The Wilms' tumor belongs together with neuroblastoma and rhabdomyosarcoma to the second most common solid malignancies in children, which have similar frequencies. The mean age is 3 to 4 years in nephroblastoma and 50 percentage are younger than 2 years.

1. Because the Wilms' tumor presents itself often by chance as an abdominal mass the general practitioner must consider a Wilms' tumor during a routine examination as possible explanation.
2. With early diagnosis most Wilms' tumors can be cured today

It is a congenital tumor. In 15 percent additional anomalies occur as congenital aniridia, hemihypertrophy and so forth.

Considering x-ray and operative findings, histology, molecular biology and age stages I to V have been defined.

The clinical signs and symptoms occur in the following frequency distribution:
1. Abdominal mass, which extends from the flank to the abdominal midline.
2. Abdominal pain.
3. Gross or microscopic hematuria.
4. Abdominal emergency in case of acute hemorrhage or rupture of the tumor, either spontaneously or following a minor trauma.
5. Arterial hypertension, varicocele.
6. In case of recognized malformations which may occur combined with Wilm's tumor a nephroblastoma must be excluded right away and on follow-up.

If not treated or only inadequately death (prior to the multidisciplinary and early treatment survival 20 percent).

The differential diagnosis includes other retroperinoneal tumors as neuroblastoma, teratoma, rhabdomyosarcoma, and intraabdominal tumors as malignant lymphoma, cysts and tumors of the ovary and pathologies of liver, pancreas and adrenal gland. In addition masses caused by anomalies or infections as hydronephrosis, choledochal cyst, mesenteric cyst, and abdominal abscess following appendicitis, echinococcal cyst.
The differential diagnosis includes also causes of recurrent abdominal pain, of hematuria and of abdominal emergencies.

Work-up examinations for confirmation of the diagnosis and for determination of the stage and the biology of the individual tumor. The latter decide on the treatment options and the prognosis.
Ultrasound, CT with contrast and X-rays to exclude metastatic tumor. Histological and biological work-up of the tumor tissue.

Multidisciplinary approach, sequence and type of measures depending on the stage. Often primary or less frequently secondary total resection of the tumor (nephrectomy) with exploration of the opposite kidney and biopsy of the retroperitoneal lymph nods according to the applied protocol.

Depending on the stage. Today survival between 100 and 70 pertentage. Longterm follow-up necessary due to late sequels of the treatment and secondary tumors (10 percent within 25 years).