Merkel cell carcinoma, often referred to as ‘MCC’, is a rare and highly aggressive skin cancer, which, in most cases, is caused by the Merkel cell polyomavirus (MCV) discovered in 2008. Merkel cell carcinoma, also called neuroendocrine carcinoma of the skin or trabecular cancer, is a very rare type of skin cancer that forms when Merkel cells grow out of control. It tends to grow fast and to spread quickly to other parts of the body. This cancer is considered to be a form of neuroendocrine tumor. Merkel cell carcinoma most often develops in older people and it usually appears as a flesh-colored or bluish-red nodule on the sun-exposed face, head and neck.



The first sign of Merkel cell carcinoma is usually a fast-growing, firm, painless nodule tumor on the skin. Merkel cell cancers tend to invade locally, infiltrating the underlying subcutaneous fat, fascia and muscle and typically metastasize early in their natural history, most often to the regional lymph nodes. MCC's also spread aggressively through the blood vessels, particularly to liver, lung, brain and bone.

The nodule may be skin colored or may appear in shades of red, blue or purple. The nodules typically vary in size from 0.5 cm to more than 5 cm in diameter and usually enlarge rapidly. Most Merkel cell carcinomas appear on the face, head or neck, but they can develop anywhere on the body, even on areas not exposed to sunlight.



It is not clear what causes Merkel cell carcinoma. A newly discovered virus called Merkel cell polyomavirus (MCV) likely contributes to the development of the majority of MCC. Approximately 80% of MCC have this virus integrated in a monoclonal pattern, indicating that the infection was present in a precursor cell before it became cancerous. At least 20% of MCC tumors are not infected with MCV, suggesting that MCC may have other causes as well.


Risk Factors

Factors that may increase the risk of Merkel cell carcinoma include:

  • Excessive exposure to natural or artificial sunlight;
  • A weakened immune system;
  • History of other skin cancers;
  • Older age;
  • Light skin color.



Even with treatment, Merkel cell carcinoma commonly metastasizes beyond the skin. It tends to travel first to nearby lymph nodes. Later it may spread to the brain, bones, liver or lungs, where it can interfere with the functioning of these organs. Cancer that has metastasized is more difficult to treat and can be fatal.



While exposure to sunlight is not proved to cause Merkel cell carcinoma, it is considered the biggest risk factor for this cancer. Reducing the sun exposure may reduce the risk of skin cancer. Hence, a person should try to:

  • Avoid the sun during peak hours;
  • Shield the skin and eyes with a wide-brimmed hat, tightly woven clothing and sunglasses with UV protection;
  • Apply sunscreen liberally and often;
  • Watch for changes on the skin (such as: moles, freckles or bumps that are changing in size, shape or color).