cancer in its early stages increases the chances that treatment will be successful.
Tests and procedures used to diagnose Merkel cell carcinoma include:
- Physical exam. Your doctor will examine your skin for unusual moles, freckles, pigmented spots and other growths.
- Removing a sample of suspicious skin. During a procedure called a skin biopsy, your doctor removes the tumor or a sample of the tumor from your skin. The sample is analyzed in a laboratory to look for signs of cancer.
Determining the extent
Your doctor may use the following tests to help determine whether the cancer has spread beyond your skin:
- Sentinel node biopsy. A sentinel node biopsy is a procedure to determine whether cancer has spread to your lymph nodes. This procedure involves injecting a dye near the cancer. The dye then flows through the lymphatic system to your lymph nodes.The first lymph node that receives the dye is called the sentinel node. Your doctor removes this lymph node and looks for cancerous cells under a microscope.
- Imaging tests. Your doctor may recommend a chest X-ray and a CT scan of your chest and abdomen to help determine whether the cancer has spread to other organs.Your doctor may also consider other imaging tests such as a positron emission tomography (PET) scan or an octreotide scan — a test that uses an injection of a radioactive tracer to check for the spread of cancer cells.
Infection with Merkel cell polyomavirus (MCV)
Evidence of the Merkel cell polyomavirus (MCV) can be found in the cells of most Merkel cell carcinomas. But MCV is a common virus. Most people are infected with MCV at some point (often before the age of 20), but the infection doesn’t cause symptoms, and it rarely leads to MCC. Because of this, there are no recommended screening tests or treatments for MCV infection.
MCV was first discovered in 2008, so there’s still a lot that scientists don’t know about this virus. For example, it’s not clear how people are infected with MCV, exactly how it might cause MCC, or if infection with MCV is required before MCC can develop.
Ultraviolet (UV) light exposure
Exposure to ultraviolet (UV) rays is thought to be a major risk factor for most skin cancers, including MCC. UV rays damage the DNA inside skin cells. This can lead to skin cancer if this damage affects the DNA of genes that control skin cell growth.
From the sun: Sunlight is the main source of UV rays. Most MCCs start in areas of the body often exposed to the sun, such as the face, neck, and arms. People who get a lot of sun exposure are at greater risk for MCC.
UV rays make up only a very small portion of the sun’s rays, but they are the main cause of the damaging effects of the sun on the skin.
From tanning beds: Tanning beds are another source of UV rays for some people. MCC is an uncommon cancer, and no studies have looked for a link between MCC and tanning bed use. But it stands to reason that more exposure to UV rays might increase the risk.
From psoriasis treatments: Some patients with psoriasis (a long-lasting inflammatory skin disease) are given medicines called psoralens along with UV light, which is known as PUVA treatments. This can increase the risk of developing MCC.
To learn more about the effects of UV rays on the skin and what you can do to protect yourself and your loved ones, see Skin Cancer Prevention and Early Detection.
Having light-colored skin
The risk of MCC is much higher for whites than for African Americans or Hispanics. This is probably due to the protective effect of darker skin against the damaging effects of UV rays.
The risk of MCC goes up as people get older. In fact, this cancer is very rare before the age of 50. The increased risk is probably related to skin damage caused by sun exposure over time and to the fact that people’s immune systems tend to become weaker as they get older.
Men are more likely than women to develop MCC. This might be because they tend to get more sun exposure.
Having a weakened immune system
The immune system defends the body against germs such as viruses. It also seems to help the body fight some cancers of the skin and other organs. People with weakened immune systems (from certain diseases or medical treatments) are more likely to develop some types of skin cancer, including MCC.
For example, people who get organ transplants usually are given drugs that weaken their immune system to help keep them from rejecting the new organ. This increases their risk of developing MCC. People with autoimmune diseases (such as lupus) sometimes take medicines that suppress the immune system, which might increase their risk.
People infected with HIV, the virus that causes AIDS, often have weakened immune systems and are also at increased risk for MCC.
People with some types of blood cancers, such as chronic lymphocytic leukemia (CLL) or certain lymphomas, also tend to have weakened immune systems. This can be from the cancer itself or from its treatment. People with these cancers are more likely to get MCC.
MCCs in people with weakened immune systems tend to grow faster and are more likely to be life-threatening.
Although we know some of the things that can raise a person’s risk of Merkel cell carcinoma (MCC), it’s not clear exactly how these things might cause MCC.
Cancer is caused by changes in the DNA inside of cells. DNA is the chemical in each of our cells that makes up our genes, which control how our cells function. We usually look like our parents because they are the source of our DNA. But DNA affects more than just how we look.
