Extrarenal Wilms tumour.

Introduction: Nephroblastoma is one of the most common solid tumours in children. It also is the most frequent tumour found in the kidneys. In 5 % of cases it affects both kidneys at the same time. About 70 - 80 new cases of Wilms tumour are registered in Poland annually, usually in patients aged from 1 to 7 years. Extrarenal Wilms tumours are extremely rare. Due to its rarity, series with more cases are based upon material collected from many clinical centers.

Aim: We would like to present a case of a boy in whom we diagnosed nephroblastoma in the retroperitoneal space 14 years after he had completed a complex therapy for bilateral Wilms tumour.

Conclusion: The development of an extrarenal tumour 14 years after complex treatment for bilateral nephroblastoma is related to the survival of metanephros located outside the kidney.