General Information About Merkel Cell Carcinoma
Merkel cell carcinoma is a very rare disease in which malignant (cancer) cells form in the skin.
Merkel cells are found in the top layer of the skin. These cells are very close to the nerve endings that receive the sensation of touch. Merkel cell carcinoma, also called neuroendocrine carcinoma of the skin or trabecular cancer, is a very rare type of skin cancer that forms when Merkel cells grow out of control. Merkel cell carcinoma starts most often in areas of skin exposed to the sun, especially the head and neck, as well as the arms, legs, and trunk.
Anatomy of the skin showing the epidermis, dermis, and subcutaneous tissue. Merkel cells are in the layer of basal cells at the deepest part of the epidermis and are connected to nerves.
Merkel cell carcinoma tends to grow quickly and to metastasize (spread) at an early stage. It usually spreads first to nearby lymph nodes and then may spread to lymph nodes or skin in distant parts of the body, lungs, brain, bones, or other organs.
Sun exposure and having a weak immune system can affect the risk of Merkel cell carcinoma.
Anything that increases your risk of getting a disease is called a risk factor. Having a risk factor does not mean that you will get cancer; not having risk factors doesn't mean that you will not get cancer. Talk with your doctor if you think you may be at risk. Risk factors for Merkel cell carcinoma include the following:
- Being exposed to a lot of natural sunlight.
- Being exposed to artificial sunlight, such as from tanning beds or psoralen and ultraviolet A (PUVA) therapy for psoriasis.
- Having an immune system weakened by disease, such as chronic lymphocytic leukemia or HIV infection.
- Taking drugs that make the immune system less active, such as after an organ transplant.
- Having a history of other types of cancer.
- Being older than 50 years, male, or white.
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:
- Fast-growing.
- Painless.
- Firm and dome-shaped or raised.
- Red or violet in color.
Tests and procedures that examine the skin are used to detect (find) and diagnose Merkel cell carcinoma.
The following tests and procedures may be used:
- Physical exam and history: An exam of the body to check general signs of health, including checking for signs of disease, such as lumps or anything else that seems unusual. A history of the patient's health habits and past illnesses and treatments will also be taken.
- Full-body skin exam: A doctor or nurse checks the skin for bumps or spots that look abnormal in color, size, shape, or texture. The size, shape, and texture of the lymph nodes will also be checked.
- Skin biopsy: The removal of skin cells or tissues so they can be viewed under a microscope by a pathologist to check for signs of cancer.
Certain factors affect prognosis (chance of recovery) and treatment options.
The prognosis (chance of recovery) and treatment options depend on the following:
- The stage of the cancer (the size of the tumor and whether it has spread to the lymph nodes or other parts of the body).
- Where the cancer is in the body.
- Whether the cancer has just been diagnosed or has recurred (come back).
- The patient's age and general health.
Prognosis also depends on how deeply the tumor has grown into the skin.
Stages of Merkel Cell Carcinoma
After Merkel cell carcinoma has been diagnosed, tests are done to find out if cancer cells have spread to other parts of the body.
The process used to find out if cancer has spread to other parts of the body is called staging. The information gathered from the staging process determines the stage of the disease. It is important to know the stage in order to plan treatment.
The following tests and procedures may be used in the staging process:
- CT scan (CAT scan): A procedure that makes a series of detailed pictures of areas inside the body, taken from different angles. The pictures are made by a computer linked to an x-ray machine. A dye may be injected into a vein or swallowed to help the organs or tissues show up more clearly. A CT scan of the chest and abdomen may be used to check for primary small cell lung cancer, or to find Merkel cell carcinoma that has spread. A CT scan of the head and neck may also be used to find Merkel cell carcinoma that has spread to the lymph nodes. This procedure is also called computed tomography, computerized tomography, or computerized axial tomography.
- MRI (magnetic resonance imaging): A procedure that uses a magnet, radio waves, and a computer to make a series of detailed pictures of areas inside the body. This procedure is also called nuclear magnetic resonance imaging (NMRI).
- PET scan (positron emission tomography scan): A procedure to find malignant tumor cells in the body. A small amount of radioactive glucose (sugar) is injected into a vein. The PET scanner rotates around the body and makes a picture of where glucose is being used in the body. Malignant tumor cells show up brighter in the picture because they are more active and take up more glucose than normal cells do.
