Figure 1

Changes in tissue morphology along the axis of tissue sections. Overlay of the distributions of viable cancer marker ion (m/z 391.25 from DESI-MS imaging) from two serial sections of human breast cancer tumour ~75 μm apart. Images were overlaid using optimized rigid body alignment, as judged by largest circumference of aligned regions on outside border of the tissue. The analysis reveals a significant (1–1.5 mm) mismatch of internal borders between consecutive viable cancer subregions. The DESI-MS image of the marker shown is published previously33 and is reproduced here for the clarity of our discussion regarding how tissue morphology in this tumour model changed over the 75 μm axial distance.