Are papillary lesions of the urinary bladder: usually Benign and low-grade?

Not usually benign. They need to be removed. If they are indeed low grade, the usual protocol is for the urologist to schedule cystoscopy every three months for two years since low grade bladder cancer has a nasty little habit of recurring. If a patient is still clear after two years the exams are done every six months until five years have passed then annually forever.