Papillary urothelial neoplasms of low malignant potential. Clinical and biologic implications

Background: Knowledge of the long term outcomes of patients with papillary urothelial neoplasms of low malignant potential (LMP) is limited.

Methods: The authors studied 112 consecutive patients who were diagnosed with papillary urothelial neoplasms of LMP (formerly Ta, World Health Organization Grade 1 of 3 papillary urothelial carcinoma) at the Mayo Clinic between 1958 and 1963. All histologic slides were reviewed and fulfilled the diagnostic criteria of the 1998 World Health Organization/International Society of Urological Pathology classification system.

Results: Patient age at diagnosis ranged from 33 to 99 years (mean, 65 years). The male-to-female ratio was 3:1. The mean follow-up was 12.8 years (range, 0.1-35 years; median, 11.7 years). Twelve patients had biopsy-proven, noninvasive urothelial carcinoma; 17 patients had cystoscopically detected recurrences (all were treated by fulguration without biopsy); and 4 patients developed invasive urothelial carcinoma (including 2 with muscle-invasive carcinoma). Twelve (75%) of 16 patients with biopsy-proven recurrence or progression had cancer dedifferentiation, which resulted in a diagnosis of higher grade cancer than was indicated on initial biopsies. The mean interval from initial diagnosis to development of invasive carcinoma was 13.3 years (range, 10-14 years). Three patients died of bladder cancer.

Conclusions: Patients with papillary urothelial neoplasms of LMP have increased risks of local recurrence, progression, and death from bladder carcinoma. Long term clinical follow-up may be indicated for patient management.