The number of cases of MCC that are diagnosed yearly has been steadily increasing in the United States. This is likely due to the aging population, since 95% of all MCC’s are diagnosed in patients over the age of 50. The incidence of this cancer in 2001 was 0.44 per 100,000 people for approximately 1400 cases per year. At the time of diagnosis, approximately 25% of patients will already have spread to the lymph nodes and 5% will have spread to distant sites in the body.
As with other cancers, there are certain risk factors that are associated with the development of MCC.
Ultraviolet light exposure: There are several observations that support an association between ultraviolet radiation and the development of MCC. First, most of these lesions are found on sun exposed areas such as the head and neck. Second, regional differences in MCC incidence are associated with differences in the ultraviolet-B index. Finally, patients exposed to ultraviolet-A rays for treatment of psoriasis have an increased incidence of MCC.
Immunosuppression: There appears to be an association between MCC and immunosuppression. The incidence of MCC is increased in patients who are on immunosuppression, such as transplant patients, or patients with immune deficiency syndromes.
Age: As people get older, the risk of developing MCC increases.