Wilms' tumor or nephroblastoma is cancer of the kidneys thattypically occurs in children,rarely in adults.
The majority (75%) occurs in otherwise normal children; a minority (25%) isassociated with other developmental abnormalities. It is highly responsive totreatment, with about 90% of patients surviving at least five years.
Most nephroblastomas are unilateral, being bilateral in less than 5% ofcases. They tend to be encapsulated and vacularized tumors that do not crossthe midline of the abdomen. In cases of metastasis it is usually to the lung. Arupture of Wilms tumor put the patient at risk of hemorrhage and peritoneal disseminationof the tumor. In such cases, surgical intervention by a surgeon who isexperienced in the removal of such a fragile tumor is imperative.
Pathologically, a triphasic nephroblastoma comprises three elements:
Wilms' tumor is a malignant tumor containing metanephric blastema, stromal andepithelial derivatives. Characteristic is the presence of abortive tubules andglomeruli surrounded by a spindled cell stroma. The stroma may include striatedmuscle,cartilage,bone, fat tissue, fibroustissue. The tumor is compressing the normal kidney parenchyma.
The mesenchymal component may include cells showing rhabdomyoiddifferentiation. The rhabdomyoid component may itself show features ofmalignancy (rhabdomyosarcomatous Wilms).
Wilms tumor may be separated into 2 prognostic groups based on pathologiccharacteristics:
- Favorable - Contains well developed components mentioned above
- Anaplastic - Contains diffuse anaplasia (poorly developed cells)