Tumor may affect any region of the kidney. There is a predilection for the upper pole. On cut surface, the tumor may be bright yellow and this feature correlates with high lipid content. A geographic pattern to the cut surface is frequently seen due to ischemia, necrosis, and hemorrhage. Tumor-parenchymal interface is usually sharp.
Tumor can invade and exit the kidney as renal vein tumor thrombi.
Tumor cells may have abundant clear cytoplasm due to lipids and glycogen. Histologic patterns may be tubular, trabecular or solid. Tumor is graded on a scale from I to IV depending on cytologic nuclear features. A sarcomatoid variant is recognized which has a worse prognosis. Patients may present with costovertebral angle pain, palpable mass and hematuria.