Role of Angular Interface Sign in Characterizing Small Exophytic Renal Masses in Computed Tomography; Prospective Study

The widespread use of computed tomography (CT) has increased the incidence of small renal cell masses. We aimed to evaluate the usefulness of the angular interface sign (ice cream cone sign) to differentiate a broad spectrum of small renal masses using CT. The prospective study included CT images of patients with exophytic renal masses ≤ 4 cm in maximal dimension. The presence or absence of an angular interface of the renal parenchyma with the deep part of the renal mass was assessed. Correlation with the final pathological diagnosis was performed. The study included 116 patients with renal parenchymal masses of a mean (± SD) diameter of 28 (± 8.8) mm and a mean age of 47.7 (±12.8) years. The final diagnosis showed 101 neoplastic masses [66 renal cell carcinomas (RCC), 29 angiomyolipomas (AML), 3 lymphomas, and 3 oncocytomas] and 15 non-neoplastic masses [11 small abscesses, 2 complicated renal cysts, and 2 granulomas]. Angular interface sign was statistically comparable in neoplastic versus non-neoplastic lesions (37.6% versus 13.3%, respectively, P = 0.065). There was a statistically higher incidence of the sign when comparing benign versus malignant neoplastic masses (56.25 vs. 29%, respectively, P = 0.009). Also, comparing the sign in AML versus RCC was statistically significant (52% of AML versus 29% of RCC, P = 0.032). The angular interface sign seems beneficial in predicting the nature of small renal masses. The sign suggests benign rather than malignant small renal masses.