This protocol aims to create a tissue bank of breast tumors obtained at the time of diagnosis for the identification of biomarkers for diagnosis, prognostication, and prediction of treatment response in breast cancer. While tissue banks now exist in major hospitals in Singapore to collect tumor specimens at the time of surgery, specimens collected at surgery from patients who had undergone pre-operative treatment represent a post-treatment sample and not a baseline, untreated sample. Such samples are intrinsically different from untreated samples, and have to be analyzed separately from untreated samples. However, they remain valuable samples, particularly if a pre-treatment sample has been obtained, providing paired pre- and post-treatment samples, which could provide valuable information on treatment-related tumor biomarker changes. A tissue bank comprising of samples collected during the diagnostic core biopsy thus represents a valuable supplement to existing tissue banks.