This study aims to investigate the relation of mast cell (MC) accumulation with tumor grade and stage in urothelial carcinomas of the urinary bladder and to determine its relationship with angiogenesis. A total of 78 urothelial carcinomas obtained by transurethral resection were investigated immunohistochemically by using c-Kit (CD117) and anti-CD34. The correlation between MC counts and microvessels was evaluated and compared with histopathologic parameters including tumor stage and grade. There were significant correlations between MC counts, grade, and stage (P <.05; r = 0.69 and 0.63, respectively). However, MC counts in adjacent nontumoral bladder mucosa significantly were higher than the MC counts in tumoral zone (P <.001). On the other hand, significant correlation was found between the number of MCs in tumoral zone and the microvessel density (P <.05, r = 0.56). The results of our study suggest that c-Kit positive MCs in tumoral zone may contribute to tumor angiogenesis and play a significant role in tumor growth and invasion. Further studies are needed to support these observations. © 2012 Elsevier Inc. All rights reserved.