How can renal masses be classified?

Malignant (carcinoma, lymphoma, leiomyosarcoma, liposarcoma, rhabdomyosarcoma, metastasis, invasion, wilm's tumor) Benign (simple cyst, angiomyolipoma, oncocytoma) Inflammatory (abscess, pyelonephritis, Xanthogranulomatous pyelonephritis, TB, infected cyst, rheumatic granuloma.)