Cancer is a condition characterized by the uncontrolled growth and division of abnormal cells in the body. These cells, often referred to as malignant cells, differ from normal, healthy cells in several critical ways. Unlike normal cells that grow, divide, and die in a regulated manner, cancer cells continue to grow uncontrollably, invade surrounding tissues, and can even spread to other parts of the body through the blood and lymphatic systems—a process known as metastasis.

Cancerous cells develop due to genetic mutations or changes in the DNA of normal cells. These mutations may occur due to various factors, including exposure to carcinogens (such as tobacco smoke, ultraviolet radiation, or harmful chemicals), inherited genetic predispositions, or random errors during cell division.