A case of infantile congenital mesoblastic nephroma with ETV6-NTRK3 gene fusion

Abstract

Wilms tumor is the most common pediatric renal mass, while congenital mesoblastic nephroma (CMN) is the most common renal tumor in neonates and infants under 6 months. We report a 2-month-old male with CMN. His chief symptom was persistent crying. Abdominal ultrasonography revealed a mass of 7 centimeters in diameter on the upper pole of the right kidney, but did not detect the right adrenal grand. Laboratory examinations revealed that his neuron-specific enolase (NSE) level was elevated, and thus neuroblastoma was tentatively diagnosed. However, MRI and CT revealed it was a renal tumor. An NSE-producing Wilms tumor was suspected, but CMN was diagnosed considering his age and radiographic characteristics. The tumor was completely resected with unilateral nephrectomy. Histological examination confirmed a diagnosis of cellular-type CMN with EVT6-NTRK3 gene fusion. Adjuvant therapy was not administered because the surgical margin was pathologically negative and no residual uptake was detected in whole-body PET-CT. An onset age ≥3 months and cellular-type CMN at stage III are risk factors for relapse; therefore, adjuvant therapy was previously recommended. However, recent reports demonstrated that patients with cellular-type CMN and ETV6-NTRK3 translocation have a good prognosis. CMN is rare and further studies are expected.