WebMD defines basal cell carcinoma as a slow-growing skin cancer caused by intense, long-term exposure to the sun. It is the least risky type of skin cancer.
WebMD reports that ultraviolet rays from the sun or from a tanning bed are the primary cause of basal cell carcinoma. Tumors vary widely in appearance and include small shiny bumps, patches of red, slightly scaly skin and waxy, hard growths. The bumps range in color and are fragile, bleeding easily. People with fair skin are more likely to contract basal cell carcinoma. Spreading of this cancer to other areas of the body is unlikely, but it can affect nearby tissue and bones.