- Lymph node biopsy: There are two main types of lymph node biopsy used to stage Merkel cell carcinoma.
- Sentinel lymph node biopsy: The removal of the sentinel lymph node during surgery. The sentinel lymph node is the first lymph node to receive lymphatic drainage from a tumor. It is the first lymph node the cancer is likely to spread to from the tumor. A radioactive substance and/or blue dye is injected near the tumor. The substance or dye flows through the lymph ducts to the lymph nodes. The first lymph node to receive the substance or dye is removed. A pathologist views the tissue under a microscope to look for cancer cells. If cancer cells are not found, it may not be necessary to remove more lymph nodes.
Sentinel lymph node biopsy of the skin. A radioactive substance and/or blue dye is injected near the tumor (first panel). The injected material is detected visually and/or with a probe that detects radioactivity (middle panel). The sentinel nodes (the first lymph nodes to take up the material) are removed and checked for cancer cells (last panel). - Lymph node dissection: A surgical procedure in which the lymph nodes are removed and a sample of tissue is checked under a microscope for signs of cancer. For a regional lymph node dissection, some of the lymph nodes in the tumor area are removed. For a radical lymph node dissection, most or all of the lymph nodes in the tumor area are removed. This procedure is also called lymphadenectomy.
- Immunohistochemistry: A test that uses antibodies to check for certain antigens in a sample of tissue. The antibody is usually linked to a radioactive substance or a dye that causes the tissue to light up under a microscope. This type of test may be used to tell the difference between different types of cancer.
There are three ways that cancer spreads in the body.
Cancer can spread through tissue, the lymph system, and the blood:
- Tissue. The cancer spreads from where it began by growing into nearby areas.
- Lymph system. The cancer spreads from where it began by getting into the lymph system. The cancer travels through the lymph vessels to other parts of the body.
- Blood. The cancer spreads from where it began by getting into the blood. The cancer travels through the blood vessels to other parts of the body.
Cancer may spread from where it began to other parts of the body.
When cancer spreads to another part of the body, it is called metastasis. Cancer cells break away from where they began (the primary tumor) and travel through the lymph system or blood.
- Lymph system. The cancer gets into the lymph system, travels through the lymph vessels, and forms a tumor (metastatic tumor) in another part of the body.
- Blood. The cancer gets into the blood, travels through the blood vessels, and forms a tumor (metastatic tumor) in another part of the body.
The metastatic tumor is the same type of cancer as the primary tumor. For example, if Merkel cell carcinoma spreads to the liver, the cancer cells in the liver are actually cancerous Merkel cells. The disease is metastatic Merkel cell carcinoma, not liver cancer.
The following stages are used for Merkel cell carcinoma:
Pea, peanut, walnut, and lime show tumor sizes.
Stage 0 (carcinoma in situ)
In stage 0, the tumor is a group of abnormal cells that remain in the place where they first formed and have not spread. These abnormal cells may become cancer and spread to lymph nodes or distant parts of the body.
Stage IA
In stage IA, the tumor is 2 centimeters or smaller at its widest point and no cancer is found when the lymph nodes are checked under a microscope.
Stage IB
In stage IB, the tumor is 2 centimeters or smaller at its widest point and no swollen lymph nodes are found by a physical exam or imaging tests.
Stage IIA
In stage IIA, the tumor is larger than 2 centimeters and no cancer is found when the lymph nodes are checked under a microscope.
Stage IIB
In stage IIB, the tumor is larger than 2 centimeters and no swollen lymph nodes are found by a physical exam or imaging tests.
Stage IIC
In stage IIC, the tumor may be any size and has spread to nearby bone, muscle, connective tissue, or cartilage. It has not spread to lymph nodes or distant parts of the body.
Stage IIIA
In stage IIIA, the tumor may be any size and may have spread to nearby bone, muscle, connective tissue, or cartilage. Cancer is found in the lymph nodes when they are checked under a microscope.
Stage IIIB
In stage IIIB, the tumor may be any size and may have spread to nearby bone, muscle, connective tissue, or cartilage. Cancer has spread to the lymph nodes near the tumor and is found by a physical exam or imaging test. The lymph nodes are removed and cancer is found in the lymph nodes when they are checked under a microscope. There may also be a second tumor, which is either:
- Between the primary tumor and nearby lymph nodes; or
- Farther away from the center of the body than the primary tumor is.
