from wikipedia

Symptoms of cancer metastasis depend on the location of the tumor.Cancer /ˈkænsər/ ( listen), known medically as a malignant neoplasm, is a term for a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the body through the lymphatic system or bloodstream. Not all tumors are cancerous. Benign tumors do not grow uncontrollably, do not invade neighbouring tissues, and do not spread throughout the body.

Healthy cells control their own growth and will destroy themselves if they become unhealthy. Cell division is a complex process that is normally tightly regulated. Cancer occurs when problems in the genes of a cell prevent these controls from functioning properly. These problems may come from damage to the gene or may be inherited, and can be caused by various sources inside or outside of the cell. Faults in two types of genes are especially important: oncogenes, which drive the growth of cancer cells, and tumor suppressor genes, which prevent cancer from developing.

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