A stacking ensemble system for identifying the presence of histological variants in bladder carcinoma: a multicenter study - Peng, Canjie; He, Quanhao; Lv, Fajin; Jiang, Qing; Chen, Yong; Wei, Zongjie; Xv, Yingjie; Liao, Fangtong; Xiao, Mingzhao (Frontiers in Oncology, 2025)