Too much tissue is produced, and tumors begin to form. Tumors can be benign or malignant. Benign tumors are not cancer. They do not spread to other parts of the body and are seldom a threat to life. Often, benign tumors can be removed by surgery, and they are not likely to return.
Malignant tumors are cancer.
They can invade and destroy nearby healthy tissues and organs. Cancer cells also can spread, or metastasize, to other parts of the body and form new tumors. The two most common kinds of skin cancer are basal cell carcinoma and squamous cell carcinoma. Carcinoma is cancer that begins in the cells that cover or line an organ. Basal cell carcinoma, which accounts for more than 90 percent of all skin cancers in the U.S., is a slow-growing cancer that seldom spreads to other parts of the body.