Kidney cancer is a malignant tumour that starts in the cells of the kidney. Malignant means that it can spread, or metastasize, to other parts of the body.
The kidney is part of the urinary system. The 2 kidneys are on either side of the backbone, deep inside the upper part of the abdomen.
On the top of each kidney is an adrenal gland. The kidneys make urine by filtering water and waste material from the blood. Inside each kidney is a network of millions of small tubes called nephrons. Each nephron is made up of a tubule and a corpuscle. Tubules are tiny tubes that collect the waste materials and chemicals. Corpuscles have a clump of tiny blood vessels that filter the blood.
Cells in the kidney sometimes change and no longer grow or behave normally. These changes may lead to benign conditions such as cysts. They can also lead to benign tumours such as renal adenoma. Benign conditions and tumours are not cancerous. But in some cases, changes to kidney cells can cause cancer.
Most often, kidney cancer starts in cells that line the tubules. This type of cancer is called renal cell carcinoma. There are several different types of renal cell carcinoma.
Rare types of kidney cancer can also develop. These include renal sarcoma and primary renal lymphoma.