Introduction to Skin Cancer
Melanoma is a form of skin cancer that occurs in the melanocytes, which are cells in the outer layer of the skin (the epidermis). Melanocytes produce the skin coloring or pigment known as melanin, which gives skin its tan or brown color and helps protect the deeper layers of the skin from the harmful effects of the sun. Melanoma develops when melanocytes undergo malignant transformation, become abnormal, grow uncontrollably and aggressively invade surrounding tissues. Melanoma may affect only the skin, or it may spread through the blood or lymph system to other organs and bones.
Melanoma is the most serious form of skin cancer. Melanoma may be cured if caught and treated early, but, if left untreated, the majority of melanomas eventually spread to other parts of the body. Early detection and surgery to remove the melanoma are successful in curing most cases of melanoma; however, it is rarely curable in its later stages.
In the United States, melanoma accounts for approximately 4% of all newly diagnosed cancers annually. The American Cancer Society estimates that in 2004, approximately 55,100 new melanomas will be diagnosed and about 7,910 deaths due to melanoma will occur in the United States.
Internationally, the incidence of melanoma varies greatly, with the highest incidence occurring in Australia, the United States, Norway, Switzerland, Sweden, Denmark and Israel, and the lowest incidence in Japan, the Philippines, China and India.
Melanoma commonly afflicts the young and middle aged; however, people of all ages are at risk. It is the most common cancer in young adults aged 20-30 and is the leading cause of cancer death for women aged 25-30. Melanoma is significantly more prevalent among white populations than in blacks and Asians; the incidence of melanoma in blacks is approximately 1/20 than that of whites.
There has been a dramatic increase in melanoma incidence over the last century. The lifetime risk of developing melanoma in 1935 was only 1 per 1500 Americans, and the lifetime risk for melanoma in 2004 was 1 in 71 Americans. The lifetime risk is estimated to rise to 1 in 50 Americans by 2010. Fortunately, due to prevention and early detection practices, melanoma mortality rates have not increased as sharply and have remained stable or decreased since the 1990s.