Skin cancer is the abnormal growth of skin cells. It most often develops on skin exposed to the sun, but can also occur on areas that are not ordinarily exposed to sunlight. Skin cancer is generally divided into two stages, local (where the cancer affects only the skin) and metastatic (where cancer has spread beyond the skin).
More than one million new cases of skin cancer will be diagnosed in the United States this year. One in five Americans will develop some form of skin cancer during their lifetime.
The skin consists of three layers including the epidermis, dermis, and the subcutaneous layer. The epidermis is the outermost layer and is very thin. It provides a protective layer of skin cells that sheds continually. Squamous cells lie just below the outer surface. Basal cells, which produce new skin cells, are at the bottom of the epidermis. The epidermis also contains cells called melanocytes, which produce melanin, the pigment that gives skin its normal color and causes moles. When exposed to the sun, these cells produce more melanin that helps protect the deeper layers of skin. The extra melanin is what produces the darker color of tanned skin.
There are three major types of skin cancer, including basal cell carcinoma, squamous cell carcinoma, and melanoma. Basal and squamous cell carcinomas are slow growing and generally highly treatable. If all forms of skin cancer are found early and treated appropriately, they are all nearly 100% curable. It is very important to limit or avoid exposure to ultraviolet (UV) radiation and pay close attention to suspicious changes in the skin.
Other less common types of skin cancer include Kaposi's sarcoma, Merkel cell carcinoma, and sebaceous gland carcinoma.
Basal cell carcinoma: Basal cell carcinoma (BCC) is the most common form of cancer, accounting for nearly 90% of all skin cancers. Basal cells are cells that line the deepest layer of the epidermis. An abnormal growth of cells in this deep layer is known as BCC. Although BCC can usually be diagnosed with a simple biopsy, has a low rate of metastasis, and is fairly easy to treat when detected early, 5-10% of BCCs can be logically aggressive and resistant to treatment. BCC may invade bone and cartilage, and if not treated appropriately and early, it may be very difficult to eliminate.
Squamous cell carcinoma: Squamous cell carcinoma (SCC) is the second most common form of skin cancer, with over 200,000 new cases per year estimated in the United States. Squamous cells are cells that compose most of the epidermis. An abnormal growth of squamous cells is known as a SCC. Most SCCs are not life-threatening when identified early and treated appropriately, but SCC may become more difficult to treat, can cause disfigurement, and a small percentage may spread (metastasize) to other organs resulting in death.
Melanoma: Although melanoma is not the most common of the skin cancers, it causes the most deaths. The American Cancer Society estimates that in 2007, there will be 59,940 new cases of melanoma in the United States. Melanoma is a malignant tumor that originates in melanocytes (produce melanin). The majority of melanomas are black or brown, although some melanomas occasionally stop producing pigment and may be skin tone, pink, red, or purple.
Acral lentiginous melanoma, actinic cheilitis, actinic keratoses, arsenical keratosis, biological therapy, Bowen's Disease, dysplastic nevi, Breslow's thickness, epidermis, familial atypical multiple mole melanoma (FAMMM), immunity, immunotherapy, Kaposi's sarcoma, lentigo maligna, melanin, melanocytes, nodular melanoma, oncogenes, Mohs' surgery, photodynamic therapy, seborrheic keratoses, squamous cells, sunscreen, topical immunotherapy, UV light.