Intravesical instillation of mitomycin C is a routine practice for treatment of superficial transitional cell carcinoma of bladder. Despite usual precautions serious side effects like fistulation can occur with diverse presentation as illustrated by this report. The pathology demonstrates a dense necrotic and massive inflammatory reaction in the peri vesical tissue following the extravasation of an intravesically administered chemotherapeutic agent. The severe inflammatory tissue response and the necrotic effect associated with the extravasated chemotherapeutic agent could potentially lead to local sepsis with a subsequent fistula formation.