Malignant angiomyolipoma: a rare entity with unusual biology.

The authors present an interesting case of a very rare renal neoplasm, malignant epithelioid angiomyolipoma (AML), which belongs to a family of mesenchymal tumors known as perivascular epithelioid tumors (PEComas). In the modern era, benign renal AML typically presents incidentally; it is most commonly found on a CT scan obtained for other purposes. A minority of patients present with hematuria, flank pain, or a palpable mass; presentation with unexplained anemia, as in this case, is decidedly unusual. Presentation with life-threatening hematuria, the so-called Wunderlich syndrome, is fortunately very rare.