Papillary urothelial neoplasm of low malignant potential: real-world diagnostic pitfalls and clinical outcomes from a case series

Papillary urothelial neoplasm of low malignant potential (PUNLMP) is an uncommon non-muscle-invasive bladder tumor. Its indolent nature often leads to underestimation of diagnostic complexity and recurrence risk, particularly in real-world practice where pathological distinction from low-grade carcinoma can be subtle. To characterize the clinical, imaging, and pathological profiles of PUNLMP in a contemporary cohort, with a specific exploratory focus on diagnostic misclassification rates and treatment patterns, contextualized by a systematic review of the literature. This was a retrospective case series of five patients with histologically confirmed PUNLMP following transurethral resection of bladder tumor (TURBT) at a single tertiary center (2023–2024). We collected comprehensive data on demographics, imaging, pathology, surgical management, and follow-up outcomes (median follow-up: 12 months; range 12–24). A systematic review of PubMed and Web of Science (2005–2024) was performed to synthesize existing evidence on recurrence and progression. The cohort comprised three males and two females, with a median age of 54 years (range, 25–76). Mean tumor diameter was 1.54 cm. Notably, two of five cases (40%) were initially misclassified as low-grade urothelial carcinoma on preliminary pathological review, representing an exploratory observation of real-world diagnostic pitfall. All patients underwent complete TURBT followed by a single immediate intravesical chemotherapy instillation. During follow-up, one patient (20%) experienced a local recurrence (PUNLMP) at 12 months, with no progression observed. Pooled analysis of 453 cases from seven eligible studies showed the overall recurrence rate of PUNLMP was 21.2% (95%CI: 17.7%–25.2%, I² = 0%) calculated via generalized linear mixed models, and a pooled progression rate below 2% estimated by the DerSimonian–Laird method. Subgroup analysis showed no significant difference in recurrence between adult and paediatric cohorts ( P = 0.6845). TURBT plus immediate intravesical instillation represented the predominant adult management strategy. This exploratory case series suggests that PUNLMP carries a non-negligible recurrence risk despite its low malignant potential. The preliminarily observed initial misclassification rate highlights the potential value of standardized pathological review. Our findings advocate for risk-adapted surveillance rather than a one-size-fits-all low-risk protocol, pending validation in larger prospective cohorts.