Melanoma is a form of cancer that begins in melanocytes, specialized cells in the skin that produce the brown pigment known as melanin. These are the cells that darken when exposed to the sun, a protective response to protect the deeper layers of the skin from the harmful effects of the sun.
Melanoma cancer accounts for approximately 5% of all skin cancers. The American Cancer Society, one of the country’s leading resources for cancer information, estimates that approximately 70,230 new cases of melanoma will be diagnosed in 2011, and the incidence rate is increasing. The lifetime risk of developing melanoma is highest in Caucasians (1 in 50), while approximately 1 in 1,000 blacks and 1 in 200 Hispanics will develop this disease. While the risk of melanoma cancer increases with age, it can occur in younger people, and is one of the more common cancers in young adults.
Melanoma is highly curable if caught early, but is much more likely than other forms of skin cancer to spread if left untreated. The most common type of melanoma cancer is cutaneous melanomas, which develop on the skin, particularly in areas exposed to the sun, although they can develop anywhere. In men, the most common site is the chest or back, while in women, the legs are affected most frequently. However, melanomas are also commonly found on the neck or face.
While having dark skin lowers the risk of developing melanoma in these more common locations, individuals with darker skin are still at risk for the development of melanoma on the palms of the hands, soles of the feet or under the fingernails. Clusters of melanocytes can also form a benign (noncancerous) growth, or mole (also known as a nevus). While most moles are harmless, some types may raise your risk of developing melanoma cancer.
More rarely, melanomas can develop in the eyes, called ocular melanoma, or mouth or vagina, called mucosal melanoma.
Cholangiocarcinoma (Bile Duct Cancer) occurs in the small, tube-like bile ducts within the liver that carry bile to the gallbladder. Cholangiocarcinomas account for 10-20 percent of all liver cancers. Intrahepatic bile duct cancer begins in ducts within the liver. Extrahepatic bile duct cancer develops in ducts outside of the liver.
Angiosarcoma, also called hemangiocarcinoma, accounts for about 1 percent of all liver cancers. Angiosarcomas begin in the blood vessels of the liver and grow quickly. They are typically diagnosed at an advanced stage.