There are two main types of primary kidney cancer: renal cortical tumors and transitional cell (urothelial) tumors. These types are different in the way they develop and change over time, as well as in how they should be treated.
Renal Cortical Tumors
Up to 90 percent of kidney tumors are renal cortical tumors. These tumors start in the main part of your kidney, which contains structures called renal tubules.
Your kidneys each hold more than a million nephrons, which filter your blood and produce urine. Each nephron is associated with a renal tubule. Tubules join together to form collecting ducts. These ducts deposit the urine in your renal pelvis.
Cancer that develops in the renal tubules is called a renal cortical tumor. There are several types, and they don’t necessarily affect people in predictable ways. Some types are some are malignant (cancerous). But other types — such as renal cysts, oncocytomas, and angiomyolipomas — are benign (noncancerous).
- Conventional tumors (also called clear cell tumors) account for 60 to 65 percent of kidney tumors.
- Papillary tumors account for 10 to 15 percent of kidney tumors. They can start as one or more tumors in one or both kidneys. There are two types of papillary tumors. Type 1 is more common and usually grows slowly. Type 2 is generally much more aggressive and unpredictable. Papillary tumors have been associated with certain genetically inherited syndromes, such as hereditary papillary renal carcinoma, hereditary leiomyomatosis, and renal cell carcinoma. You may need genetic testing if your doctor suspects that you have one of these syndromes.
- Chromophobe tumors are considered a less aggressive form of kidney cancer, accounting for 5 to 10 percent of kidney tumors. They may reach a very large size before they spread.
- Oncocytoma has almost no risk of spreading or causing death; 5 to 10 percent of kidney tumors are oncocytomas.
- Collecting duct tumors are very rare (less than 1 percent of kidney tumors) and more common in younger adults. They are aggressive and don’t respond to conventional treatment.
- Unclassified tumors look different than other tumors under the microscope and are usually very aggressive. While rare, they do account for 3 to 5 percent of kidney tumors.
Transitional Cell (Urothelial) Tumors
This type of kidney cancer starts in your renal pelvis, where the renal tubules leave urine. We’ll consider such factors as the location and size of a transitional cell tumor in deciding on the best approach for you.