Atypical cytology but negative cytoscopy

Hello,
I had a urine cytology report which was indeterminate for malignancy.  I had altered n/c ratio, some enlarged nuclei in clusters.  Follow-up cystoscopy was normal.  Scheduled for repeat cystoscopy in 3 months.  My question is how often to you see an atypical cytology like this, but no cancer found?  Is it just an anomaly that can come and go?  Or does it mean that cancer is present, or will soon be present, but just hasn't gotten to a stage where it can be determined yet?  Thank you.