Renal cell carcinoma (RCC, also known as hypernephroma, Grawitz tumor, renal adenocarcinoma) is a kidney cancer that originates in the lining of the proximal convoluted tubule, a part of the very small tubes in the kidney that transport waste molecules from the blood to the urine. RCC is the most common type of kidney cancer in adults, responsible for approximately 90-95% of cases.