Giant Epithelioid Angiomyolipoma: An Imaging-related Differential Diagnosis Among Fat-containing Renal Masses

Angiomyolipomas (AMLs) are among the most common benign renal tumors, typically consisting of varying proportions of 3 components: blood vessels (angio), smooth muscle cells (myo), and fatty tissue (lipoma), and are thus called triphasic. Occasionally, AMLs may present atypical histologic features consisting almost exclusively of one component (monophasic) or containing numerous epithelioid muscle cells with small amount of fat, as in the rare epithelioid variant (E-AMLs). AMLs occur as a sporadic entity in 80% of cases; more rarely, they are related to hereditary diseases such as tuberous sclerosis complex (TSC). Hereditary AMLs can reach huge dimensions and may present unusual imaging features determining diagnostic pitfalls. Few cases of giant sporadic AMLs are reported in literature, and even fewer regarding the epithelioid variant. We present a case of a 36-year-old man suffering from anemia and fever, whose contrast-enhanced computed tomography (CT) depicted the presence of a huge (14 x 21 x 30 cm) retroperitoneal fat-containing mass.