Melanoma is the most dangerous skin cancer. The cancer comes from an abnormal growth of cells that produce skin pigment (melanocytes). Exposure to the sun or tanning beds increases one's risk of the disorder. Early detection and treatment enables the cancer to be removed before it spreads (metastasizes). Once the tumor has spread to lymph nodes and other organs the cure rate becomes very low. The American Cancer Society recommends professional skin exams every year for people older than 40, and every 3 years for people aged 20 - 40. Besides the skin these tumors can occur in the eyes and rarely in the intestines.