Renal Angiomyolipoma: What the Radiologist Needs to Know

Renal angiomyolipoma (AML) is the most common benign solid renal neoplasm seen in daily clinical practice, with an estimated prevalence of 0.2% to 0.6%.1 It is a triphasic mesenchymal neoplasm composed of varying amounts of dysmorphic vasculature, smooth muscle, and mature adipocytes. Pathologically, AML is now considered among the family of perivascular epithelioid cell tumors. Approximately 80% of cases are sporadic, with mean age at presentation being 43 years and most cases identified at fourth to sixth decades of life. There is also a strong female predilection, with female-to-male ratio of 4:1 in sporadic cases.1 Twenty percent of cases are associated with tuberous sclerosis (TS). Of note, AMLs may also be found in patients with lymphangioleiomyomatosis. AMLs are often found incidentally in imaging done for other purposes, but if symptomatic, they present most frequently with retroperitoneal hemorrhage, which can be fatal. The shock due to severe hemorrhage from rupture has been described in the literature as Wunderlich syndrome. Patients may present with multiple other symptoms and signs, including palpable mass, flank pain, hematuria, or renal failure. Although AML is almost always benign, a rare potentially malignant variant named epithelioid angiomyolipoma is described, which may mimic renal cell carcinoma (RCC).2.