# Metanephric adenoma in a pediatric patient case report

## TL;DR

This case report describes a rare kidney tumor in a child, highlighting the importance of genetic testing to distinguish it from a more common pediatric kidney cancer.

## Contribution

The report emphasizes the diagnostic challenge of metanephric adenoma in pediatric patients and the role of BRAF V600E mutation testing.

## Key findings

- An 8-year-old male with a renal mass was diagnosed with metanephric adenoma after genetic testing confirmed the BRAF V600E mutation.
- Immunohistochemical markers like WT1, PAX8, and CD57 were positive, but chemotherapy was not required.
- The case highlights the need to consider metanephric adenoma in the differential diagnosis of pediatric renal tumors.

## Abstract

Metanephric adenoma (MA) is a rare benign renal tumor, with an incidence of 0.2%–1%. Approximately 90% of MA cases present with the BRAF V600E mutation. This study reports an 8-year-old male child who presented with abdominal pain for one month. Abdominal ultrasound revealed a cystic necrotic mass measuring 56 × 45 mm in the right kidney. A preliminary diagnosis of Wilms tumor (WT) led to the initiation of preoperative vincristine therapy. Right nephroureterectomy was performed by pediatric surgery. Histopathological analysis could not differentiate between MA and WT. Immunohistochemical findings were positive for WT1, PANCK (weak focal), INI1 (intact), PAX8, CD56, and CD57. Genetic testing confirmed the presence of the BRAF V600E mutation (1799T > A, 1799_1800TG > AA). The patient was diagnosed with MA and was followed without chemotherapy. In conclusion, MA, which can be mistaken for WT, should be considered in the differential diagnosis of pediatric renal neoplasms. Immunohistochemical evaluation and genetic testing are essential for a definitive diagnosis.