Molecular Profiling of Urothelial Bladder Cancer: Bridging Tumor Biology and Clinical Decision-making.

Bladder cancer ranks among the most common malignancies worldwide, with urothelial carcinoma as the predominant histological type. Its development from normal urothelium to non-muscle-invasive bladder cancer (NMIBC) or muscle-invasive bladder cancer (MIBC) is driven by complex molecular events, including chromosomal aberrations, somatic mutations, and epigenetic dysregulation. Advances in next-generation sequencing (NGS) and transcriptomic profiling have transformed the understanding of urothelial tumor biology and opened new perspectives for precision oncology. To provide an updated synthesis of molecular profiling in urothelial bladder cancer across disease stages and to discuss its diagnostic, prognostic, and therapeutic relevance. We conducted a targeted narrative review based on a structured PubMed search of studies published between January 2000 and February 2026 using the keywords "genomic," "epigenetic," "transcriptomic," and "urothelial bladder cancer." Eligible publications included original research articles, reviews, and meta-analyses in English. Evidence was synthesized across NMIBC, MIBC, and metastatic disease, focusing on molecular alterations and their clinical relevance. Both NMIBC and MIBC present frequent TERT promoter mutations. NMIBC is further characterized by frequent FGFR3 and PIK3CA mutations, loss of chromosome 9, and widespread chromatin-remodeling gene alterations. MIBC displays high genomic instability, with recurrent mutations in TP53, RB1, and chromatin modifiers, as well as frequent alterations in the RTK/RAS/PI3K pathway. Consensus transcriptomic classifications identify reproducible molecular subtypes (luminal, basal/squamous, stroma rich, and neuroendocrine like), each with distinct biological and clinical behaviors. In metastatic disease, NGS and whole-exome analyses reveal strong concordance with localized tumors, with frequent TP53, ARID1A, KMT2D, RB1, and FGFR3 alterations and APOBEC mutational signatures. Transcriptomic profiling shows subtype heterogeneity and therapy-induced remodeling. Clinically, only FGFR3 alterations currently guide therapy, with erdafitinib approved by the US Food and Drug Administration and the European Medicines Agency for FGFR3-altered metastatic disease. Beyond tumor testing, circulating tumor DNA assays show promise for molecular residual disease detection and adjuvant treatment stratification. Molecular profiling has deepened the understanding of bladder cancer biology and identified potential biomarkers for diagnosis, prognosis, and treatment. However, clinical implementation remains limited, and prospective biomarker-driven trials are needed to establish the role of genomic and transcriptomic alterations in therapeutic decision-making.