While bathing her newly-received 2-year-old son, a foster mother feels a mass in his abdomen. A thorough medical evaluation of the child reveals aniridia, hypospadias, horseshoe kidney, and hemihypertrophy. Which of the following is the most likely diagnosis for this child?
a) Beckwith-Wiedemann syndrome
b) Wilms tumor
c) Fanconi anemia
d) Neurofibromatosis type 1
