Occurrence of extrarenal Wilms' tumour (WT) is very exceptional and the dia
gnosis is almost always made after surgical intervention. The tumour can be
located in the retroperitoneum, uterus, cervix, testes, skin and even in t
he thorax. The exact mechanism whereby a WT occurs in extrarenal tissues is
not known. The presence of ectopic metanephric blastema cells or the WT ge
ne that cause transformation of extrarenal primitive mesonephric or proneph
ric remnants into WT are both considered in the embryogenesis. Although ult
rasonography and CT scan are both helpful in the definition of retroperiton
eal tumours, there is no characteristic finding to diagnose an extrarenal W
T before surgery. However the histological characteristics are the same as
in intrarenal WT, a retroperitoneal teratoma should be clearly investigated
for a possible admixture of WT cells. Patients with extrarenal WT are give
n the same treatment protocol as patients with stage III WT. In this paper,
a 5-year-old female patient with an extrarenal WT located in the lumbosacr
al region is presented. Conclusion: as a rule, diagnosis of extrarenal Wilm
s' tumour is made after surgery. Surgical excision is the treatment of choi
ce and the same general therapeutic rules should be followed as when the ki
dney were affected. Stage III guidelines for chemotherapy and radiotherapy
are appropriate in these patients.