Some genes help control when our cells grow, divide into new cells, and die:
- Genes that help cells grow, divide, and stay alive are called oncogenes.
- Genes that keep cell growth in check by slowing down cell division or making cells die at the right time are called tumor suppressor genes.
Cancers can be caused by DNA changes that turn on oncogenes or turn off tumor suppressor genes. Changes in several different genes are usually needed for a cell to become a cancer cell.
Researchers don’t yet know all of the DNA changes that can result in MCC, but they have found that many of these cancers have changes in tumor suppressor genes.
MCC does not seem to run in families, so the DNA changes that lead to MCC are not likely to be inherited from a person’s parents. Instead, these changes probably happen during the person’s life. Sometimes these changes might just be random events that happen inside cells, without having an outside cause. But sometimes the cause might be something specific, like long-term sun exposure or infection with the Merkel cell polyomavirus (MCV).
Ultraviolet (UV) radiation can damage the DNA inside skin cells. Sometimes this damage affects certain genes that control how and when cells grow and divide, which may be the first step on the path to cancer.
How MCV infection plays a role in the development of MCC is not completely clear. But researchers have found that the virus can get inside cells and cause them to make a protein that turns off tumor suppressor genes, which might lead to MCC.
The importance of MCV infection might help explain why people with weakened immune systems have a higher risk of MCC. It might be that the virus is normally kept in check (but not eliminated completely) by the immune system. A weakened immune system could allow the virus to grow and flourish, which in turn might raise the risk of MCC.
Scientists are looking for the specific DNA changes inside MCC cells to help explain what causes it. A better understanding of how damaged DNA leads to MCC might also be used to design better treatments for it.
Can Merkel Cell Carcinoma Be Prevented?
The risk of getting Merkel cell carcinoma (MCC) is low, and some risk factors for MCC, such as your age, gender, and skin color can’t be controlled. But there are things you can do that might help lower your risk. These might also lower your risk of getting more common types of skin cancer, or even some other types of cancer.
Limit your exposure to ultraviolet (UV) rays
The most important way to lower your risk of skin cancers (including MCC) is to limit your exposure to UV rays. Practice sun safety when you are outdoors.
Simply staying in the shade is one of the best ways to limit your UV exposure.
“Slip! Slop! Slap! … and Wrap”
This catchphrase can help you remember some of the key steps you can take to protect yourself from UV rays. If you are going to be in the sun:
- Slip on a shirt.
- Slop on sunscreen.
- Slap on a hat.
- Wrap on sunglasses to protect the eyes and sensitive skin around them.
Avoid tanning beds and sunlamps
Many people believe the UV rays of tanning beds are harmless. This is not true. Tanning lamps give off UV rays, which can cause long-term skin damage and can contribute to skin cancer. Most skin doctors and health organizations recommend not using tanning beds and sun lamps.
Protect children from the sun
Children need special attention, since they tend to spend more time outdoors and can burn more easily. Parents and other caregivers should protect children from excess sun exposure by using the steps above. Children need to be taught about the dangers of too much sun exposure as they become more independent.
Avoid weakening your immune system (when possible)
Having a weakened immune system increases the risk of getting MCC, as well as other types of skin cancer.
Infection with HIV, the virus that causes AIDS, can weaken the immune system. Avoiding known risk factors for HIV infection, such as intravenous (IV) drug use and having unprotected sex with many partners, can also lower your risk of getting MCC and many other types of cancer. (For more information, see HIV Infection, AIDS, and Cancer.)
Some people need to take medicines to suppress their immune system. This includes people who have had organ transplants and some people with autoimmune diseases. People with cancer also sometimes need to take medicines such as chemotherapy that can lower their immune function. For these people, the benefit from taking these medicines will likely far outweigh the small overall increased risk of getting MCC.
You can play an important role in finding skin cancer early. Learn the patterns of moles, blemishes, freckles, and other marks on your skin so that you’ll notice any changes.
It’s important to check all over your skin, preferably once a month. Self-exams are best done in a well-lit room in front of a full-length mirror. Use a hand-held mirror for areas that are hard to see, such as the backs of your thighs.
Examine all areas, including your palms and soles, scalp, ears, nails, and your back. (For a more thorough description of a skin self-exam, see Skin Cancer: Prevention and Early Detection.) A friend or family member can also help you with these exams, especially for those hard-to-see areas, such as your scalp and back.
Be sure to show your doctor any areas that concern you and have them look at areas that may be hard for you to see. Any spots on the skin that are new or changing in size, shape, or color should be seen by a doctor promptly. If you can’t see your doctor right away, you might want to take good close-up photos of the area so your doctor can see if the area is changing when you do get an appointment.
