Retroperitoneal extrarenal angiomyolipomas: an evidence-based approach to a rare clinical entity

Abstract

Extrarenal angiomyolipomas (ERAMLs) are rare tumors that present as incidentalomas upon imaging for other conditions. Retroperitoneal ERAMLs present a unique challenge from a diagnostic and treatment standpoint as they can mimic other benign and malignant retroperitoneal tumors. We present a case of a 39-year-old female with a 19.3 cm × 13.5 cm × 10.7 cm left extrarenal retroperitoneal mass. Histopathologic examination and HMB-45 staining revealed the mass to be a retroperitoneal ERAML. Our case report provides a comprehensive literature review and an evidence-based algorithm for taking care of patients with ERAMLs.

Figure 1

(a) oral contrast and (b) IV and oral contrast: abdominal computerized tomography demonstrating an encapsulated fatty vascular mass (white arrows) lateral to the left kidney measuring 19.3 cm × 13.5 cm × 10.7 cm with prominent vascular dependence on the left renal vein and artery as well as a 2 cm posterior mid-pole homogeneous fatty density (yellow arrow). Left colon is laterally displaced (orange arrow).

Figure 2

Abdominal magnetic resonance imaging demonstrating a large fatty encapsulated mass (white asterisk) measuring 19.3 cm × 13.5 cm × 10.7 cm with prominent vascularity (white arrows). The anatomic relationship between the mass and the left kidney can be well seen in Figure 2(b).

Figure 3

Gross image of the en bloc resected mass including the left kidney (black arrow), demonstrating a well-encapsulated fatty mass attached to the upper pole of the kidney (white arrow) with a smooth outer surface measuring 23 cm × 14 cm × 9 cm.

Figure 4

Extrarenal mass (Hematoxylin and Eosin). Photomicrograph of the mass demonstrate mature adipose tissue with a tortuous thick blood vessel (black arrow) ((a); ×20) and bundles of smooth muscles lacking elastic tissue lamina ((b); ×40), adipose tissue with small areas of smooth muscle with epithelioid features ((c); ×40). Focal staining with HMB45 antibody was positive (blue star) ((d); ×40), consistent with angiomyolipoma.