What is Skin Cancer?
Cancer develops when DNA, the molecule found in cells that encodes genetic information, becomes damaged and the body cannot repair the damage. These damaged cells begin to grow and divide uncontrollably. When this occurs in the skin, skin cancer develops. As the damaged cells multiply, they form a tumor. Since skin cancer generally develops in the epidermis, the outermost layers of skin, a tumor is usually clearly visible. This makes most skin cancers detectable in the early stages.
Types of Skin Cancer
Three types of skin cancer account for nearly 100% of all diagnosed cases. Each of these three cancers begins in a different type of cell within the skin, and each cancer is named for the type of cell in which it begins. Skin cancers are divided into one of two classes – nonmelanoma skin cancers and melanoma. Melanoma is the deadliest form of skin cancer.
The different types of skin cancer are:
Basal cell carcinoma (BCC): The most common cancer in humans, BCC develops in more than 1 million people every year in the United States alone. About 80% of all skin cancers are BCC, a cancer that develops in the basal cells – skin cells located in the lowest layer of the epidermis. BCC can take several forms. It can appear as a shiny translucent or pearly nodule, a sore that continuously heals and then re-opens, a pink slightly elevated growth, reddish irritated patches of skin, or a waxy scar. Most BCCs appear on skin with a history of exposure to the sun, such as the face, ears, scalp, and upper trunk. These tumors tend to grow slowly and can take years to reach ½ inch in size. While these tumors very rarely metastasize (cancer spreads to other parts of the body), dermatologists encourage early diagnosis and treatment to prevent extensive damage to surrounding tissue.
Squamous cell carcinoma (SCC): About 16% of diagnosed skin cancers are SCC. This cancer begins in the squamous cells, which are found in the upper layer of the epidermis. About 200,000 cases are diagnosed ever year. SCC tends to develop in fair-skinned middle-aged and elderly people who have had long-term sun exposure. It most often appears as a crusted or scaly area of skin with a red inflamed base that resembles a growing tumor, non-healing ulcer, or crusted-over patch of skin. While most commonly found on sun-exposed areas of the body, it can develop anywhere, including the inside of the mouth and the genitalia. SCC may arise from actinic keratoses, which are dry, scaly lesions that may be skin-colored, reddish-brown or yellowish-black. SCC requires early treatment to prevent metastasis (spreading).
Melanoma: Accounting for about 4% of all diagnosed skin cancers, melanoma begins in the melanocytes, cells within the epidermis that give skin its color. Melanoma has been coined “the most lethal form of skin cancer” because it can rapidly spread to the lymph system and internal organs. In the United States alone, approximately one person dies from melanoma every hour. Older Caucasian men have the highest mortality rate. Dermatologists believe this is due to the fact that they are less likely to heed the early warning signs. With early detection and proper treatment, the cure rate for melanoma is about 95%. Once its spreads, the prognosis is poor. Melanoma most often develops in a pre-existing mole or looks like a new mole, which is why it is important for people to know what their moles look like and be able to detect changes to existing moles and spot new moles.
Other nonmelanoma skin cancers: All other skin cancers combined account for less than 1% of diagnosed cases. These are classified as nonmelanoma skin cancers and include Merkel cell carcinoma, dermatofibromasarcoma protuberans, Paget’s disease and cutaneous T-cell lymphoma.