FISH test results

I`m a 56 year old male,I have a long( 35 year ) history of BPH/ chronic Cystitis problems, but recently had a urine cell cytology that showed "atypical cells". My Uro ordered a Fish test,PSA and CT urogram. The CT and PSA came back fine, but the FISH test was positive. I`m now scheduled for a cysto and biopsy,ect. My Uro said that he wasn`t totally convinced that my FISH result meant cancer,and said that sometimes infection or chronic inflamation (inflammation) could cause this result. Is this just my Uro trying not to worry me until he can do the cysto,ect, or is a positive FISH result always indicative of cancer and nothing else?