Cancer is the uncontrolled growth of cells.
The cancerous cell mass is called a tumor or neoplasm. Cancer cells grow more rapidly than normal, healthy cells. Of the cancerous cells, benign tumors tend to grow less quickly, remain localized to a distinct mass, and can be cured by surgical removal. Causes Most tumors result from unknown causes. Diagnosis and Testing Health history, clinical signs, physical exam, and X-rays may identify the presence of a tumor, but definitive diagnosis of cancer requires identification of the tumor cells under a microscope.