Any unusual sore, lump, blemish, marking, or change in the way an area of the skin looks or feels may be a sign of skin cancer or a warning that it might occur. The area might become red, swollen, scaly, crusty, or begin oozing or bleeding. It may feel itchy, tender, or painful.
Merkel cell tumors usually look like firm, pink, red, or purple lumps or bumps on sun-exposed areas of the skin. They are not usually painful, but they can grow quickly and can sometimes open up as ulcers or sores. (See Signs and Symptoms of Merkel Cell Carcinoma for a more detailed description of what to look for.)
Exam by a health care professional
Some doctors and other health care professionals will examine your skin as part of your routine health check-up.
Having regular skin exams is especially important for people who are at high risk of MCC or other skin cancers, such as people with reduced immunity (for example, those who have had an organ transplant). Talk to your doctor about how often you should have your skin examined.
Signs and Symptoms
Merkel cell carcinoma (MCC) usually starts on areas of skin exposed to the sun, especially the face, neck, arms, and legs, but it can occur anywhere on the body. It often first appears as a single pink, red, or purple bump that is not usually painful. Sometimes the skin on the top of the tumor might break open and bleed.
These tumors can grow quickly. They might spread as new lumps in the surrounding skin. They might also reach nearby lymph nodes (small collections of immune system cells throughout the body). Over time, the lymph nodes might grow large enough to be seen or felt as lumps under the skin (usually in the neck or under the arm).
Merkel cell carcinoma is not common, and it can look like many other, more common types of skin cancer or other skin problems when it first appears. Because of this, doctors do not usually suspect MCC at first, and the diagnosis is often made only after the tumor is biopsied.
It’s very important to have any new, growing, or changing lumps, bumps, or spots on your skin checked by a doctor as soon as possible so that the cause can be found and treated, if needed. The earlier any type of skin cancer is found, the more likely it can be treated effectively.
Tests for Merkel Cell
Most skin cancers, including Merkel cell carcinoma (MCC), are brought to a doctor’s attention because of signs or symptoms a person is having.
If you have an abnormal area that might be skin cancer, your doctor will examine it and might do tests to find out if it’s cancer or some other skin condition. If there’s a chance the skin cancer has spread to other areas of the body, other tests might be done as well.
Medical history and physical exam
Usually the first step is for your doctor to ask about your symptoms, such as when the mark on the skin first appeared, if it has changed in size or appearance, and if it has been painful, itchy, or bleeding. You might also be asked about your possible risk factors for skin cancer (including sun exposure and immune system problems) and if you or anyone in your family has had skin cancer.
During the physical exam, the doctor will note the size, shape, color, and texture of the area(s) in question, and if it is bleeding, oozing, or crusting. The rest of your body may be checked for spots that could be related to skin cancer.
The doctor may also feel the nearby lymph nodes, which are bean-sized collections of immune system cells under the skin in certain areas. Merkel cell carcinomas (and some other skin cancers) can spread to lymph nodes. When this happens, the lymph nodes might be felt as lumps under the skin.
If you are being seen by your primary doctor and skin cancer is suspected, you may be referred to a dermatologist (a doctor who specializes in skin diseases), who will look at the area more closely.
Along with a standard physical exam, some dermatologists use a technique called dermatoscopy (also known as dermoscopy, epiluminescence microscopy [ELM] or surfacemicroscopy) to see spots on the skin more clearly. The doctor uses a dermatoscope, which is a special magnifying lens and light source held near the skin. Sometimes a thin layer of alcohol or oil is used with this instrument. The doctor may take a digital photo of the spot.
If the doctor thinks that a suspicious area might be MCC (or another type of skin cancer), he or she will remove it and send it to a lab to have it looked at with a microscope. This is called a skin biopsy.
There are different ways to do a skin biopsy. The doctor will choose one based on the suspected type of skin cancer, where it is on your body, its size, and other factors. Different methods can result in different scars, so ask your doctor about possible scarring before the biopsy is done.
Skin biopsies are done using a local anesthetic (numbing medicine), which is injected into the area with a very small needle. You will probably feel a small prick and a little stinging as the medicine is injected, but you should not feel any pain during the biopsy.
Shave (tangential) biopsy
For this type of biopsy, the doctor shaves off the top layers of the skin with a small surgical blade. Bleeding from the biopsy site is then stopped by applying an ointment, a chemical that stops bleeding, or a small electrical current to cauterize the wound.
