Flat in situ carcinoma of the bladder: cytological examination of urine in diagnosis, follow up, and assessment of response to chemotherapy.

Urine cytology was performed for the diagnosis and follow up of flat carcinoma in situ (CIS) of the bladder in a series of 35 patients without associated or previous bladder tumours. Ninety six per cent had positive or suspicious cytology at initial presentation. There were no false positive reports. Cytological diagnosis of malignancy was made before biopsy in 24 patients: CIS in voided urine presents as flat sheets of five to 15 cells with features of high grade malignancy. Development of tumour during follow up was suggested by the appearance of large thick sheets and clusters of 30 or more malignant cells which were large and pleomorphic in high grade tumours and relatively small and closely cohesive in low grade tumours. Eleven of 13 patients with these clusters had bladder or ureteric tumours and two had malignant disease in the prostate. Negative cytological results in the presence of degenerative changes caused by chemotherapy was an unreliable indicator of response to chemotherapy, and there were five patients with false negative reports during treatment, of whom three had developed tumour. Persistence of malignant cells with features similar to those seen in the urine before treatment reliably predicted failure to respond to chemotherapy.