Renal cell carcinoma is the most common type of cancer of the kidneys. This type of cancer usually starts in the renal tubules, which are tiny tubes in the kidneys. Renal cell carcinoma will often remain in the kidneys. But it can spread outside of the kidneys to other parts of the body, including the lungs, brain, and bones. Another form of kidney cancer is clear cell renal cell carcinoma. This is sometimes called conventional renal cell carcinoma. This is the most common kind of kidney cancer. Clear cell renal carcinoma is named this because of how the tutor appears under a microscope. The cells in the tumor appear clear and look like bubbles. In adults, clear cell renal carcinoma makes up about 80% of the cases. This type of cancer is far more common in adults than in children. Renal cell carcinoma will make up about 2% to 6% of kidney cancer in children and young adults.