A shave biopsy is useful in diagnosing many types of skin diseases, especially if the doctor thinks an abnormal area is unlikely to be a serious skin cancer such as MCC or melanoma. A thin shave biopsy is generally not used if the doctor strongly suspects MCC (or melanoma), because the biopsy often does not go deep enough to get below the tumor. On the other hand, a deeper shave biopsy can be useful if done properly.
For a punch biopsy, the doctor uses a tool that looks like a tiny round cookie cutter to remove a deeper sample of skin. The doctor rotates the punch biopsy tool on the skin until it cuts through all the layers of the skin. The sample is removed and the edges of the biopsy site are often stitched together.
Incisional and excisional biopsies
To examine a tumor that might have grown into deeper layers of the skin, the doctor may use an incisional or excisional biopsy. For these types of biopsies, a surgical knife is used to cut through the full thickness of skin. A wedge or sliver of skin is removed for examination, and the edges of the wound are usually stitched together.
An incisional biopsy removes only a portion of the tumor. An excisional biopsy removes the entire tumor, and is usually the preferred method of biopsy for a suspected MCC if it can be done. But this is not always possible, so other types of biopsies may be needed.
Lymph node biopsy
MCC often spreads to nearby lymph nodes early in the course of the disease, so it’s very important for the doctor to find out if these nodes contain cancer cells. If MCC has already been diagnosed on the skin, nearby lymph nodes will usually be biopsied to see if the cancer has spread to them.
The type of biopsy used depends on how likely it is that the cancer has reached the nearby lymph nodes:
- If the nearby lymph nodes feel normal on physical exams and look normal on imaging tests, a sentinel lymph node biopsy is likely to be done.
- If exams or imaging tests suggest that nearby lymph nodes might contain cancer (for example, if the nodes are larger than normal), then a needle biopsy is more likely to be done.
Sentinel lymph node biopsy (SLNB)
A sentinel lymph node biopsy can be used to find the lymph nodes that are likely to be the first place the MCC would go if it has spread. These lymph nodes are called sentinel nodes.
To find the sentinel lymph node (or nodes), a doctor injects a small amount of a radioactive substance into the area of the cancer. After giving the substance time to travel to the lymph node areas near the tumor, the doctor uses a special camera (and sometimes a handheld scanner) to “see” the radioactive substance where it collects in one or more sentinel lymph nodes. Once the radioactive area has been marked, the patient is taken to where the surgery will be done, and a blue dye is injected in the same place the radioactive substance was injected. A small incision is then made in the marked area, and the lymph nodes are then checked to find which one(s) became radioactive and turned blue. These sentinel nodes are removed and looked at with a microscope for cancer cells.
For more on this test and what the results could mean, see Surgery for Merkel Cell Carcinoma.
If a lymph node near a Merkel cell carcinoma is abnormally large, the doctor can use a needle biopsy to find out if the cancer has spread to the node. Needle biopsies are not as invasive as some other types of biopsies, but they may not always provide enough of a sample to find cancer cells.
There are 2 main types of needle biopsies.
- In a fine needle aspiration (FNA) biopsy, the doctor uses a syringe with a very thin, hollow needle (thinner than the ones used for blood tests) to withdraw (aspirate) cells and small pieces of tissue.
- In a core biopsy, a larger needle is used to remove one or more small cylinders (cores) of tissue. Core biopsies remove larger samples than FNA biopsies.
With either type of biopsy, a local anesthetic is sometimes used to numb the area first. These biopsies rarely cause much discomfort and do not usually leave a scar.
If the lymph node is just under the skin, the doctor can often feel it well enough to guide the needle into it. For a suspicious lymph node deeper in the body, an imaging test such as ultrasound or a CT scan is often used to guide the needle into place.
Surgical (excisional) lymph node biopsy
This type of biopsy might be done if a lymph node’s size suggests the cancer has spread there but a needle biopsy of the node has not been done (or if it did not find any cancer cells, but the doctor still suspects the cancer has spread there).
In this procedure, the doctor removes the enlarged lymph node through a small incision (cut) in the skin. This can often be done in a doctor’s office or outpatient surgical center. A local anesthetic (numbing medicine) is generally used if the lymph node is near the surface of the body, but a person may need to be sedated or even asleep (using general anesthesia) if the lymph node is deeper in the body.
Lab tests of biopsy samples
All biopsy samples will be sent to a lab, where a pathologist (a doctor who is specially trained to diagnose disease) will look at them under a microscope for MCC (or other types of cancer). Often, skin samples are sent to a dermatopathologist, a doctor who has special training in looking at skin samples.
