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

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

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.

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.

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.