Adult Wilms tumour with diffuse anaplasia: A rare diagnostic pitfall and therapeutic challenge

A 20-year-old man presented with right flank pain and gross haematuria from a large right renal mass that enlarged rapidly over five months. Open radical nephrectomy with hilar node sampling revealed monophasic blastemal Wilms tumour with diffuse anaplasia; all nodes were negative. He later developed pulmonary metastases and, after treatment interruption, pulmonary relapse, managed with multi-agent chemotherapy, radiotherapy and salvage chemotherapy achieving complete response. Adult Wilms tumour is rare, mimics renal cell carcinoma and carries a poor prognosis. This case highlights its diagnostic difficulty, high-risk histology and the critical importance of sustained treatment adherence.