Basal-cell carcinoma
In the United States approximately 3 out of 10 caucasians develop a basal-cell carcinoma during their lifetime. This tumor accounts for approximately 70% of non-melanoma skin cancers. In 80 percent of all cases, basal-cell carcinoma affects the skin of head and neck. Furthermore, there appears to be an increase in the incidence of basal-cell cancer of the trunk in recent years.
Merkel-cell carcinoma
About 80% of Merkel-cell carcinomas are caused by MCV. The virus is clonally integrated into the cancerous Merkel cells. In addition, the virus has a particular mutation only when found in cancer cells, but not when it is detected in healthy skin cells. Direct evidence for this oncogenetic mechanism comes from research showing that inhibition of production of MCV proteins causes MCV-infected Merkel carcinoma cells to die but has no effect on malignant Merkel cells that are not infected with this virus. MCV-uninfected tumors, which account for about 20% of Merkel-cell carcinomas, appear to have a separate and as-yet unknown cause. Those tend to have extremely high genome mutation rates, due to ultraviolet light exposure, whereas MCV-infected Merkel cell carcinomas have low rates of genome mutation.