Kidney cancer is a disease in which cancer cells grow in the kidneys. The kidneys are two bean-shaped organs, located just above the waist, on each side of the spine. Their main function is to filter the blood and produce urine by which the body rids itself of waste products and excess water.
Cancer occurs when cells in the body (in this case kidney cells) divide without control or order. Normally, cells divide in a regulated manner. If cells keep dividing uncontrollably when new cells are not needed, a mass of tissue forms, called a growth or tumor. The term cancer refers to malignant tumors, which can invade nearby tissue and spread to other parts of the body. A benign tumor does not invade or spread.
There are two main types of kidney cancer: Wilms’ tumor , which occurs predominantly in children, and renal cell carcinoma in adults. The cells that line the ureter may also give rise to transitional cell cancer, and the connective tissues of the kidney may produce sarcomas, which are rare.