Merkel cell carcinoma

A crowd of people sunbathing at a beach

What is Merkel cell carcinoma?

Merkel cell carcinoma (MCC) is a very rare type of skin cancer that forms when malignant (cancerous) Merkel cells produce tumour on the skin. It is also known as neuroendocrine carcinoma or trabecular cancer.

This disease most commonly originates in skin that has been exposed to the sun, particularly the face, neck, arms and legs. Merkel cells are found in the upper layer of the skin, very close to the nerve endings that receive the sensation of touch. It tends to grow fast and metastasise (meaning cancer cells spread to other parts of the body) at an early stage. It usually spreads to nearby lymph nodes first, and then spreads to distant lymph nodes, skin on other parts of the body or other organs such as the lungs, brain and bones.

Prognosis

The prognosis, as well as treatment plan, depends on the stage of the cancer at the time of diagnosis. Merkel cell carcinoma that has spread to the lymph nodes or other body parts becomes more difficult to treat. In general, patients with Merkel cell carcinoma that hasn’t spread have increased survival rates.

Prognosis also depends on:

  • Where the cancer originated
  • Time of diagnosis: If the cancer was recently diagnosed or if it has come back
  • Patient characteristics such as age and general health.
  • The depth of the tumour in the skin

Symptoms

Merkel cell carcinoma usually appears on the skin as a single lump with the following characteristics:

  • It grows fast
  • It doesn’t hurt
  • It’s firm and dome-shaped or raised
  • It’s red or violet in colour

Medical tests to diagnose Merkel cell carcinoma

Tests and procedures to examine the skin are used to detect and diagnose Merkel cell carcinoma. Some of the tests and procedures that are performed include:

General examination

  • Medical history: An evaluation of symptoms and any past illnesses
  • Physical exam: The skin is checked for abnormal-looking lumps or spots in colour, size, shape, or texture

Biopsy to remove tissue and send it for examination

  • Skin biopsy: Skin cells are removed for a pathologist to look at under a microscope and check for signs of cancer
  • Sentinel lymph node biopsy: To check if MCC has spread to the lymph nodes and entered the lymphatic system

Imaging tests to investigate if MMC has spread throughout the body.

What are the causes?

The exact cause of Merkel cell carcinoma is unknown, but risk factors have been strongly linked to it:

  • Extensive exposure to natural sunlight
  • Exposure to artificial sunlight, such as in tanning beds
  • Having a weakened immune system due to an existing condition, such as chronic lymphocytic leukaemia or HIV
  • Taking medications that make the immune system less active, such as after an organ transplant
  • Having a history of other types of cancer
  • Being over 60 years old, male or white

Can it be prevented?

Since Merkel cell carcinoma appears to be related to exposure to ultraviolet (UV) rays, several key measures must be taken to limit exposure.

  • Minimise sun exposure as much as possible: Find areas in the shade, minimise outdoor activities between 10 am and 4 pm, that is, when the sun's rays are strongest. It’s also preferable to avoid sunbathing and using sunbeds.
  • Wear protective clothing: Wear long-sleeved shirts, long trousers, and wide-brimmed hats if in the sun for extended periods of time.
  • Use of sunscreen: It’s recommended to use sun protection with a factor of at least 30 and a broad spectrum of UVA/UVB protection.

Treatments for Merkel cell carcinoma

Treatment is determined by the stage of the cancer. It usually includes:

  • Surgery: The skin tumour (growth of cancerous Merkel cells) is removed via a surgical excision along with a portion of surrounding normal skin. If MCC has been identified in the lymph nodes in the area of the skin tumour, they are removed too via lymph node dissection. Mohs surgery is one of the available techniques.
  • Immunotherapy: Immunotherapy drugs help your immune system fight off the cells. It’s usually used after the cancer has spread from its original site.
  • Radiotherapy: This uses high energy beams to destroy cancer cells. It’s sometimes used after surgery to destroy any remaining cancer cells after surgical removal.
  • Chemotherapy: This is most often used in cases where MCC has metastasised (spread to lymph nodes or other organs) or for cancer that has returned after treatment.

Which specialist treats it?

Dermatologists are responsible for the study, diagnosis and treatment of all diseases that affect the skin, including Merkel cell carcinoma.

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