Patient underwent left renal angiogram with embolization, followed by left nephrectomy with pathology results proving the mass to represent a giant angiomyolipoma.

Key points:

• most common benign tumor of the kidney

• 95% contain macroscopic fat, virtually diagnostic for AML (if calcifications are present, it could be an RCC)

• associated with tuberous sclerosis, where they can be bilateral

• if greater than 4 cm, portray a higher risk of bleeding and intervention may be necessary

• 5% are lipid poor (no macroscopic fat)

• don't confuse microscopic with macroscopic fat. Drop of signal on out-of-phase imaging suggests intracellular or microscopic fat, a feature that can be seen not uncommonly with clear cell carcinoma