About the Kidneys

The kidneys are about the size of your fist. These two bean-shaped organs are shown in the picture below. One is just to the left and the other to the right of the backbone. The lower rib cage protects the kidneys.

The kidneys' main job is to filter the blood and help the body get rid of excess water, salt, and waste products in the form of urine. Urine travels through long, thin tubes (called ureters) to the bladder where it is stored until the person passes the urine, or urinates.

Although we have two kidneys, it is possible to survive with less than even one complete kidney. Some people live without any working kidneys at all. Their blood is filtered by a machine in a process called dialysis.

Kidney Cancer (Renal Cell Carcinoma--RCC)

The most common type of kidney cancer is called renal cell cancer. It accounts for more than 9 out of 10 cases of kidney cancer. While there are other types of kidney tumors, the information that follows refers only to renal cell cancer. The American Cancer Society has more information about other types of kidney tumors available through our toll-free number or on our Web site.

Like all cancers, kidney cancer begins small and grows larger over time. It usually grows as a single mass within the kidney. But a kidney can have more than one tumor. Sometimes tumors are found in both kidneys at the same time. The cancer might be found only after it has become very large. Most of the time it is found before it has spread to other organs through the bloodstream. This is good because like most cancers, kidney cancer can be hard to treat after it has spread (metastasized).

Types of Kidney Cancer

There are several subtypes of RCC, based mainly on how the cancer cells look under a microscope:

Clear Cell RCC

This is the most common form of renal cell carcinoma. About 8 out of 10 people with RCC have this kind of cancer. When seen under a microscope, the cells that make up clear cell RCC look very pale or clear.

Papillary RCC

This is the second most common subtype -- about 10% to 15% of people have this kind. These cancers form little finger-like projections (called papillae) in some, if not most, of the tumor. Some doctors call these cancers chromophilic because the cells take up certain dyes used to prepare the tissue to be looked at under the microscope. The dyes make them look pink.

Chromophobe RCC

This subtype accounts for about 5% of RCCs. The cells of these cancers are also pale, like the clear cells, but are much larger and differ in other ways, too.

Collecting Duct RCC

This subtype is very rare. The major feature is that the cancer cells can form irregular tubes.

Unclassified RCC

In rare cases, renal cell cancers are labeled as "unclassified" because they don't fit into any of the other categories or because more than one type of cell is present.