What is kidney cancer?

Kidney cancer starts in the cells of the kidney. A cancerous (malignant) tumour is a group of cancer cells that can grow into nearby tissue and destroy it. The tumour can also spread (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 (pee) 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 kidneys sometimes change and no longer grow or behave normally. These changes may lead to non-cancerous (benign) conditions such as cysts. They can also lead to non-cancerous tumours such as papillary renal adenoma.

But in some cases, changes to kidney cells can cause kidney cancer. Most often, kidney cancer starts in the cells that line the tubules. This type of cancer is called classic renal cell carcinoma, or clear cell carcinoma. Cancers that start from other cells in the kidney are called non-clear cell carcinoma.

Rare types of kidney cancer can also develop. These include renal sarcoma and primary renal lymphoma.