A kidney tumor is an abnormal mass that develops in a kidney. The kidney is a bean-shaped organ that functions as part of a person's urinary system. It helps to filter waste and extra fluids from the bloodstream, creating urine, which moves to the bladder and out of the body. People are born with two kidneys.
Kidney tumors form when cells overgrow within a kidney. Usually, older cells die and are replaced by new cells. When this process goes awry, the old cells don't die off, and new cells grow when they are not needed, creating a tumor. When a tumor is benign, it is not cancerous and it does not spread to other body parts. However, tumors can sometimes impair organ function, so they may be removed surgically.
Much more serious is a malignant kidney tumor, which is cancerous and can spread to other areas in a person's body. This is potentially life threatening. Renal cell carcinoma, transitional cell carcinoma, and Wilms' tumor are the most frequently diagnosed cancerous kidney tumors. In adults, renal cell carcinoma develops most frequently. Children are more likely to develop Wilms' tumor cancer.
When a person has renal cell carcinoma, kidney tumors develop in the cells of the kidney's filtering units, which are called nephrons. Often, cancerous cells in this area grow as one mass in one kidney. However, it is possible for more than one kidney tumor to develop on just one kidney, and both kidneys can be affected by tumors at the same time.
Transitional cell carcinoma develops in the lining of the renal pelvis, which is the part of the organ responsible for collecting and draining liquid waste. Sometimes these tumors also form in the ureters, which are narrow tubes that lead to the bladder. In some cases, they even develop in the bladder itself.
Wilms' tumors form in the kidneys and can spread to lymph nodes that are near the kidneys. They may also spread to the liver and lungs. Sadly, this type of kidney tumor typically affects children who are less than five years old.
Though anyone can develop renal cell carcinoma, risk increases with age, and they are most common in those who are 60 and above. Men are more at risk than women, and smoking and obesity are also risk factors. Those who are exposed to asbestos, cadmium, and tichlorothylene may be more at risk, as are those who have been treated for kidney failure in the past. For reasons that are not fully understood, those with high blood pressure are also more at risk.
Smoking is also a risk factor for developing transitional cell carcinoma. A person is also more at risk for developing this type of kidney tumor when he works with carcinogenic chemicals in the workplace. A medication called phenacetin, which is no longer on the market in the United States, has been linked to this type of tumor as well.