Wilms Tumor

Wilms tumor is responsible for 5% of pediatric malignant tumors or approximately 500 new cases each year in the United States, with equivalent frequency in boys and girls. The incidence is fairly uniform throughout the world, being somewhat more common in black children and less common in Asian compared with white children. The mean age at presentation is 3 years for sporadic and 2 years for hereditary cases.

Children who have Wilms tumor often present with an asymptomatic abdominal mass, found by caregivers or pediatricians. The differential diagnosis for a toddler who has an abdominal mass includes neuroblastoma, hepatoblastoma, sarcoma, lymphoma, and germ cell tumors, as well as benign conditions. At times, patients newly diagnosed as having Wilms tumor experience abdominal pain and hematuria from invasion of the renal pelvis or hypertension from compression of the renal artery, each consequence occurring in approximately 25% of cases.

The most common sites of metastasis of a Wilms tumor are abdominal lymph nodes, followed by asymptomatic parenchymal lung lesions and, less often, liver nodules. In contrast to neuroblastoma or sarcomas, Wilms tumor only rarely spreads to bone or bone marrow; as a result, patients do not experience bone pain, fractures, or low blood cell counts, and even children who have advanced stage disease often appear relatively well.

Wilms tumor is associated with several genetic syndromes that can affect the clinical presentation. The WAGR syndrome, consisting of Wilms tumor, aniridia, genitourinary (GU) anomalies, and developmental retardation, results from germline inheritance of a deletion at chromosome 11p13 that involves the WT1 gene and neighboring genes that affect eye and cognitive development. WT1 is a transcription factor that …