Unique CT Imaging Features of Congenital Mesoblastic Nephroma: Insights from a Case Series and Literature Review

Abstract Congenital mesoblastic nephroma (CMN) is a rare pediatric renal neoplasm, affecting primarily infants, accounting for 3 to 6% of pediatric renal tumors. It is subdivided into three variants: classic, cellular, and mixed, each demonstrating distinct imaging characteristics. Radiological diagnosis remains challenging due to its rarity and overlapping imaging features with other renal tumors. In this study, computed tomography (CT) scan of three cases of CMN were retrospectively analyzed and an attempt was made to identify distinct CT imaging features that may aid in accurate diagnosis of CMN. Findings like discontinuous cortex sign, branching vessel encasement, and renal pelvis involvement may be potential diagnostic signs for CMN. The abovementioned imaging findings were compared with other pediatric renal tumors, including Wilms' tumor, clear cell sarcoma, and rhabdoid tumor focusing on characteristics like vessel encasement, subcapsular extension, renal pelvis involvement, and presence of hemorrhage and necrosis within the mass. Additionally, the significance of findings like multifocality, vascular invasion, and thrombosis and extrarenal features like nodal and distant metastasis has also been discussed as an essential aid in differentiating other renal tumors.