Bladder tumors rarely occur in the first two decades of life, and, in contrast to the cases in adults, 97% of transitional cell carcinomas of the bladder in childhood are low grade, superficial, and of good prognosis, with a progression rate of only 2% to 4%. This report presents a case of low-grade bladder cancer in a 17-year-old patient which behaved quite aggressively. The most striking features of this case included the histopathologic findings and rapid disease progression, despite treatment with agents known for their efficacy against tumors of epithelial and mesenchymal origin.