Merkel cell carcinoma

Cancer is caused by changes (mutations) in the DNA inside of cells. These mutations cause the cells to grow and divide into new cells, when they should not. The mutations that cause MCC are not inherited from a parent, but occur by chance during a person's lifetime (they are acquired, or somatic mutations). In many cases, it is not known what directly causes these mutations to occur. However, several factors are thought to increase the risk for mutations to occur - such as exposure to sunlight.

Merkel cell polyomavirus is frequently involved in the development of MCC and is present in about 80% of MCC tumors tested. While the majority of people have been exposed to this virus by adulthood, it appears that the virus does not cause any symptoms except in the very rare situations in which it leads to MCC.

Other risk factors that have been associated with MCC include:

• being older than age 50
• having fair skin
• having a history of extensive sun exposure
• having chronic immune suppression (e.g. organ transplantation or HIV)

Having one or more risk factors does not mean that a person will develop MCC. Most people with risk factors will not develop MCC.

MCC does not seem to run in families. While DNA changes (mutations) found in the cells of MCC tumors can lead to MCC, these types of mutations are not inherited from a person's parents. They are referred to as somatic mutations and occur during a person's lifetime, often as random events.

Treatment for Merkel cell carcinoma typically begins with surgery to remove the cancer. The first standard surgical procedure is a wide local excision, in which the cancer and some surrounding healthy tissue are removed. A newer surgical technique, known as Mohs surgery, has been shown to be as effective as wide local excision in treating Merkel cell carcinoma. Both techniques are endorsed by the National Comprehensive Cancer Network as acceptable surgical treatments.

Merkel cell carcinoma (MCC) is considered an aggressive type of cancer, even more aggressive than melanoma. This means that it rapidly grows and spreads to nearby tissues or distant parts of the body (metastasizes). Estimates of the time it takes for MCC to progress from an early to advanced stage, or to cause death, is unknown because MCC is rare, the diagnosis can be difficult to make, and treatments vary. One study of 195 patients did mention that approximately two-thirds of Merkel cell carcinomas expanded in size rapidly over the course of three months.

Many factors are thought to influence the progression of MCC, including the size and location of the tumor, whether or not the tumor has spread to lymph nodes or distant sites in the body, whether the cancer regrows after treatment (a recurrence), and what types of treatments are used. Unfortunately, approximately one third of individuals affected with MCC are diagnosed when the cancer is already advanced, meaning the cancer has metastasized to the lymph nodes or farther. The advanced state at diagnosis is due to the fact that MCC can be difficult to diagnose because it appears similar to benign skin findings, is often painless, and grows so rapidly.

Successful treatment of Merkel cell carcinoma depends on the removal of all cancerous cells, including the main cancer and any cancerous cells that may have spread to nearby lymph nodes or to more distant parts of the body. To increase the chance of removing all cancerous cells, a process known as staging is used to determine the extent of the cancer in the body. A sentinel lymph node biopsy, in which the lymph nodes are first "mapped" using a radioactive material or blue dye in an attempt to identify the lymph node most likely to contain cancerous cells, may be an important step in staging Merkel cell carcinomas, particularly those that occur in the head and neck. This lymph node, known as the sentinel lymph node, is then surgically removed and examined for the presence of cancer. In Merkel cell carcinoma, radioactive material has been shown to be more effective than blue dye alone for identifying sentinel lymph nodes.

Individuals with Merkel cell carcinoma (MCC) are not contagious. Although in some cases cancer can be caused by infectious agents such as specific bacteria, parasites, and viruses (pathogens), cancer is generally not considered a transmissible disease.

Merkel cell polyomavirus, which has been found to be present in 80% of MCC tumors, is considered to be an organism that normally inhabits the human body; asymptomatic infection with the virus is common. It is typically acquired in early childhood. MCC is a rare cancer, and the overwhelming majority of individuals who are infected with the virus will never develop MCC. The virus itself is transmissible (although the mode of transmission is not well understood), but MCC cannot be passed from one individual to another.

SkinCancerNet is a comprehensive online skin cancer information resource developed by the American Academy of Dermatology. Click on the link to view information on Merkel cell carcinoma.