Fig. 1: Workflow for multicenter study of clinical samples.

Human breast tissue was obtained from patients who received surgical treatment for breast cancer at the following sites: Imperial College London (C1), Maastricht University (C3) and Queen’s University (C4). Tissue was analyzed by REIMS and validated by histopathologists. Quality control material including two batches of single-source pork liver and meat homogenate (National Institute of Standards and Technology (NIST), Standard reference material 1546a) was analyzed at all four centres including Waters Research Center (C2) to compare method performance.