Merkel cell carcinoma (MCC)

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. This layer is called the epidermis. Merkel cells are near the nerve endings and they help us respond to touch.

Each year around 360 people are diagnosed with MCC in England. This is based on the average number of new cases diagnosed in the years 2019, 2021, and 2022.  

Because Merkel cells are a type of neuroendocrine cell, MCC is also called a neuroendocrine carcinoma (NEC) of the skin.

Risks and causes of MCC

As with other types of skin cancer, long term exposure to sunlight increases your risk of getting MCC. The risk is also higher for White people with fair skin than for Black people. There are some other factors that can increase your risk: 

• 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 . These include 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 median age of diagnosis of MCC is around 76 years old. 

Symptoms

MCC usually appears as a lump on the skin. The lump is often a blueish purple (violet) or red colour.  The skin over the lump is usually firm (not broken) and it doesn’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 to diagnose MCC

Many people start by seeing their GP. Your GP looks at your symptoms. They decide whether to refer you to a dermatologist . 

The dermatologist does a physical examination of your skin and lymph nodes . They might look closely at the skin lump with a special instrument called a dermatoscope.

The main test to diagnose MCC is to take a biopsy  of the area. Your dermatologist takes a sample of skin and sends it to the laboratory. A pathologist  looks at it under the microscope. You usually have a biopsy under local anaesthetic , which numbs the area.

If you have MCC, you will need to have further tests. These are to see if the cancer has spread to other parts of your body. You might have:

• an ultrasound scan
• a CT scan or PET-CT scan
• an MRI scan

There is a risk that MCC cells have spread to your lymph nodes so you might have tests to check these.

Your doctor may check your lymph nodes by doing an ultrasound and taking a biopsy. Or they might do a sentinel lymph node biopsy (SLNB). The sentinel lymph nodes are the first lymph nodes the cancer can reach. During a SLNB your doctor removes the sentinel nodes and sends them to the laboratory. This is to check them for cancer cells that can only be seen under a microscope.

You have a SLNB under a general anaesthetic at the same time as surgery to remove the MCC.

Staging merkel cell carcinoma (MCC)

Your stage tells you how big the cancer is, and whether it has spread. The tests you have help your doctor stage your cancer. This helps them to decide on the best treatment. 

To stage MCC, 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  - these are called regional lymph nodes
• N2 means that there are MCC cells in the lymph vessels  - these are called in transit metastases
• N3 means that there are MCC cells in the lymph vessels 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 for merkel cell carcinoma

A team of doctors and other skin cancer specialists discuss the best treatment and care for you. They are called a multidisciplinary team (MDT). MCC is quite a rare type of skin cancer. Your MDT should include doctors with experience of looking after people with MCC.

The treatment you have depends on:

• where the MCC started and its size

• whether it has spread

• your general health and well being

Surgery

Surgery is the main treatment for MCC. Your surgeon removes all the cancer cells and a small amount of healthy tissue around it. This operation is called a wide local excision (WLE). The surgeon sends the tissue to the laboratory and 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.

Removing lymph nodes

Cancer cells are most likely to travel to nearby lymph nodes first. After examining you and doing tests, your surgeon might know that there are cancer cells in the lymph nodes around the cancer. They remove these lymph nodes. The operation is called a lymph node dissection.

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 usually have it once a day, Monday to Friday, for over 5 weeks.

You may also have radiotherapy on its own as your main treatment if you can’t have surgery for any reason. 

Radiotherapy can also help control symptoms such as pain if your MCC has spread. This is called palliative radiotherapy. 

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

Research

Clinical trials have looked at other immunotherapies including the drugs:

• nivolumab
• pembrolizumab
• ipilimumab

Your doctor might offer you one of these drugs as part of a clinical trial.  Or they might offer you 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 specialist doctor or nurse after treatment for MCC. You usually have them every 3 months for the first 3 years. And then every 6 months for up to 5 years.

During the follow up appointments, your doctor examines you and checks how you are. You can raise any concerns or problems you have with them.

You might have scans such as a CT scan or PET-CT scan, depending on your situation.

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.

Talking to other people

Talking to people who have the same condition can help.

Our discussion forum Cancer Chat is a place for anyone affected by cancer. You can share experiences, stories and information with other people who know what you are going through.

The Rare Cancer Alliance offer support and information to people affected by rare cancers.