At Stanford Health Care, our experienced cancer care team uses a multispecialty approach to treat MCC. We offer advanced treatments, innovative therapies, and comprehensive care in a supportive environment. Our team is by your side at every step.
What is Merkel cell skin cancer?
Merkel cell skin cancer is a rapidly growing neuroendocrine cancer that most likely develops from epidermal precursor cells. About 80% of MCC cases are caused by a polyomavirus that infects the vast majority of humans during early childhood with the remaining 20% being caused by ultraviolet sun rays. While MCC can affect people of any skin tone, people with light skin tone are most commonly affected. Treatments for this type of skin cancer include surgery, radiation, and medications that destroy the cancerous cells.
How does Merkel cell skin cancer develop?
MCC usually grows on skin that has been exposed to the sun. It’s most common on skin on the face, neck, arms, and legs. People over 50 who have a weakened immune system are more likely to develop Merkel cell skin cancer.
Merkel cell skin cancer often spreads quickly. It tends to spread to nearby lymph nodes first (lymph nodes are small glands that that store infection-fighting cells). It can then spread to the liver, bones, lungs, and brain. When it’s caught early, this type of skin cancer is often treatable. Once Merkel cell skin cancer has spread, it’s much more difficult to treat.
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Merkel Cell Skin Cancer Symptoms
The first sign of a Merkel cell tumor is a lump or bump on the skin. The bump most commonly appears on the head, face, neck, arms, legs, or another area that has been exposed to the sun; however, the lump can also appear in areas that are usually covered by clothing.
At first, the bump or growth is typically:
- Firm, shiny, and shaped like a dome (the top of the growth may crack and bleed)
- Painless
- Pink, red, purple, or blue
- Smaller than a pea, but it can be larger and tends to grow quickly
Merkel Cell Skin Cancer Risk Factors
Risk factors increase your chance of developing certain cancers. Although people of all genders can develop MCC, men are twice as likely to get this type of cancer. Other risk factors for MCC include:
- Age: Merkel cell skin cancer occurs most often in people between 60 and 80 years of age. It’s very rare in people under 50.
- Extensive ultraviolet (UV) light exposure: People who have been exposed to a lot of UV light, either from the sun or a tanning bed, have an increased chance of getting MCC. UV rays damage genetic material inside cells, which can cause all types of skin cancer.
- Skin tone: People with light skin tones are much more likely to get Merkel cell skin cancer than people with dark skin tone.
People with a weakened immune system have an increased risk of developing Merkel cell skin cancer. This type of cancer is more common in people who have a compromised immune system from:
Merkel Cell Skin Cancer Stages
Doctors use a process called staging to determine if cancer has spread and, if so, how far. Staging helps doctors develop a treatment plan. When determining the stage, doctors look at many factors, including:
- Size of the original tumor and whether it has spread to the surrounding skin
- Whether cancer has spread to nearby lymph nodes and, if so, which ones
- Whether cancer has spread to other parts of the body or to organs, such as the lungs or liver
Stages of MCC include:
- Stage 0: Cancerous cells are only in the skin’s top layer. This stage is also called carcinoma in situ.
- Stage 1: The original tumor is two centimeters or smaller. Two centimeters is about the size of a peanut.
- Stage 2: The original tumor is larger than two centimeters. It may have spread to nearby structures, such as muscles and bones, but not to the lymph nodes.
- Stage 3: Cancer has spread to nearby lymph nodes, or it is approaching the lymph nodes. It may also have spread further into nearby muscles, bones, and cartilage.
- Stage 4: Cancer has spread to skin, bones, organs, and parts of the body that aren’t close to the original tumor.
- Recurrent: Cancer recurs (comes back) after treatment. It may come back in the same area or in another part of the body.
Cancer staging can be very complicated. Your doctor will explain the staging process to you and help you understand the extent of the cancer you have.
Your doctor begins by gathering a thorough health history, including any previous test results and medical records. They will ask about your symptoms, examine your skin, and feel for swollen lymph nodes. To diagnose skin cancer, your doctor may recommend tests, such as:
- Skin biopsy: During a skin biopsy, your doctor removes a small sample of your skin and sends it to a lab. The lab tests for signs of cancer. Your doctor may remove the sample by shaving off the top layers of skin (shave biopsy), or they may use a small tool to take a sample from deeper layers (punch biopsy).
- Excisional biopsy and incisional biopsy: Your doctor removes the tumor and sends it to a lab for testing. They may remove all of the tumor (excisional biopsy) or part of the tumor (incisional biopsy).
- Needle biopsy: Your doctor inserts a very thin needle (fine needle aspiration or FNA) or a wider needle (core biopsy) into a skin tumor or lymph node. They remove a sample of cells through the needle and send it to a lab to check for cancer.
- Sentinel lymph node biopsy: The sentinel node is the first lymph node to which cancer is likely to spread. Doctors use this procedure during staging to determine if Merkel cell carcinoma has spread to the lymph nodes. They inject a small amount of radioactive dye into the area around the tumor. The dye flows through the lymph channels to the sentinel node. Then, your doctor removes that node to test for signs of cancer.
Imaging tests provide detailed pictures of the inside of your body. Your doctor may order several imaging tests that use various technologies, such as:
- Computed tomography scan (CT scan): This test uses special X-ray and computer equipment to create images of bones, tissues, and organs.
- Magnetic resonance imaging scan (MRI): An MRI uses powerful magnets, radio waves, and a computer to create pictures.
- Positron emission tomography (PET scan): A PET scan is a type of nuclear medicine imaging that measures cell activity in the body. You receive a small amount of a tracer, a radioactive substance that travels through your body. The tracer detects areas of increased cell activity, called hot spots. These hot spots show up brighter on the scan, which typically indicate cancerous cells.
- PET/CT scan: The PET/CT combination provides more accurate diagnoses than the two scans performed separately.
Your doctor may take small samples of your blood to test in the lab. Blood tests provide information about your health, including how your organs are working and if cancer has spread. These tests also help your care team monitor any potential side effects of treatment.
- Circulating tumor DNA (ctDNA) test: The ctDNA blood testing is helpful for monitoring patients for cancer recurrence after initial treatment. This is a personalized test that detects MCC mutations in your blood and is a real time measurement of tumor burden in the body.
- AMERK serology test: This blood testing can detect polyomavirus antigens in about 50% of MCC patients. In the patients who have antibodies, it can used to detect a recurrence.
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