Wilms' tumor pathophysiology

Pathology
Pathologically, a triphasic nephroblastoma comprises three elements:
 * blastema
 * mesenchyme
 * epithelium

Wilms' tumor is a malignant tumor containing metanephric blastema, stromal and epithelial derivatives. Characteristic is the presence of abortive tubules and glomeruli surrounded by a spindled cell stroma. The stroma may include striated muscle, cartilage, bone, fat tissue, fibrous tissue. The tumor is compressing the normal kidney parenchyma. Pathology images

The mesenchymal component may include cells showing rhabdomyoid differentiation. The rhabdomyoid component may itself show features of malignancy (rhabdomyosarcomatous Wilms).

Wilms tumor may be separated into 2 prognostic groups based on pathologic characteristics:
 * Favorable - Contains well developed components mentioned above
 * Anaplastic - Contains diffuse anaplasia (poorly developed cells)

Molecular biology
Mutations of the WT1 gene on chromosome 11 are observed in approximately 20% of Wilms' tumors. At least half of the Wilms' tumors with mutations in WT1 also carry mutations in CTNNB1, the gene encoding the proto-oncogene beta-catenin.

A gene on the X chromosome, WTX, is inactivated in up to 30% of Wilms' tumor cases, according to research published in 2007.