E1171. Angiomyolipoma Revisited: Imaging Evaluation and Current Management Strategies from a Radiologist’s Perspective
  1. Felipe Mendez; University of Miami - Jackson Memorial Hospital
  2. Adriana Falcon Vazquez; University of Miami - Jackson Memorial Hospital
  3. Matthew Mason; University of Miami - Jackson Memorial Hospital
  4. Francesco Alessandrino; University of Miami - Jackson Memorial Hospital
Renal angiomyolipomas (AMLs) are the most common benign solid tumor of the kidney. Histologically, they are usually composed of smooth muscle, blood vessels, and adipose tissue. Most AMLs are easily identifiable on imaging such as CT or MR on the basis of fat content, resulting in a straightforward diagnosis through imaging. However, a small percentage of AMLs have atypical findings such as low fat content, thus making radiological diagnosis challenging. Recent updates in terminology and classifications have assisted radiologists in diagnosing AMLs tumors with atypical features using quantitative CT and MRI criteria that are easily applied to clinical practice. Indications for surveillance, biopsy or surgery have also been updated with the use of novel imaging techniques. The purpose of this review is to summarize the typical and atypical imaging features of AMLs and contrast these features with imaging pitfalls of other pathologies that may be confused for AMLs. We will also review the management of AMLs and the imaging implications of certain treatments.

Educational Goals / Teaching Points
Outline the typical and atypical imaging features of Angiomyolipoma (AML) and its subtypes. List potential pitfalls of AML and their imaging features. Summarize relevant updates in AML management with imaging implications.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
Histologic classification of AML: typical (triphasic) and atypical (monophasic or epithelioid). Radiologic classification of AML with typical multimodality imaging findings an overview: fat-rich AML, fat-poor AML, and fat-invisible AML. Multimodality imaging findings of atypical AML: tuberous sclerosis AML, epithelioid variant AML, AML with epithelial cysts (AMLEC), hemorrhagic AML, and local infiltration. Pitfalls: clear cell renal cell carcinoma, liposarcoma, oncocytoma, Wilm’s tumor, adrenal myelolipoma, and perirenal fat entrapment/renal junctional parenchymal defect. Current management of AML and updated treatment: role of biopsy, active surveillance, nephron sparing surgery, renal artery embolization, radiofrequency or cryo-ablation, and mTOR inhibitor treatment. For all cases, imaging examples will be provided.

Renal AML demonstrates a classic imaging appearance, partly on the basis of being a fat-rich renal lesion. However, AML may present with atypical imaging features that overlap with other renal diseases. Identification of these atypical features and imaging pitfalls is important for radiologists to make a proper diagnosis that will inform further management. This review summarizes such pitfalls and explores relevant updates and imaging implications of various treatment methods of AML, such as embolization and mTOR inhibitor therapy.