Pathology
Most nephroblastomas are unilateral, being bilateral in less than 5% of cases, although patients with Denys-Drash syndrome mostly have bilateral or multiple tumors. They tend to be encapsulated and vascularized tumors that do not cross the midline of the abdomen. In cases of metastasis it is usually to the lung. A rupture of Wilms' tumor puts the patient at risk of hemorrhage and peritoneal dissemination of the tumor. In such cases, surgical intervention by a surgeon who is experienced in the removal of such a fragile tumor is imperative.
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.
The mesenchymal component may include cells showing rhabdomyoid differentiation. The rhabdomyoid component may itself show features of malignancy (rhabdomyosarcomatous Wilms).
Wilms' tumors 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)
Read more about this topic: Wilms' Tumor
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