Cancer

What is cancer?

The body's basic unit—the cell—has a life cycle during which it grows, divides, and dies. Cells divide to produce more cells only when additional cells are needed by the body. This orderly life cycle is what keeps the body healthy. During childhood and adolescence, normal cells divide more rapidly until a person reaches adulthood. After that, cells in most parts of the body divide only to replace old or dying cells and to repair injured organs or tissues. However, cancer occurs when abnormal cells divide without control or order. Rather than dying, cancer cells outlive normal cells and continue to produce new, abnormal cells.

Cancer cells develop as a result of damage to deoxyribonucleic acid, or DNA. Present in every cell of the body, DNA directs the activities of the cell. In most cases, when DNA becomes damaged, the body is able to repair it. In cancer cells, however, damaged DNA is not repaired. The cell takes on an abnormal life cycle and continues to grow and divide in an out-of-control fashion. Cells continue to divide when new cells are not needed, resulting in a mass of extra tissue. Such masses—known as tumors—may be benign or malignant.

Benign tumors are not cancer. Non life-threatening, these can be removed, and generally, they do not recur. Cells from benign growths do not metastasize (spread) to other parts of the body. Polyps, and cysts are examples of benign growths.

Malignant tumors, on the other hand, are cancerous. Such growths can invade and damage nearby tissues and organs through a process called metastasis. Cancer cells can also break away from a malignant tumor and enter the body's lymphatic system or bloodstream, replacing normal tissue. This is how cancer can spread (metastasize) to other parts of the body such as the lymph nodes, rectum, bladder, lungs, and bones of the spine.