Despite the rather bland cellular features (small nuclei, large cytoplasm) I think this is a carcinoma due to the deep infiltration.  
If You agree: which subtype ?  
Thanks !

I think that's the nested variant of invasive urothelial carcinoma as an aggressive tumor with a rather bland cytology and similarities to v. Brunn's cell nests.

Indeed nested variant of urothelial carcinoma is a differential diagnosis. A considerable Brunn`s nest hyperplasia should be ruled out. Is there any mucin secration ? If so this will again leads us to another differential diagnosis, Cystitis glandularis or urothel carcinoma with glandular differentiation. Please send me a parrafin block. i will do some immune.  
 
Seife Hailemariam

Thank you for sending the tissue block of this difficut case.The immunohistochemistry findings are against bladder cancer. No reaction for p53, positive for CD44 and umbrella cells with strong CK 20 positivity. Our diagnosis is of course not based only on immunohistochemistry. The overall structur of the tumor shows organoid patter. We seeked third opnion from prof. Bubendorf Uni.Basel and he also faviours a benign diagnosis.  
This is an unusual Brunn`s nest hyperplasia. It will be of great interest to get more information about the cytoscopic finding.