Renal Angiomyolipoma

Renal angiomyolipomas are the most prevalent benign renal tumor. First described by Grawitz in 1900, renal angiomyolipomas are generally highly vascular tumors primarily composed of blood vessels, smooth muscles, and mature adipose tissues and are distinguished by perivascular epithelioid differentiation. Although most of these tumors are often discovered incidentally during radiological imaging, symptomatic presentations such as flank pain, gross hematuria, or severe retroperitoneal hemorrhage may also exist.  Angiomyolipomas are occasionally misidentified as hamartomas. However, while both are benign, the distinction lies in their nature—an angiomyolipoma is a genuine tumor, whereas a hamartoma constitutes a disorganized aggregation of normal local tissue and cells, often resulting from trauma, infection, infarction, obstruction, or hemorrhage. Notably, although Grawitz first described renal angiomyolipomas, they are distinct from Grawitz tumors, which are malignant renal cell carcinomas and hypernephromas. Imaging plays a central role in the diagnosis and management of renal angiomyolipomas. These tumors comprise variable amounts of 3 tissue elements—vascular, muscular, and adipose. These variations manifest in distinct pathological, radiological, and clinical features.  The key diagnostic criterion of classic angiomyolipoma is identifying a significant amount of adipose tissue on radiological imaging. Although considered benign, the tumors may extend into the surrounding perirenal fat or renal sinus, as well as nearby organs and lymphatics. Rare reports also indicate isolated instances of tumor thrombi extending through the renal vein into the vena cava. Management of angiomyolipomas is determined by factors such as clinical symptoms, tumor size, number, growth pattern, and potential for malignancy. For instance, epithelioid angiomyolipoma of the kidney, a rare subtype of angiomyolipoma, is regarded as potentially malignant.