MRI–HISTOPATHOLOGY CONCORDANCE AND PATTERNS OF STAGING DISCREPANCY IN BLADDER CANCER: A SINGLE-CENTER STUDY

Abstract

Background: MRI may identify muscularis propria invasion in bladder cancer, but accuracy at the muscle-invasion threshold does not necessarily imply agreement across individual pathological T stages. We assessed stage-specific concordance and the direction of MRI staging discrepancies. Methods: We analyzed MRI and histopathological T-stage classifications recorded for 60 patients with bladder cancer evaluated at a single tertiary center in Karachi, Pakistan, between April and November 2019. Pelvic MRI was performed using a 1.5-T scanner. Exact T-stage agreement, understaging, overstaging and unweighted Cohen’s kappa were determined using the recorded seven-category staging matrix. Sensitivity, specificity, predictive values and accuracy for muscle-invasive (≥T2) versus non-muscle-invasive (≤T1) disease were calculated with 95% Wilson confidence intervals. Results: Of 60 patients, 52 (86.7%) were male; mean age was 47.21 ± 14.82 years. Exact MRI–histopathology agreement was observed in 46 patients (76.7%; 95% CI, 64.6–85.6%), whereas MRI understaged 10 (16.7%) and overstaged four (6.7%). Unweighted kappa was 0.723. For detecting muscle invasion, MRI had 92.5% sensitivity (49/53), 71.4% specificity (5/7), 96.1% positive predictive value (49/51), 55.6% negative predictive value (5/9) and 90.0% accuracy (54/60). Four of the 14 staging discrepancies crossed the T1–T2 boundary in the direction of understaging. Conclusion: Conventional MRI achieved high overall accuracy at the muscle-invasion threshold but lower concordance for exact T-stage assignment. Understaging was more frequent than overstaging, highlighting the need to interpret MRI together with pathological and clinical findings. These findings reflect a small, predominantly muscle-invasive, single-center cohort.