Cancer is the name for a group of related diseases, and they all have in common that part of the cells in the body begins to uncontrollably divide without stopping and spread into the surrounding tissue< /span>. Cancer can appear in any part of the body. Under normal circumstances, cells grow and divide to make new cells when the body needs them, and when cells become old or damaged they die and new cells take their place. In cancer, however, this orderly process is disrupted. Old and damaged cells survive even though they should die, and new cells are created even though they are not needed. Due to uncontrolled division, there is an accumulation of cells which is manifested as the formation of tumor. Many tumors create such solid accumulations (tissue mass), while this is not the case with malignant blood tumors such as leukemia. Cancer is a malignant tumor, which means that cancer cells can spread into or invade surrounding tissue. Also, with the growth of the tumor mass, some cells can be "torn off" and travel to distant parts of the body via the blood or lymphatic system and form new tumor masses (metastases) far from the site of the primary tumor. Unlike malignant tumors, benign tumors do not spread into or invade the surrounding tissue. Sometimes they can be very large, but if they are removed, they usually do not recur, which is not uncommon with malignant tumors. However, not all benign tumors are harmless; benign brain tumors can be life-threatening due to mechanical pressure on the surrounding tissue.
Figure 1. Representation of breast cancer cells. Such cells divide uncontrollably and begin to invade the surrounding tissue.
Cancer cells differ from normal cells in several ways, which allows them to grow without control and invade the surrounding tissue. One of the important differences is that normal cells are highly specialized and mature into cells with specific functions, while cancer cells do not. It is precisely because of this immaturity that cancer cells continue to divide without stopping. Also, cancer cells are able to ignore signals that tell the cell to stop dividing or to start the process of programmed cell death (apoptosis), by which the body gets rid of unnecessary cells or those that are so damaged that they cannot be fix. In addition to being changed themselves, cancer cells can also affect the surrounding healthy cells and blood vessels (the so-called microenvironment) and "adapt" for personal gain. One such example is stimulating the creation of new blood vessels that enable the tumor to be supplied with the oxygen and nutrients it needs to grow. Namely, tumor tissue consumes large amounts of nutrients and they need a constant supply of them, otherwise necrosis/disintegration of the tumor occurs. These blood vessels also serve to drain tumor waste products. In view of the above, a whole series of targeted drugs have been developed over time that prevent the formation of new blood vessels and thus have an indirect anti-tumor effect. Although the immune system regularly removes damaged and abnormal cells in the body, cancer cells are very successful at evading the immune response. They achieve this by various mechanisms, which hide cancer cells from recognition and at the same time lead to suppression of the immune system.
Additional points of interest
We often think that cancer is a disease of the new age that "our old people" was unknown, but in fact it is not so. The oldest written record of cancer as a disease dates back to 1600 BC. It is an Egyptian papyrus that describes cases of breast cancer.
Continue reading: How and why does cancer occur?
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