What Is Cancer and How it Spreads
Cancer is a disease in which certain cells in the body grow uncontrollably and spread to other parts of the body. Cancer can develop almost anywhere in the human body, which contains trillions of cells. Human cells normally grow and multiply (a process known as cell division) to form new cells as the body requires them. Cells die when they become old or damaged, and new cells replace them. When this orderly process fails, abnormal or damaged cells grow and multiply when they should not. These cells can combine to form tumors, which are tissue lumps. Tumors may or may not be cancerous (benign). Cancerous tumors invade nearby tissues and can travel to distant locations in the body to form new tumors (a process called metastasis). Cancerous tumors are also known as malignant tumors. Many cancers form solid tumors, but blood cancers, such as leukemias, do not. Benign tumors do not invade or spread into nearby tissues. When benign tumours are removed, they usually do not recur, whereas canc...