Cancer starts when the structure of the DNA (deoxyribonucleic acid) alters - a genetic mutation. DNA provides the cells with a basic set of instructions, much like a computer program for life. The instructions tell cells when to grow, reproduce, and die, among other things. When there is a genetic mutation cells grow in an uncontrollable manner, eventually producing a lump (tumor).
If the cancer is left untreated it grows and eventually spreads to other parts of the body, usually through the lymphatic system - a series of nodes (glands) that exist throughout the body. The lymph glands produce many of the cells of our immune system. As soon as the cancer reaches the lymphatic system it can spread anywhere in the body and invade bones, blood and organs. The cancer cells continue reproducing uncontrollably, gradually occupying more and more space.
Our kidneys are part of our urinary system which gets rid of waste and excess fluid and electrolytes from the blood. The kidneys also control the production of red blood cells and regulate your blood pressure.
There are over 1 million nephrons in each kidney. Nephrons are the tiny filtering units in the kidneys - they filter out waste products as well as minerals and water the body needs expel. The liquid waste is called urine. Urine flows through the ureters; two narrow tubes that connect the kidneys to the bladder. Urine is stored in the bladder. When we urinate (pee) urine travels down another tube, called the urethra, and out of the body.
Acquired gene mutations
Most DNA mutations related to kidney cancer, however, occur during a person's life rather than having been inherited. These acquired changes in oncogenes and/or tumor suppressor genes may result from factors such as exposure to cancer-causing chemicals (like those found in tobacco smoke), but in many cases what causes these changes is not known.
About 3 out of 4 people with sporadic (non-inherited) clear cell renal cancer have changes in the VHL gene that cause it not to function properly. These changes were acquired during life rather than being inherited. Other gene changes may also cause renal cell carcinomas. Researchers continue to look for these changes.
Progress has been made in understanding how tobacco increases the risk for developing renal cell carcinoma. Your lungs absorb many of the cancer-causing chemicals in tobacco smoke into the bloodstream. Because your kidneys filter this blood, many of these chemicals become highly concentrated in the kidneys. Several of these chemicals are known to damage kidney cell DNA in ways that can cause the cells to become cancerous.
Obesity, another risk factor for this cancer, alters the balance of some of the body's hormones. Researchers are now learning how certain hormones help control the growth (both normal and abnormal) of many different tissues in the body, including the kidneys.
What is known about the gene changes that lead to kidney cancer is being used to help develop new treatments for this disease. For example, researchers now know that the VHL gene normally stops cells from making a substance called vascular endothelial growth factor (VEGF). Tumors need new blood vessels to survive and grow and VEGF causes new blood vessels to form. Newer drugs that target VEGF are now being used to treat kidney cancer.
Inherited gene mutations
Certain inherited DNA changes can lead to conditions running in some families that increase the risk of kidney cancer. These syndromes, which cause a small portion of all kidney cancers. For example, VHL, the gene that causes von Hippel-Lindau (VHL) disease, is a tumor suppressor gene. It normally helps keep cells from growing out of control. Mutations (changes) in this gene can be inherited from parents, causing von Hippel-Lindau disease. When the VHL gene is mutated, it is no longer able to suppress abnormal growth, and kidney cancer is more likely to develop. The genes linked to hereditary leiomyoma and renal cell carcinoma (the FH gene), Birt-Hogg-Dube syndrome (the FLCN gene), and familial renal cancer (SDHB and SDHD) are also tumor suppressor genes, and inherited changes in these genes also lead to an increased risk of kidney cancer.
People with hereditary papillary renal cell carcinoma have inherited changes in the MET oncogene that cause it to be "turned on" all the time. This can lead to uncontrolled cell growth and makes the person more likely to develop papillary renal cell cancer.