What is Merkel Cell Carcinoma?
Merkel Cell Carcinoma is a relatively rare form of skin cancer, with an incidence of around 1 per 400,000 people. It is a cancer of the Merkel Cell, a fairly scarce cell found in the skin that is thought to help with feelings of touch and hair movement.
Where is Merkel Cell Carcinoma found?
The most common site for Merkel Cell Carcinoma is on the head and neck (50%). It can also occur on the limbs (45%) and trunk (5%).
Merkel Cell Carcinoma tends to arise in later life, around 60-70 years old.
What causes Merkel Cell Carcinoma?
The exact cause is unknown, although most occur in areas exposed to sunlight, so UV is thought to play a part. In 2008 it was found that Merkel Cell Carcinoma may be associated with a virus, called Merkel Cell polyomavirus. The virus is found in 80% of Merkel Cell Carcinomas, but 80% of 50 year-olds carry the virus - so the virus seems to have a link to Merkel Cell Carcinoma, but is not the sole cause.
Immunodeficiency also plays a role, and there is an increased risk of Merkel Cell Carcinoma in illnesses such as HIV and chronic lymphocytic leukaemia, and in transplant patients.
What does Merkel Cell Carcinoma look like?
Diagnosis can be very difficult, and Merkel Cell Carcinoma usually presents as a firm, shiny, raised skin growth that may vary in colour from red to violet to blue. They usually grow rapidly, and can easily be mistaken for basal cell carcinoma, squamous cell carcinoma, or melanoma.
Occasionally, nearby lymph glands (in the armpit, neck or groin) may also be enlarged.
Usually, Merkel Cell Carcinoma is painless.
Are any tests needed for Merkel Cell Carcinoma?
To make a diagnosis of Merkel Cell Carcinoma, the specialist may need to take a small sample (biopsy) of the growth. This is usually very simple and can be performed under local anesthetic.
Occasionally the specialist may arrange an ultrasound scan, CT scan or MRI scan, to look for any evidence that the Merkel Cell Carcinoma has spread elsewhere.
What is the treatment for Merkel Cell Carcinoma?
There are a number of treatment options for Merkel Cell Carcinoma, which may be used in isolation or in combination depending on factors such as where the growth is, how advanced it is, and how fit the patient is for surgery.
Surgery - this is the most common treatment method for Merkel Cell Carcinoma. The tumour is removed with a margin of normal appearing skin around it. This margin may be 2-3cm from the tumour. Due to such large margins, reconstruction is often needed in the form of a skin graft or skin flap.
Mohs surgery - this is a form of treatment whereby samples of the Merkel cell carcinoma are removed and examined. The process is continued until all the carcinoma has been removed. Whilst some believe this to be better than 'standard' surgery, evidence is still lacking to prove this. To read more about Mohs surgery please click here.
Radiotherapy - some Merkel cell carcinomas may be treated with radiotherapy, which is generally painless. The growth itself may be irradiated instead of using surgery if the patient is not fit enough to undergo an operation, or radiotherapy may be given to the site of the Merkel Cell Carcinoma after surgical removal with the aim of reducing the risk of recurrence. Additionally, nearby lymph glands (armpit, neck, or groin) may have radiotherapy treatment if Merkel Cell Carcinoma has spread to these glands, or to try and reduce the chance of spread.
Sentinel node biopsy - this is where special dye is injected around the Merkel Cell Carcinoma, which is then taken up by the skin and drained to nearby lymph glands. The surgeon is then able to identify which lymph gland drains the particular bit of skin where the tumour is, and this gland is removed. This helps to check if the Merkel Cell Carcinoma has spread to the glands or not. Whilst this seems promising, there is little evidence that a sentinel node biopsy is of any great help in treating Merkel Cell Carcinoma and further research is ongoing.
Lymph node dissection - this is where all the glands in the nearby area are removed (armpit, neck or groin). This is usually performed only if the Merkel Cell Carcinoma has been found to have spread to the glands, and not if the glands are thought to be uninvolved (as radiotherapy may be used instead).
Chemotherapy - this is usually reserved for patients who have spread of their Merkel Cell Carcinoma. Unfortunately, response is limited and chemotherapy currently has a limited role in this field.
The final treatment course will often depend on the carcinoma type, body area and of course patient preference. Your specialist will be able to discuss treatment options with you.
What is the prognosis of Merkel Cell Carcinoma?
Merkel Cell Carcinoma can be aggressive, and can spread to the lymph glands and onwards to other parts of the body.
If at diagnosis the carcinoma has not been found to spread, then approximately 65% will live past 5 years. This drops to around 45% if the carcinoma is found in the glands. If the Merkel Cell Carcinoma has spread to other parts of the body, then average survival is approximately 9 months.
I think I have a Merkel Cell Carcinoma - what should I do?
As described above, Merkel Cell Carcinoma is very rare. If you think you may have one though, or indeed any other worrying skin growth, then you should urgently seek medical advise.
You may also wish to read our articles on Basal cell carcinoma, Squamous cell carcinoma, or melanoma
To see pictures of skin cancers, please click here
The information provided is as a guide only and you should discuss matters fully with your specialist before deciding the right procedure for you. Please also read our disclaimer