Merkel cell tumours are rare. They are a type of cancer that arises from Merkel cells. A Merkel cell tumour usually appears as a pink, purple or red nodule on the skin. They most often occur in people over the age of 60 and may grow quite rapidly. About half of these tumours occur on the head and neck with the other half occurring on the hands and feet. This distribution makes it likely that exposure to the sun is one of the factors involved in the development of Merkel cell tumours.

Merkel cells are found in the deep layers of the skin. The function of these cells is not fully understood, but they are found in large numbers close to the nerve endings in the skin. This has led to the suggestion that they are a type of receptor which, when touched, produces hormone-like substances which trigger nerve impulses. Cells that do this are part of the neuroendocrine system, so Merkel cell tumours may also be called primary neuroendocrine carcinomas of the skin, or primary small cell carcinomas of the skin.

The usual treatment for these tumours is surgical removal. The surgeon will aim to remove both the whole tumour and an area of healthy tissue surrounding it. Unfortunately,  the likelihood of the cancer coming back after surgery is quite high. Because of this, radiotherapy is often given as well to improve the chance of cure.

About one third of people with Merkel cell tumours will find the cancer comes back into their lymph glands near to the original tumour. Sometimes the affected lymph glands can be removed by an operation. Sadly, more than half of Merkel cell patients will have problems with the cancer spreading to other parts of their bodies. Chemotherapy has been used in this situation, but because this type of tumour is so rare, it is not possible to say how effective this treatment is.