If the doctor can’t tell for sure if the sample contains MCC just by looking at it, special lab tests may be done on the cells to try to confirm the diagnosis. One of the tests often used for MCC is immunohistochemistry (IHC), which looks for certain proteins on the cancer cells, such as CK-20.
If MCC is found, the pathologist will also look at certain important features such as the tumor thickness, mitotic rate (the portion of cells that are actively dividing), and whether the tumor has invaded the tiny blood vessels or lymph vessels in the sample. These features could help determine a person’s prognosis (outlook).
Imaging tests use x-rays, magnetic fields, or radioactive substances to create pictures of the inside of the body. They are often used to see if MCC has spread to lymph nodes or to other organs in the body.
Imaging tests can also be done to help determine how well treatment is working or to look for possible signs of cancer coming back (recurring) after treatment.
Computed tomography (CT) scan
The CT scan uses x-rays to make detailed, cross-sectional images of your body. Unlike a regular x-ray, CT scans can show the detail in soft tissues (such as internal organs). This test can show if any lymph nodes are enlarged or if other organs have suspicious spots, which might be from the spread of MCC.
CT-guided needle biopsy: CT scans can also be used to help guide a biopsy needle into a suspicious area within the body.
Magnetic resonance imaging (MRI) scan
MRI scans use radio waves and strong magnets instead of x-rays to create detailed images of parts of your body. This test can help tell if any lymph nodes are enlarged or if other organs have suspicious spots, which might be due to the spread of MCC. MRI scans are also very helpful in looking at the brain and spinal cord.
Positron emission tomography (PET) scan
A PET scan can help show if the cancer has spread to lymph nodes or other parts of the body. This test looks for areas where cells are growing quickly (which might be a sign of cancer), rather than just showing if areas look abnormal based on their size or shape.
For this test, you are injected with a slightly radioactive form of sugar, which collects mainly in cancer cells. A special camera is then used to create a picture of areas of radioactivity in the body.
PET/CT scan: Many centers have special machines that can do both a PET and CT scan at the same time. This lets the doctor compare areas of higher radioactivity on the PET scan with the more detailed appearance of that area on the CT scan.
The stage of a cancer describes how widespread it is. For Merkel cell carcinoma (MCC), this includes its size and location, whether it has grown into nearby tissues or bones, whether it has spread to nearby lymph nodes or any other organs, and certain other factors.
The stage is based on the results of physical exams, any biopsies that have been done (including sentinel lymph node biopsy), and any imaging tests (CT, MRI, PET/CT scan, etc.) that have been done. These tests are described in Tests for Merkel Cell Carcinoma.
The stage of the cancer is very important in planning treatment and estimating your prognosis (outlook).
Understanding the stage of your Merkel Cell Carcinoma
The staging system most often used for MCC is the American Joint Commission on Cancer (AJCC) TNM system, which is based on 3 key pieces of information:
- T stands for the main (primary) tumor (its size and if it has grown into nearby tissues such as muscles or bones).
- N stands for spread to nearby lymph nodes (small bean-sized collections of immune system cells, to which cancers often spread first).
- M is for metastasis (spread to distant organs). The most common sites of spread of MCC are the liver, lungs, bones, and brain, as well as distant lymph nodes.
The possible values for T are:
TX: The main (primary) tumor cannot be assessed.
T0: No evidence of primary tumor. (For example, the cancer was first found in the lymph nodes, but the main tumor itself can’t be found.)
Tis: Carcinoma in situ: the tumor is still confined to the epidermis, the outermost skin layer. (This is very rare for MCC.)
T1: The tumor is no more than 2 centimeters (cm) across (about 4/5 inch).
T2: The tumor is larger than 2 cm across, but it is no more than 5 cm (about 2 inches) across.
T3: The tumor is larger than 5 cm across.
T4: The tumor has grown into nearby tissues such as muscles, bones, or cartilage.
It’s important to know if the cancer has spread to nearby lymph nodes. Many times this can happen without the lymph nodes becoming enlarged (or otherwise being abnormal), so a sentinel lymph node biopsy is an important part of staging for most patients. The possible values for N depend in part on whether or not a lymph node biopsy was done:
NX: Nearby lymph nodes cannot be assessed.
N0: No spread to nearby lymph nodes.
cN0: The nearby lymph nodes do not feel or look abnormal (including on imaging tests), but the nodes have not been biopsied to check for cancer cells.
pN0: The nearby lymph nodes have been biopsied and no cancer was found in them.
N1a: The cancer has spread to nearby lymph nodes, but this was found during a lymph node biopsy and was not noticed on exams or imaging tests.
N1b: The cancer has spread to nearby lymph nodes, which was noticed on exams or imaging tests (and then confirmed by biopsy).
