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Merkel cell carcinoma (MCC) is a rare type of skin cancer. It starts in the Merkel cells, which are usually in the top layer of the skin (the epidermis). These cells are near the nerve endings and they help us respond to touch.
MCC is very rare. Just over 1,500 people were diagnosed with MCC in England between 1999 and 2008.
Because Merkel cells are a type of neuroendocrine cell, MCC is also called a neuroendocrine tumour (NET) of the skin.
Risks and causes of MCC
There are some factors that increase your risk of developing Merkel cell carcinoma (MCC). But having a risk factor doesn’t mean that you will definitely develop MCC.
As with other types of skin cancer, long term exposure to sunlight increases your risk of getting MCC. Other factors that can increase your risk include:
- ultraviolet light (UVA) and psoralen ultraviolet light treatment (PUVA) for certain skin conditions such as psoriasis
- conditions or treatments that can weaken your immune system, including people who have had an organ transplant and people who have AIDS
- a virus called Merkel cell polyomavirus (MCPyV)
Age is a risk factor for most types of cancer, including MCC. The average age of diagnosis of MCC is around 70 years old.
Symptoms
MCC usually appears as lumps on the skin. The lumps are often bluish red in colour and less than 2 cm across, although they are sometimes larger. The skin over them is usually firm (not broken) and they don’t hurt.
MCCs are often found in the areas of the body that get the most direct sun such as the:
- head
- neck
- arms
- legs
Unfortunately, unlike the most common types of skin cancer, MCC develops rapidly over weeks or months. It can spread to other parts of the body such as the lymph nodes, lungs, liver or bones.
Tests
The main test to diagnose MCC is to take a sample of tissue (biopsy) of the area. Your doctor takes a sample of skin and sends it to the laboratory to be looked at under the microscope. You usually have a biopsy under local anaesthetic, which numbs the area.
People diagnosed with MCC will need to have further tests to see if the cancer has spread to other parts of the body. You might have:
- a chest x-ray
- an ultrasound scan
- a CT scan or PET-CT scan
Staging
The tests you have to find out the size of the MCC and whether it has spread helps your doctor stage your cancer. This helps them to decide on the best treatment.
To stage Merkel cell carcinoma, doctors usually use a staging system called TNM. TNM stands for tumour (T), node (N) and metastasis (M).
Tumour (T)
Tumour describes the size of the cancer. There are 4 categories:
- T1 means that the cancer is 2 cm or less
- T2 means that the cancer is between 2 and 5 cm
- T3 means that the cancer is more than 5 cm
- T4 means that the cancer has grown into nearby tissues such as the bone, muscle or cartilage
Node (N)
The N stage describes whether the cancer has spread to the lymph nodes. There are 4 possible stages:
- N0 means that there are no lymph nodes containing MCC cells
- N1 means that there are MCC cells in lymph nodes close to the tumour (regional lymph nodes)
- N2 means that there are MCC cells in the lymph channels (in transit metastases)
- N3 means that there are MCC cells in the lymph channels and the lymph nodes
Metastasis (M)
The M stage describes whether the cancer has spread to a different part of the body. There are 2 possible stages:
- M0 means that the cancer hasn’t spread to another part of the body
- M1 means that the cancer has spread to another part of the body such as the lungs
Treatment
A team of doctors and other skin cancer specialists discuss the best treatment and care for you. They are called a multidisciplinary team (MDT).
The treatment you have depends on:
- where the MCC started and its size
- whether it has spread
- your general health
Surgery
Surgery is the main treatment for MCC. Your surgeon removes all the cancer cells and a small amount of healthy tissue around it (a healthy margin). They send the tissue to the laboratory and a specialist doctor called a pathologist looks at it under a microscope.
The pathologist makes sure that there is a margin of healthy tissue around the cancer. You might hear your doctor use the term clear margins.
Your surgeon might also remove the lymph nodes around the cancer. This is where the cancer cells are most likely to travel first. The operation is called a lymph node dissection.
Remember to click back to return to the MCC section. The rest of the information on the skin cancer treatment section will not apply to you.
Radiotherapy
Radiotherapy uses high energy x-rays to kill cancer cells. You might have it after surgery to kill any MCC cells that might have been left behind. This is called adjuvant treatment. It lowers the risk of the cancer coming back.
You may also have radiotherapy on its own if you can’t have surgery for any reason
You usually have it once a day, Monday to Friday, for over 5 weeks.
Treatment for cancer that has spread
Treatment for MCC that has spread to other parts of the body won’t get rid of the cancer but it can control your symptoms and help you feel better. Treatment you might have includes:
Immunotherapy
Immunotherapy uses our immune system to fight cancer. It works by helping the immune system to recognise and attack cancer cells.
You might have a type of immunotherapy called avelumab (Bavencio). You have avelumab as a drip into your bloodstream every 2 weeks. You usually have treatment for as long as it helps you, and as long as you are not experiencing too many side effects.
Chemotherapy
Chemotherapy uses cytotoxic drugs to kill cancer cells. For MCC, you usually have a combination of chemotherapy drugs such as:
- carboplatin or cisplatin
- etoposide
- cyclophosphamide
- vincristine
- doxorubicin
- fluorouracil (5FU)
Research
Other immunotherapies have been looked at in clinical trials including the drugs:
- nivolumab
- pembrolizumab
- ipilimumab
You might be offered one of these drugs as part of a clinical trial. Or you might be offered a different drug.
Doctors are always trying to improve treatments and reduce the side effects. As part of your treatment, your doctor might ask you to take part in a clinical trial. This might be to test a new treatment or to look at different combinations of existing treatments.
Follow up
You have regular appointments with your doctor or nurse after treatment for MCC. You usually have them every 3 to 4 months for the first 3 years. And then every 6 months for up to 5 years.
During the follow up appointments, your doctor checks how you are. You can raise any concerns or problems you have with them.
You may have a scan such as a CT scan every year.
Coping
Coping with a diagnosis of cancer can be difficult. You might feel sad and worry about what will happen. Being well informed about your cancer and its treatment can make it easier to make decisions and cope with what happens afterwards.
