Merkel cell carcinoma

Cancer is caused by changes (mutations) in the DNA inside of cells.^[1] 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.[7331]^[2]

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.^[2]

Other risk factors that have been associated with MCC include:^[3][2]

• 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.^[3]

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.^[4]

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.^[5] 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.