Inflammatory Myofibroblastic Tumor
The lesion consists of stellate or spindle cells arranged haphazardly in abundant myxoid stroma creating a "tissue culture" appearance. A delicate vascular network with extravasated red blood cells can be seen. Mitotic activity is usually increased, but atypical mitotic figures are not seen. Inflammatory myofibroblastic tumor is locally invasive and can even destroy bladder muscle.