N2: The cancer has spread toward a nearby lymph node area without reaching the lymph nodes. This is called in transit metastasis.
The M values are:
M0: No spread to distant organs.
M1a: The cancer has spread to other areas of skin, to tissues under the skin, or to distant lymph nodes.
M1b: The cancer has spread to the lungs.
M1c: The cancer has spread to any other organ(s).
Stages of Merkel Cell Carcinoma
Once the T, N, and M groups have been determined, they are combined to give an overall stage, using 0 and the Roman numerals I to IV (1 to 4). Some stages are divided further using capital letters.
Tis, N0, M0: The MCC is in situ, meaning that it is still only in the epidermis (Tis). It has not been found in nearby lymph nodes (N0) or in distant organs (M0).
T1, pN0, M0: The main tumor is no more than 2 cm across (T1). Cancer has not been found in nearby lymph nodes even after looking with a biopsy (pN0). It has not spread to distant organs (M0).
T1, cN0, M0: The main tumor is no more than 2 cm across (T1). The cancer does not seem to have spread to nearby lymph nodes, but a lymph node biopsy has not been done (cN0). It has not spread to distant organs (M0).
T2 or T3, pN0, M0: The main tumor is larger than 2 cm across (T2 or T3). Cancer has not been found in nearby lymph nodes even after looking with a biopsy (pN0). It has not spread to distant organs (M0).
T2 or T3, cN0, M0: The main tumor is larger than 2 cm across (T2 or T3). The cancer does not seem to have spread to nearby lymph nodes, but a lymph node biopsy has not been done (cN0). It has not spread to distant organs (M0).
T4, N0, M0: The main tumor has grown into nearby tissues such as muscle, bone, or cartilage (T4). The cancer has not been found in nearby lymph nodes (N0) or distant organs (M0).
Any T, N1a, M0: The main tumor can be of any size and may or may not have grown into nearby tissues (any T). The cancer has spread to nearby lymph nodes, but this was found during a lymph node biopsy and was not noticed on exams or imaging tests (N1a). There is no distant spread (M0).
Any T, N1b or N2, M0: The main tumor can be of any size and may or may not have grown into nearby tissues (any T). The cancer has spread to nearby lymph nodes, which was noticed on exams or imaging tests and then confirmed by biopsy (N1b), OR the cancer has spread toward a nearby lymph node area without reaching the lymph nodes (N2). There is no distant spread (M0).
Any T, any N, M1(a, b, or c): The main tumor can be of any size and may or may not have grown into nearby tissues (any T). The cancer may or may not have spread to nearby lymph nodes (any N). The cancer has spread to other parts of the body, such as areas of skin, tissues under the skin, distant lymph nodes, or other organs in the body (M1).
In general, people with lower stage cancers tend to have a better outlook for a cure or long-term survival, but other factors can also come into play. The staging of MCC can be complex, so be sure to ask your doctor if you have any questions about the stage of your cancer.
Survival rates tell you what portion of people with the same type and stage of cancer are still alive a certain amount of time (usually 5 years) after they were diagnosed. They can’t tell you how long you will live, but they may help give you a better understanding about how likely it is that your treatment will be successful. Some people will want to know the survival rates for their cancer, and some people won’t. If you don’t want to know, you don’t have to.
5-year survival rate
Statistics on the outlook for a certain type and stage of cancer are often given as 5-year survival rates, but many people live longer – often much longer. The 5-year survival rate is the percentage of people who live at least 5 years after being diagnosed with cancer. For example, a 5-year survival rate of 70% means that an estimated 70 out of 100 people who have that cancer are still alive 5 years after being diagnosed. Keep in mind, however, that many of these people live much longer than 5 years after diagnosis.
Relative survival rates are a more accurate way to estimate the effect of cancer on survival. These rates compare people with Merkel cell carcinoma (MCC) to people in the overall population. For example, if the 5-year relative survival rate for a specific stage of MCC is 60%, it means that people who have that stage of cancer are, on average, about 60% as likely as people who don’t have that cancer to live for at least 5 years after being diagnosed.
But remember, all survival rates are estimates – your outlook can vary based on a number of factors specific to you.
Survival rates by stage
The following survival rates are based on the outcomes of nearly 3,000 patients diagnosed with MCC from 1986 to 2000 and recorded in the National Cancer Data Base.
Stage IA: The 5-year relative survival rate is about 80%.
Stage IB: The 5-year relative survival rate is about 60%.
Stage IIA: The 5-year relative survival rate is about 60%.
Stage IIB: The 5-year relative survival rate is about 50%.
