Predictors of Benignity for Small Endophytic Echogenic Renal Masses

Objectives: To evaluate for distinguishing demographic and sonographic features of small (<3 cm) endophytic angiomyolipomas (AMLs) that differentiate them from endophytic renal cell carcinomas (RCCs).

Methods: This is a Health Insurance Portablitiy and Accountablity Act (HIPAA)-compliant retrospective review of the demographics and ultrasound features of endophytic renal AMLs compared to a group of endophytic RCCs. AMLs were confirmed by identifying macroscopic fat on computed tomography (CT) or magnetic resonance imaging (MRI), while RCCs were pathologically proven. Statistical analysis was used to compare findings in the 2 groups.

Results: There were a total of 66 patients with 66 AMLs, and 28 patients with 28 RCCs. Of the AMLs, 57 of 66 were in females, while 10 of the 28 RCC cases were in females (P < .0001). The mean AML long and short diameters were 11.0 × 9.3 mm and were statistically significantly smaller (P < .0001) than the diameters of the RCCs (23.4 × 22.1 mm). Likewise, the ratio of the long axis to the short axis measurement was statistically significantly different between the 2 groups (P < .0001). Of the studied sonographic features, statistically different features between AMLs and RCCs included an oval versus a round shape (P < .001), respectively, and the presence versus absence of an echogenic margin, respectively. Location of the mass, mass homogeneity, mass lobulation, and presence of cystic components were not distinguishing features using P < .01 levels.

Conclusion: For an endophytic echogenic mass in a female patient, a small size with an oval shape and an echogenic margin is statistically more likely to be an AML than an RCC, which may be helpful with management decisions.