Clinical impact of second opinion consultation in bladder biopsies and transurethral resection of bladder tumors.

Accurate evaluation of bladder biopsies and transurethral resection of bladder tumors (TURBTs) is essential for appropriate clinical management, yet diagnostic variability remains a challenge. We evaluated a cohort of second-opinion consultations (n = 3125) and institutional tissue reviews (n = 754) of bladder biopsies and transurethral resection of tumors (TURBT) performed at our institution. The cohort included 3879 consultations selected from 10,509 bladder specimens evaluated between January 2019 and December 2025. Original diagnoses were compared with consultation diagnoses. Overall, diagnostic discrepancies were common and frequently clinically significant. Tumor grade discrepancies were identified in 7% of patients (n = 270), morphologic subtypes/variant discrepancies in 10.5% (n = 407), and reclassification between benign and malignant diagnoses occurred in 12.2% of patients (malignant to benign: 6.5%, n = 252; benign to malignant: 5.7%, n = 223). Discrepancies in depth of invasion resulted in upstaging in 7.7% of tumors (n = 299), including transitions from carcinoma in situ to lamina propria invasion and from lamina propria to muscularis propria invasion. Among flat lesions, approximately 12% of discrepancies involved the presence or absence of carcinoma in situ. Importantly, a subset of cases (2%) were reclassified as non-urothelial tumors (n = 77), including prostatic origin (n = 46), pure squamous cell carcinoma (n = 10), inflammatory myofibroblastic tumor (n = 4), villous adenoma (n = 4), leiomyosarcoma (n = 4), paraganglioma (n = 3), ovarian tumors (n = 3), and rare cases of angiosarcoma, breast and endometrial carcinoma (n = 1 each). Following expert review, 30% were reclassified as high-risk lesions, while 10% were reclassified as low-risk. In conclusion, these findings support using intra- or extra-departmental subspecialty consultation in diagnostically challenging cases to optimize patient management.