Bladder cancer is a biologically and clinically heterogeneous disease. Traditional classification systems, based on pathologic grade, stage and clinical prognosis fail to fully explain how tumors with similar pathology exhibit diverse biological behavior. The introduction of transcriptomics technology has allowed us to catalog all of the mRNA expression patterns and DNA alterations in a given tumor thus expanding our understanding of human cancers. Molecular subtype profiling was attempted only recently in bladder cancer, with the earliest attempts dating back to 2010. Several different molecular classification systems have emerged since. Some of these systems address early bladder cancer, while others focus exclusively on the life-threatening muscle invasive tumors. These molecular subtypes have distinct morphological and clinical characteristics with different therapeutic and prognostic implications, particularly in the era of targeted therapies and immunotherapy. However, molecular subtyping is not without its limitations. Despite the rapidly expanding evidence for important clinical implications, much work is still needed to establish the utility (or lack thereof) of molecular subtyping, and its application in daily practice.
Part of the book: Modern Approach to Diagnosis and Treatment of Bladder Cancer