Radiological classifications of renal angiomyolipomas based on 127 tumors

Purpose: Demonstrate radiological findings of 127 angiomyolipomas (AMLs) and propose a classification based on the radiological evidence of fat. Materials and Methods: The imaging findings of 85 consecutive patients with AMLs: iso-lated (n = 73), multiple without tuberous sclerosis (TS) (n = 4) and multiple with TS (n = 8), were retrospectively reviewed. Eighteen AMLs (14%) presented with hemorrhage. All patients were sub-mitted to a dedicated helical CT or magnetic resonance studies. All hemorrhagic and non-hemor-rhagic lesions were grouped together since our objective was to analyze the presence of detectable fat. Out of 85 patients, 53 were monitored and 32 were treated surgically due to large perirenal compo-nent (n = 13), hemorrhage (n = 11) and impossibility of an adequate preoperative characterization (n = 8). There was not a case of renal cell carcinoma (RCC) with fat component in this group of patients. Results: Based on the presence and amount of detectable fat within the lesion, AMLs were classified in 4 distinct radiological patterns: Pattern-I, predominantly fatty (usually less than 2 cm in diameter and intrarenal): 54%; Pattern-II, partially fatty (intrarenal or exophytic): 29%; Pattern-III, minimally fatty (most exophytic and perirenal): 11%; and Pattern-IV, without fat (most exophytic an