Stage IV
In stage IV, the tumor may be any size and has spread to distant parts of the body, such as the liver, lung, bone, or brain.
Recurrent Merkel Cell Carcinoma
Recurrent Merkel cell carcinoma is cancer that has recurred (come back) after it has been treated. The cancer may come back in the skin, lymph nodes, or other parts of the body. It is common for Merkel cell carcinoma to recur.
Treatment Option Overview
There are different types of treatment for patients with Merkel cell carcinoma.
Different types of treatments are available for patients with Merkel cell carcinoma. Some treatments are standard (the currently used treatment), and some are being tested in clinical trials. A treatment clinical trial is a research study meant to help improve current treatments or obtain information on new treatments for patients with cancer. When clinical trials show that a new treatment is better than the standard treatment, the new treatment may become the standard treatment. Patients may want to think about taking part in a clinical trial. Some clinical trials are open only to patients who have not started treatment.
Three types of standard treatment are used:
Surgery
One or more of the following surgical procedures may be used to treat Merkel cell carcinoma:
- Wide local excision: The cancer is cut from the skin along with some of the tissue around it. A sentinel lymph node biopsy may be done during the wide local excision procedure. If there is cancer in the lymph nodes, a lymph node dissection also may be done.
- Lymph node dissection: A surgical procedure in which the lymph nodes are removed and a sample of tissue is checked under a microscope for signs of cancer. For a regional lymph node dissection, some of the lymph nodes in the tumor area are removed; for a radical lymph node dissection, most or all of the lymph nodes in the tumor area are removed. This procedure is also called lymphadenectomy.
Even if the doctor removes all the cancer that can be seen at the time of the surgery, some patients may be given chemotherapy or radiation therapy after surgery to kill any cancer cells that are left. Treatment given after the surgery, to lower the risk that the cancer will come back, is called adjuvant therapy.
Radiation therapy
Radiation therapy is a cancer treatment that uses high-energy x-rays or other types of radiation to kill cancer cells or keep them from growing. There are two types of radiation therapy:
- External radiation therapy uses a machine outside the body to send radiation toward the cancer.
- Internal radiation therapy uses a radioactive substance sealed in needles, seeds, wires, or catheters that are placed directly into or near the cancer.
The way the radiation therapy is given depends on the type and stage of the cancer being treated. External radiation therapy is used to treat Merkel cell carcinoma, and may also be used as palliative therapy to relieve symptoms and improve quality of life.
Chemotherapy
Chemotherapy is a cancer treatment that uses drugs to stop the growth of cancer cells, either by killing the cells or by stopping the cells from dividing. When chemotherapy is taken by mouth or injected into a vein or muscle, the drugs enter the bloodstream and can reach cancer cells throughout the body (systemic chemotherapy). When chemotherapy is placed directly into the cerebrospinal fluid, an organ, or a body cavity such as the abdomen, the drugs mainly affect cancer cells in those areas (regional chemotherapy). The way the chemotherapy is given depends on the type and stage of the cancer being treated.
New types of treatment are being tested in clinical trials.
Information about clinical trials is available from the NCI website.
Patients may want to think about taking part in a clinical trial.
For some patients, taking part in a clinical trial may be the best treatment choice. Clinical trials are part of the cancer research process. Clinical trials are done to find out if new cancer treatments are safe and effective or better than the standard treatment.
Many of today's standard treatments for cancer are based on earlier clinical trials. Patients who take part in a clinical trial may receive the standard treatment or be among the first to receive a new treatment.
Patients who take part in clinical trials also help improve the way cancer will be treated in the future. Even when clinical trials do not lead to effective new treatments, they often answer important questions and help move research forward.
Patients can enter clinical trials before, during, or after starting their cancer treatment.
Some clinical trials only include patients who have not yet received treatment. Other trials test treatments for patients whose cancer has not gotten better. There are also clinical trials that test new ways to stop cancer from recurring (coming back) or reduce the side effects of cancer treatment.
Clinical trials are taking place in many parts of the country. See the Treatment Options section that follows for links to current treatment clinical trials. These have been retrieved from NCI's listing of clinical trials.
Follow-up tests may be needed.
Some of the tests that were done to diagnose the cancer or to find out the stage of the cancer may be repeated. Some tests will be repeated in order to see how well the treatment is working. Decisions about whether to continue, change, or stop treatment may be based on the results of these tests.
