A 28-year-old female complained of minimal fever elevation. Computed tomography (CT) revealed a left renal tumor of 10 cm in diameter. Ultrasonogram and CT, magnetic resonance imaging and angiography suggested a renal angiomyolipoma (AML) with marked extrarenal development. Partial nephrectomy was performed using a microwave tissue coagulater without clamping of the renal artery. The tumor weight was 800 g and the pathological diagnosis was AML. The management of large AML is reviewed in the literature. Nephron sparing surgery should be performed even in patients who have a larger tumor with extrarenal development.