Thickened urinary bladders are usually the result of interstitial cystitis rather than neoplasia. The histologic appearance is epithelial ulceration and osmotic mural edema without any significant lymphocytic infiltration. The lesion is qualitatively indistinguishable from urinary epithelial ulceration caused by urinary calculi. Multifocal ulceration gives rise to really impressive multifocal edema or its sequel of papillary reparative epithelial hyperplasia, both of which can easily be mistaken for neoplasia. The microscope is magical!

Transitional cell carcinoma can be diagnosed on direct or (better) sedimented samples of urine, but many cytologists will be cautious in making the diagnosis if there is any evidence of concurrent inflammatory disease. Transitional epithelium is notorious for its tendency to become dysplastic (hyperchromasia, anisokaryosis, binucleation) in the face of ongoing irritation of any type, and so the risk of over-diagnosing transitional cell carcinoma is substantial. There are number of techniques using catheter tips and other devices to perform "traumatic flushes" of the urethra that will dislodge chunks of tissue large enough for histologic assessment. Anything that will get even tiny histology samples is greatly preferred over cytology, and the diagnosis can usually be made with a high degree of confidence.