What is Cancer?
Author: Gesche Tallen, MD, PhD, erstellt 2003/12/11, Editor: Dipl.-Biol. Maria Yiallouros, Reviewer: Prof. Dr. med. Dr. h. c. Günter Henze, Last modification: 2010/04/17
Cancer is a collection of diseases that have in common uncontrolled cell growth and the ability to invade the healthy parts of the body. Normal cells have an inner clock that regulates its different phases of life. It tells them, together with signals from other cells, when to divide, if it is time to grow, how to mature and when to age and to die. Cancer cells are called immortal, because most of them have lost this inner clock determining their life span.
Childhood cancer in a person younger than 20 years is rare in Europe. It accounts for only 1% of all childhood diseases.
Theoretically, every cell in the human body can turn into a cancer cell. Therefore, there are many different types of cancer in children, teenagers and also in adults. Dependent on the cell of origin as well as on which and how many organs of the body are being affected by the disease, cancer can cause different symptoms. Also, the different types of cancer require different treatments and have different outcomes.
Cancer can occur as a leukaemia or as a lymphoma, for example, thereby affecting the complete blood forming or lymphatic system. The ability to affect many organs of the human body makes cancer a, professionally speaking, systemic disease. Cancer cells often build clusters (solid tumours) in an organ and are named based on the tissue of origin. For example, if having arised from nerve cells, connective or supportive tissue, such as cartilage, bone or muscle, a tumour is called sarkoma. Carcinomas develop from changes in cells of glands or organ walls. Carcinomas a rather rare in the young. If a tumour originates from very primitive cells (embryonal cells or blasts), which is very typical for tumours in children and teenagers, their corresponding name usually ends with -"blastoma". Due to the pimitivity and immaturity of their cells, it is often difficult to determine the cell or tissue type of origin in a blastoma.
Cancer cells are typically out of control and divide without a limit. And while they are dividing, they often copy their malignant characteristics. Most of the time, they do not function properly. Instead, they can spread wihtin the region where they arose (locally) and travel to sites of the body that are far away from their origin (metastasis). It is assumed that, although often not detectable by routine tests, every cancer has already produced numerous tiny (micro-) metastases already at initial diagnosis. The ability to spread makes cancer a malignant disease, meaning that, if not treated appropriately, it can progress and lead to death.
Therefore, treating the visible malignant tumour only is not enough. Instead, even the tiniest spread (micrometastases) has to be considered and treated from the beginning of therapy. This approach is called systemic treatment. In fact, no matter which cell type the cancer has arisen from, the disease almost always affects the whole human organism.
Its numerous aggressive properties, that can harm the whole body, make cancer a fatal malignant disease.
