(UroToday.com) The Société Internationale D’Urologie (SIU) 2021 annual meeting included a master class on biomarkers in cancer and a presentation by Dr. Seth Lerner discussing molecular subtypes of bladder cancer. Dr. Lerner started by highlighting seminal work from his group that used the bladder cancer TCGA dataset to provide a comprehensive molecular characterization of muscle invasive bladder cancer.1 Among 412 muscle-invasive bladder cancer specimens, this work identified five expression subtypes including: luminal, luminal papillary, luminal infiltrated, basal squamous, and neuronal,