Imaging manifestations of congenital mesoblastic nephroma

Abstract

Objective: Congenital mesoblastic nephroma (CMN) is a rare renal tumor mainly observed in infants and young children. This study aims to analyze the imaging manifestations of CMN to improve the understanding of the disease.

Methods: The imaging manifestations and clinical records of all pediatric patients with CMN admitted to our hospital over the last 7 years were retrospectively analyzed. The diagnosis of CMN was confirmed by postoperative pathology. All patients underwent computed tomography (CT) scans; 2 patients additionally underwent magnetic resonance imaging (MRI) scans (including one prenatal MRI scan).

Results: We evaluated 10 pediatric patients (6 males and 4 females) aged 7 days to 12 months (median age: 4 months) with CMN located on the left kidney in six cases and the right kidney in four cases. The CT imaging manifested as solid lesions (5 cases), solid-cystic lesions with solid predominance (4 cases), or solid-multicystic lesions with cystic predominance (1 case). Enhanced CT showed moderately and heterogeneously enhanced solid component and intracystic septations at the corticomedullary phase that were further enhanced at the nephrographic phase, although their CT values were still lower than those of the renal parenchyma. The "double-layer sign" were seen in 4 cases of classic type of CMN, and the "intratumor pelvis sign" were seen in 9 cases that include 5 classic, 3 cellular and 1 mixed type of CMN. In the 2 patients who underwent MRI, the scans showed solitary masses. The lesions had hypointense signals on the T1WI sequence and isointensity or slightly lower-intensity signals than the surrounding renal parenchyma on the fluid-sensitive sequences, whereas the lesions showed hyperintense signals on the diffusion-weighted imaging (DWI) sequence.

Conclusions: The imaging manifestations of CMN are closely correlated with the pathological subtype and have certain characteristics. The "double-layer sign" was seen with most classic type CMN, and "intratumor pelvis sign" was seen in 90% cases.

Keywords: CT; Congenital mesoblastic nephroma; Double-layer sign; Intratumor pelvis sign; MRI.