MERKEL CELL Carcinoma(MCC)

Merkel cell carcinoma is a rare, aggressive skin cancer. It appears as a painless, flesh-colored or bluish-red nodule growing on the skin.

Merkel cells are found just below the skin’s surface, on the lowest level of your top layer of skin (the epidermis). Connected to nerve endings associated with the sensation of pressure, Merkel cells play a key role in helping us identify fine details and textures by touch.

Merkel cell carcinoma is a rare aggressive skin cancer. The name was given to the cancer because of the cancer cell's resemblance under the microscope to Merkel cells.

This disease usually appears as a painless skin nodule (bump or lump) that grows very rapidly. The tumors can be skin-colored, red, or violet, most often developing in areas of skin exposed to the sun, especially the face, eyelids, head, and neck.

But these nodules can develop anywhere on the body, even areas not often exposed to sunlight.

 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.

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

As with other types of skin cancer, long term exposure to sunlight increases your risk of getting MCC. Other factors that can increase the risk include:

• ultraviolet light (UVA) and psoralen ultraviolet light treatment (PUVA) for certain skin conditions such as psoriasis
• conditions or treatments that can weaken the 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 50 years old. 

Symptoms

MCC usually appears as lumps on the skin. The lumps are often bluish red in colour and less than 1/2 an inch across, although they are sometimes larger. The skin over them is usually firm (not broken) and they do not hurt.

MCCs are often found in the areas of the body that get the most direct sun such as the:

• head
• eyelid
• 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 like 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. A sample of skin is sent to the laboratory to be looked at under the microscope. 

People diagnosed with MCC will need to have further tests to see if the cancer has spread to other parts of the body. One may have:

• a chest x-ray
• an ultrasound scan
• a CT scan or PET-CT scan

Staging

The tests determine the size of the MCC and whether it has spread helps the clinical tean stage the cancer, so as to decide on the best treatment. 

To stage Merkel cell carcinoma, doctors usually use a staging system called TNM. TNM stands for tumor (T), node (N) and metastasis (M). 

Tumor (T)

Tumor describes the size of the cancer. There are 4 categories:

• T1 means that the cancer is 1/2 inch or less
• T2 means that the cancer is between 1/2 and 2 inches
• T3 means that the cancer is more than 2 inches
• T4 means that the cancer has grown into adjacent 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 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 tumor (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 Clinical team, namely, multidisciplinary team (MDT) discusses the best treatment and, side effects and care . The treatment depends on:

• where the MCC started and its size
• whether it has spread
• patient's general health

Surgery

Surgery is the main treatment for MCC. The surgeon removes all the cancer cells and a small amount of healthy tissue around it (a healthy margin). The Biopsy to the laboratory and a a Pathologist looks at it under a microscope.

The pathologist makes sure that there is a margin of healthy tissue around the cancer.

The 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.

Radiotherapy uses high energy x-rays to kill cancer cells. One may 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.

One can also have radiotherapy on its own if surgery is not an option.

Radiotherapy is done for 5 days a week for a period of 5 weeks. 

Treatment for cancer that has spread

Treatment for MCC that has spread to other parts of the body will not get rid of the cancer but it can control the symptoms and help one feel better. 

Immunotherapy

Immunotherapy uses the immune system to fight cancer. It works by helping the immune system to recognise and attack cancer cells. 

One have a type of immunotherapy called avelumab (Bavencio). as a drip(IV) into the bloodstream every 2 weeks. IV is done for as long as necessary, provided that side effects are manageable.

Chemotherapy

Chemotherapy uses cytotoxic drugs to kill cancer cells. For MCC, there is usually have a combination of chemotherapy drugs such as:

• carboplatin or cisplatin
• etoposide
• cyclophosphamide
• vincristine
• doxorubicin
• fluorouracil (5FU)

Because Merkel Cell Carcinoma can be aggressive, it's important to seek care early. The good news is that MCC is curable, especially if it is found early.

Author

Paddy Kalish OD, JD and B.Arch