What is Kidney Cancer?

Your kidneys are two fist-sized, bean-shaped organs located in the back of your torso, just above your waist. Your kidneys are responsible for filtering waste and excess water from your blood and turning it into urine. Over 90% of kidney cancers are renal cell carcinomas (RCC), which form in the lining of the tubules (tiny tubes that filter your blood and produce urine). There are several main types of renal cell carcinoma, some of which are described below:

Types of Renal Cell Carcinoma:

• Clear cell: Makes up about 70% to 80% of renal cell carcinomas. Cancer cells appear clear under a microscope.
• Papillary: Makes up about 10% of all renal cell carcinomas. Tumors form finger-like projections called papillae and can develop in one or many locations.
• Chromophobe: Makes up about 5% of all renal cell carcinomas. This is one of the least aggressive forms of kidney cancer.
• Collecting Duct: This is a very rare (less than 1%) form of renal cell carcinoma in which the cells form irregular tubules. It primarily occurs in young adults, is aggressive, and does not respond well to conventional treatments.
• Unclassified: Makes up 3% to 5% of all renal cell carcinomas. These tumors look different than any other subtype and may be a combination of subtypes. Unclassified renal cell carcinomas are usually very aggressive.

About 5% to 10% of kidney cancers are transitional cell carcinomas, which start in the cells lining the renal pelvis. These cells are the same type of cell found in the ureters and bladder. This means transitional cell tumors behave more like bladder tumors than renal cell carcinomas. Renal sarcomas that start in the connective tissues or blood vessels are also a rare type of kidney cancer. This document focuses mainly on renal cell carcinomas, the most common form of kidney cancer.