About 90% of cancers of the kidney occur in the renal cells; these cancer are also called renal cell adenocarcinomas. They begin in the cells that line the small tubes of the renal cortex.

There are different types of cancers of the renal cells, though the most common is clear cell cancer. Other, less common cancers include papillary renal cell cancer and chromophobe renal cell cancer, and cancer of the collecting ducts.

Another type of cancer that can affect the kidneys starts in the cells that line the renal pelvis, where the kidney joins up with the ureter. This type, sometimes called transitional cell cancer, behaves and is treated differently from renal-cell cancers.