Some of the tests will continue to be done from time to time after treatment has ended. The results of these tests can show if your condition has changed or if the cancer has recurred (come back). These tests are sometimes called follow-up tests or check-ups.
Treatment Options by Stage
Stage I and Stage II Merkel Cell Carcinoma
Treatment of stage I and stage II Merkel cell carcinoma may include the following:
- Surgery to remove the tumor, such as wide local excision with or without lymph node dissection.
- Radiation therapy after surgery.
- A clinical trial of a new treatment.
Check the list of NCI-supported cancer clinical trials that are now accepting patients with stage I neuroendocrine carcinoma of the skin and stage II neuroendocrine carcinoma of the skin. For more specific results, refine the search by using other search features, such as the location of the trial, the type of treatment, or the name of the drug. Talk with your doctor about clinical trials that may be right for you. General information about clinical trials is available from the NCI website.
Stage III Merkel Cell Carcinoma
Treatment of stage III Merkel cell carcinoma may include the following:
- Wide local excision with or without lymph node dissection.
- Radiation therapy.
- A clinical trial of chemotherapy.
Check the list of NCI-supported cancer clinical trials that are now accepting patients with stage III neuroendocrine carcinoma of the skin. For more specific results, refine the search by using other search features, such as the location of the trial, the type of treatment, or the name of the drug. Talk with your doctor about clinical trials that may be right for you. General information about clinical trials is available from the NCI website.
Stage IV Merkel Cell Carcinoma
Treatment of stage IV Merkel cell carcinoma may include the following as palliative treatment to relieve symptoms and improve quality of life:
- Chemotherapy.
- Surgery.
- Radiation therapy.
- A clinical trial of a new treatment.
Check the list of NCI-supported cancer clinical trials that are now accepting patients with stage IV neuroendocrine carcinoma of the skin. For more specific results, refine the search by using other search features, such as the location of the trial, the type of treatment, or the name of the drug. Talk with your doctor about clinical trials that may be right for you. General information about clinical trials is available from the NCI website.
Treatment Options for Recurrent Merkel Cell Carcinoma
Treatment of recurrent Merkel cell carcinoma may include the following:
- Wide local excision to remove a larger area of tissue than was removed in earlier surgery. A lymph node dissection may also be done.
- Radiation therapy after surgery.
- Chemotherapy.
- Radiation therapy and/or surgery as palliative treatment to relieve symptoms and improve quality of life.
Check the list of NCI-supported cancer clinical trials that are now accepting patients with recurrent neuroendocrine carcinoma of the skin. For more specific results, refine the search by using other search features, such as the location of the trial, the type of treatment, or the name of the drug. Talk with your doctor about clinical trials that may be right for you. General information about clinical trials is available from the NCI website.
To Learn More About Merkel Cell Carcinoma
For more information from the National Cancer Institute about Merkel cell carcinoma, see the following:
- Skin Cancer (Including Melanoma) Home Page
- Skin Cancer Prevention
- Skin Cancer Screening
- Sentinel Lymph Node Biopsy
For general cancer information and other resources from the National Cancer Institute, see the following:
- About Cancer
- Staging
- Chemotherapy and You: Support for People With Cancer
- Radiation Therapy and You: Support for People With Cancer
- Coping with Cancer
- Questions to Ask Your Doctor about Cancer
- For Survivors and Caregivers
About This PDQ Summary
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Physician Data Query (PDQ) is the National Cancer Institute's (NCI's) comprehensive cancer information database. The PDQ database contains summaries of the latest published information on cancer prevention, detection, genetics, treatment, supportive care, and complementary and alternative medicine. Most summaries come in two versions. The health professional versions have detailed information written in technical language. The patient versions are written in easy-to-understand, nontechnical language. Both versions have cancer information that is accurate and up to date and most versions are also available in Spanish.
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PDQ® Adult Treatment Editorial Board. PDQ Merkel Cell Carcinoma Treatment. Bethesda, MD: National Cancer Institute. Updated <MM/DD/YYYY>. Available at: https://www.cancer.gov/types/skin/patient/merkel-cell-treatment-pdq. Accessed <MM/DD/YYYY>. [PMID: 26389202]
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Last Revised: 2016-07-22
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