(also called transitional cell papilloma), an epithelial tumour
abnormalities covered with urothelium-like cell layers. Many consider it to be stage 0 bladder carcinoma
. About 2 - 3% of all primary bladder tumours belong to this category. There are, however, a few patients who have had papillary lesions lined by transitional cells that are normal on cytology without the presence of mitosis. The lesions are benign
at the time of local resection but have a recurrence rate of approximately 50%, with 10% developing transitional cell carcinoma
. 50% of females and 30% males with bladder papilloma will develop malignancy in a nonurologic site.
Papilloma seems to have a better prognosis than grade I papillary carcinoma. The differentiation requires biopsy and histology, and even then it may be difficult.
On imaging, bladder papillomas produce nonspecific intravesical filling defects. CT and ultrasound (US) will be able to differentiate soft tissue thickening and calcification, and contrast enhanced CT will additionally differentiate between blood clot and tumour. They may also produce obstruction of one or both ureters.
Urography is the most sensitive method of detecting small occult upper urinary tract urothelial lesions in association with papillomas of the bladder. CT, US and MRI are helpful for evaluating the extent, recurrence and cause of obstruction to the urinary tract.