A healthy appearing, 8-year-old boy is evaluated for an abdominal mass, felt by his mother during a bath. What is the most likely diagnosis?

Typically Wilms' tumor is noted in well appearing children in the second half of their first decade of life. These masses are usually felt or visually noted by parents during routine daily activities. Children with neuroblastoma are usually younger and appear quite sick. Although unlikely, renal cell carcinoma has been reported in children and diagnosis is only based on final pathology results. Lymphoma should be ruled out based on CT scan findings and subsequent needle-guided biopsy, since treatment is usually nonsurgical.