Metanephric Adenoma with Polycythaemia in an Adolescent: Diagnostic and Pathological Challenges —A Case Report

We report a 14-year-old girl presenting with flank pain, microscopic haematuria, and polycythaemia. Imaging demonstrated a well-defined upper pole renal mass with minimal enhancement, while image-guided biopsy suggested metanephric adenoma but remained inconclusive. She underwent open partial nephrectomy, and histopathology confirmed metanephric adenoma despite atypical immunohistochemistry. Postoperative recovery was uneventful with preserved renal function, and polycythaemia resolved completely. This case highlights the diagnostic challenges of differentiating benign from malignant renal tumours in young patients and supports nephron-sparing surgery as an effective management approach.