Stage IIC: The 5-year relative survival rate is about 50%.
Stage IIIA: The 5-year relative survival rate is about 45%.
Stage IIIB: The 5-year relative survival rate is about 25%.
Stage IV: The 5-year relative survival rate is about 20%.
Remember, these survival rates are only estimates – they can’t predict what will happen to any individual person. We understand that these statistics can be confusing and may lead you to have more questions. Talk to your doctor to better understand your specific situation.
Other factors affecting survival
Factors other than stage can also affect survival. For example:
- People who have weakened immune systems, such as those who have had organ transplants or who are infected with HIV, tend to have a worse outlook.
- Older age has been linked with a less favorable outlook.
- Where the tumor is on the body can also affect outlook. For example, tumors on the arms tend to have a better outlook than tumors in other areas.
Based on the stage of the cancer and other factors, your treatment options might include:
- Radiation therapy
Sometimes more than one type of treatment is used. Your treatment options will depend on the stage (extent) of the cancer, as well as other factors such as your overall health and personal preferences.
- Surgery. During surgery, your doctor removes the tumor along with a border of normal skin surrounding the tumor. If there’s evidence that the cancer has spread to lymph nodes in the area of the skin tumor, those lymph nodes are removed (lymph node dissection).The surgeon most often uses a scalpel to cut away the cancer. In some cases, your doctor may use a procedure called Mohs surgery.During Mohs surgery, thin layers of tissue are methodically removed and analyzed under the microscope to see whether they contain cancer cells. If cancer is found, the surgical process is repeated until cancer cells are no longer visible in the tissue. This type of surgery takes out less normal tissue — thereby reducing scarring — but ensures a tumor-free border of skin.
- Radiation therapy. Radiation therapy involves directing high-energy beams, such as X-rays, at cancer cells. During radiation treatment, you’re positioned on a table and a large machine moves around you, directing the beams to precise points on your body.Radiation therapy is sometimes used after surgery to destroy any cancer cells that remain after the tumor is removed.Radiation also may be used as the sole treatment in people who choose not to undergo surgery. Radiation can also be used to treat areas where the cancer has spread.
- Chemotherapy. Chemotherapy uses drugs to kill the cancer cells. Chemotherapy drugs can be administered through a vein in your arm or taken as a pill or both.Your doctor may recommend chemotherapy if your Merkel cell carcinoma has spread to your lymph nodes or other organs in your body, or if it has returned despite treatment.
Which doctors treat MCC?
Depending on your options, you may have different types of doctors on your treatment team. These doctors may include:
- A dermatologist: a doctor who treats diseases of the skin
- A surgical oncologist (or oncologic surgeon): a doctor who uses surgery to treat cancer
- A medical oncologist: a doctor who treats cancer with medicines such as chemotherapy and immunotherapy.
- A radiation oncologist: a doctor who treats cancer with radiation therapy
Many other specialists might be part of your treatment team as well, including physician assistants (PAs), nurse practitioners (NPs), nurses, nutrition specialists, social workers, and other health professionals. To learn more about who may be on your cancer care team, see Health Professionals Associated With Cancer Care.
Making treatment decisions
It’s important to discuss all of your treatment options as well as their possible side effects with your treatment team to help make the decision that best fits your needs. Some important things to consider include:
- Your age and overall health
- The stage (extent) and location of your cancer
- The likelihood that treatment will cure your cancer (or help in some other way)
- Your feelings about the possible side effects from treatment
If there is anything you don’t understand, ask to have it explained. See What Should You Ask Your Cancer Care Team About Merkel Cell Carcinoma? for some questions to ask.
Getting a second opinion
MCC is not common, so most doctors are unlikely to have seen or treated many cases. Even at major medical centers, where doctors are more likely to have experience with MCC, not all doctors agree on the best way to treat these cancers. If time allows, getting a second opinionfrom a team of experts is often a good idea. It can give you more information and help you feel good about the treatment plan that you choose.
Thinking about taking part in a clinical trial
Clinical trials are carefully controlled research studies that are done to get a closer look at promising new treatments or procedures. Clinical trials are one way to get state-of-the art cancer treatment. Sometimes they may be the only way to get access to newer treatments. They are also the best way for doctors to learn better methods to treat cancer. Still, they are not right for everyone.
If you would like to learn more about clinical trials that might be right for you, start by asking your doctor if your clinic or hospital conducts clinical trials. You can also call our clinical trials matching service at 1-800-303-5691 for a list of studies that meet your medical needs, or see the Clinical Trials section on our website to learn more.
