# Neuroblastoma Presenting as a Congenital Renal Mass in a Neonate: A Diagnostic Pitfall

## TL;DR

A neonate with a kidney mass was diagnosed with neuroblastoma, highlighting the need to consider this cancer in young infants with congenital renal masses.

## Contribution

This case emphasizes the importance of including neuroblastoma in the differential diagnosis of neonatal renal masses.

## Key findings

- Neuroblastoma can present as a congenital renal mass in neonates, especially near the adrenal gland.
- Segmental chromosomal aberrations may indicate poor prognosis even in localized infant disease.
- Genomic profiling can help guide treatment decisions in such cases.

## Abstract

What are the main findings?
Neuroblastoma should be included in the differential diagnosis of a renal mass, particularly when the lesion involves the upper pole near the adrenal gland, even though congenital mesoblastic nephroma and Wilms tumor are statistically more likely in neonates.

Neuroblastoma should be included in the differential diagnosis of a renal mass, particularly when the lesion involves the upper pole near the adrenal gland, even though congenital mesoblastic nephroma and Wilms tumor are statistically more likely in neonates.

What are the implications of the main findings?
In very young infants, imaging findings can be challenging to interpret; radiological impressions should be considered provisional.Segmental chromosomal aberrations may predict poor prognosis even in apparently localized infant disease.

In very young infants, imaging findings can be challenging to interpret; radiological impressions should be considered provisional.

Segmental chromosomal aberrations may predict poor prognosis even in apparently localized infant disease.

Background: Congenital renal masses in neonates are most commonly congenital mesoblastic nephroma or, less frequently, or Wilms tumor. We describe a neonate with an apparent primary renal tumor that proved to be adrenal neuroblastoma infiltrating the kidney, highlighting diagnostic pitfalls in this subgroup of patients. Methods: We retrospectively reviewed the diagnostic work-up, histopathology, genomic profiling, treatment, and outcome of a term neonate in whom a renal mass was detected incidentally on ultrasound. Results: Ultrasound and MRI showed a 2 cm solid lesion centered in the upper pole of the left kidney, interpreted as nephroblastomatosis/early Wilms tumor. Left nephrectomy with adrenalectomy revealed stroma-poor, undifferentiated neuroblastoma with regional node involvement and multiple segmental chromosomal aberrations, including 1p and 3p loss, but no MYCN or ALK alterations. Initial management consisted of surgery alone with close surveillance. Within weeks, early disseminated relapse with bone and soft-tissue metastases occurred, necessitating escalation to high-risk, COJEC-based chemotherapy; resection of residual mass; and modified consolidation without high-dose chemotherapy or radiotherapy. The child remains in complete remission with preserved renal function. Conclusions: Neuroblastoma should be considered in the differential diagnosis of congenital “renal” masses. Imaging-driven provisional diagnoses may be misleading, and genomic risk profiling may help lower the threshold for systemic therapy in selected cases.