Cancer

What is cancer? Cancer is a disease characterized by the presence of malignant tumors in the body. Malignant tumors can spread into surrounding tissues and invade other parts of the body displacing normal tissue and interrupting organ function as it grows. A tumor grows from a single cancer cell. It starts when the cell undergoes transformation, converting a normal cell to a cancer cell. A transformed cell grows abnormally and the immune system usually recognizes it and destroys it. If the cell somehow avoids destruction, it may multiply to form a tumor. A tumor is a mass of abnormally growing cells with otherwise normal tissue. If the abnormal cells remain in their original spot, then a benign tumor has formed. These tumors can be dangerous if they spread to the brain but if they maintain size and location they can be left alone. If needed, they can be completely surgically removed. What you don't want is for the cancer cells to spread through lymph and blood vessels to other parts of the body. This process is called metastasis. Unfortunately, cancer cells are not density-dependent. If they were, they would stop multiplying when they have filled a single layer. Instead they keep dividing, forming a clump of overlapping cells.

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