Falsely positive urinary cytology: pathologist's error or preclinical cancer?

The reluctance to accept urinary cytology as a diagnostic procedure in urologic cancer has been partially owing to a relatively high incidence of falsely positive results. The recent recognition of bladder cancer as a field change and the identification of urothelial dysplasia support the contention that these cytologic findings represent early neoplasia rather than laboratory errors. Of 64 patients with positive or suspicious urinary cytology short-term histologic confirmation could not be obtained in 10. Of these 10 patients review of the clinical and pathologic material was possible in 9 and significant urologic abnormalities were found in 7. Among patients with bladder cancer there were no falsely negative reports. Urinary cytology is a reliable procedure in the diagnosis of urologic malignancies. Unconfirmed positive results require careful examination and followup.