The bottom one third of the screen is occupied by normal kidney and the upper 2/3 is occupied by the renal cell carcinoma. (Because the tumor is similar in appearance to that of the adrenal gland the name hypernephroma was at one time popular) Other synonyms for renal cell carcinoma are clear cell tumor, renal adenocarcinoma, and Grawitz's tumor. A normal adult kidney is typically 12 cm x 5 cm x 3 cm. Renal cell carcinoma accounts for 1 to 3% of all visceral cancers and in adults accounts for 85 to 90% of all renal cancers. Grossly, these tumors are between 3 and15 cm in diameter and are yellow. They are highly invasive and often invade the renal veins. It is not unusual for the tumor to extend into the inferior vena cava. Microscopically, two variants predominate: 1) the clear cell-type (commomest) in which the cells are clear due to the accumulation of glycogen and lipid, and 2) the granular type in which the cells are granular due to the large number of mitochondria.