Plasmacytoid urothelial carcinoma of the bladder: MRI features and their association with survival.

Objectives: Plasmacytoid urothelial carcinomas (PUC) of the bladder are rare variants known for diffuse and infiltrative spread, however their magnetic resonance imaging (MRI) features are not well established. We aimed to evaluate MRI features of PUC of the bladder and their association with survival.

Methods And Materials: This retrospective single-center study included 41 patients with pathologically-proven bladder PUC of the bladder that underwent pre-treatment MRI between January 2000 and March 2020. Two radiologists reviewed MRIs independently followed by consensus with a third radiologist. On MRI, tumor extent, size, Vesical Imaging-Reporting and Data System (VI-RADS) scores (≥4, muscle-invasive; 5, extravesical extension [EVE]), pelvic peritoneal spread (PPS), hydronephrosis, pelvic adenopathy and clinicopathological factors of age, gender, pathological stage, and treatment type were extracted. Kaplan-Meier curves and Cox proportional-hazards models were used to evaluate association with survival.

Results: Thirty-two men and 9 women (median age 70 years, IQR 64-76) were included. Most were muscle-invasive (n = 30 [73.2%]). On MRI, most tumors were diffuse (n = 28 [68.3%]), >5 cm (n = 30 [73.2%]), VI-RADS 4 to 5 (n = 36 [87.8%]) with features of EVE and (n = 31 [75.6%]) and PPS (n = 25 [61.0%]). Variables associated with survival were: Larger tumors (>5 cm; hazard ratio [HR] = 5.0; 95% confidence interval [CI] 1.6-15.5; P < 0.01), diffuse extent (HR = 4.0; 95% CI 1.4-11.2; P = 0.01), EVE (HR = 4.5; 95% CI 1.5-13.6; P < 0.01), PPS (HR = 3.0; 95% CI 1.2-7.4; P = 0.01), hydronephrosis (HR = 13.7; 95% CI 3.1-60.9; P < 0.01), pathologic stage (≥pT3 vs. pT1; HR = 5.6; 95% CI 1.3-22.0; P = 0.02), and margin positivity (HR = 4.4 [95% CI 1.2-16.4], P = 0.03).

Conclusion: PUCs of the bladder are commonly large, diffuse VI-RADS score 4 to 5 tumors with MRI features of EVE and PPS. These features and pathological stage were associated with survival.