Considering complementary and alternative methods
You may hear about alternative or complementary methods that your doctor hasn’t mentioned to treat your cancer or relieve symptoms. These methods can include vitamins, herbs, and special diets, or other methods such as acupuncture or massage, to name a few.
Complementary methods refer to treatments that are used along with your regular medical care. Alternative treatments are used instead of a doctor’s medical treatment. Although some of these methods might be helpful in relieving symptoms or helping you feel better, many have not been proven to work. Some might even be dangerous.
Be sure to talk to your cancer care team about any method you are thinking about using. They can help you learn what is known (or not known) about the method, which can help you make an informed decision. See the Complementary and Alternative Medicine section of our website to learn more.
Choosing to stop treatment or choosing no treatment at all
For some people, when treatments have been tried and are no longer controlling the cancer, it could be time to weigh the benefits and risks of continuing to try new treatments. Whether or not you continue treatment, there are still things you can do to help maintain or improve your quality of life. Learn more in If Cancer Treatments Stop Working.
Some people, especially if the cancer is advanced, might not want to be treated at all. There are many reasons you might decide not to get cancer treatment, but it’s important to talk this through with your doctors before you make this decision. Remember that even if you choose not to treat the cancer, you can still get help for pain or other symptoms.
Help getting through cancer treatment
Your cancer care team will be your first source of information and support, but there are other resources for help when you need it. Hospital- or clinic-based support services can be an important part of your care. These might include nursing or social work services, financial aid, nutritional advice, rehab, or spiritual help.
The American Cancer Society also has programs and services – including rides to treatment, lodging, support groups, and more – to help you get through treatment. Call our National Cancer Information Center at 1-800-227-2345 and speak with one of our trained specialists on call 24 hours a day, every day.
or many people with Merkel cell carcinoma (MCC), treatment can remove or destroy the cancer. Completing treatment can be both stressful and exciting. You may be relieved to finish treatment, but find it hard not to worry about cancer growing or coming back. (When cancer comes back after treatment, it is called a recurrence.) This is very common if you’ve had cancer.
For others, MCC may never go away completely. These people may get regular treatment with radiation therapy, chemotherapy, or other treatments to try to help keep the cancer in check. Learning to live with cancer that does not go away can be difficult and very stressful.
Follow-up after Merkel cell carcinoma
Even if you have completed treatment, your doctors will still want to watch you closely. It’s very important to keep all follow-up appointments. During these visits, your doctors will ask if you are having any problems. They may also examine you and order lab tests or imaging teststo look for signs of cancer or treatment side effects.
Some treatment side effects might last a long time or might not even show up until years after you have finished treatment. Your doctor visits are a good time to ask questions and talk about any changes or problems you notice or concerns you have.
Can I lower my risk of MCC progressing or coming back?
If you have (or have had) MCC, you probably want to know if there are things you can do that might lower your risk of the cancer coming back, or of getting a new skin cancer.
At this time, not enough is known about MCC to say for sure if there are things you can do that will be helpful.
We do know that having a weakened immune system can raise the risk of dying from MCC, but this is often something people can’t do much about. For example, some people need to take immune-suppressing medicines because they’ve had an organ transplant or because they have an autoimmune disease. But for others, there may be things you can do to help keep your immune system strong. For example, it’s very important for people infected with HIV to take their medicines to help keep the infection under control.
We also know that people who have had MCC have a higher risk for developing other types of skin cancer. Because of this, it’s important to limit your exposure to UV rays (from the sun or tanning beds) and to examine your skin every month for signs of MCC coming back or possible new skin cancers. Skin cancers that are found early are typically much easier to treat than those found at a later stage. (See Skin Cancer Prevention and Early Detection for information on how to protect your skin and do a skin self-exam.)
Adopting healthy behaviors such as not smoking, eating well, being active, and staying at a healthy weight might help as well, but no one knows for sure. Still, we do know that these types of changes can have positive effects on your health that can extend beyond your risk of MCC or other cancers.
If the cancer comes back
If MCC does come back at some point, your treatment options will depend on where the cancer is, what treatments you’ve had before, and your overall health. For more information on how recurrent cancer is treated, see Treating Merkel Cell Carcinoma Based on the Extent of the Disease. For more general information on dealing with a recurrence, see our Understanding Recurrence section.
Merkel cell carcinoma usually appears as a single painless lump on sun-exposed skin.
This and other changes in the skin may be caused by Merkel cell carcinoma or by other conditions. Check with your doctor if you see changes in your skin.
Merkel cell carcinoma usually appears on sun-exposed skin as a single lump that is:
- Firm and dome-shaped or raised.
- Red or violet in color.
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