CD4 and cancer: Tfh cells were identified by expression of CD4, CXCL13 and BCL6 then categorized based on their spatial location within the tissue, in two analogous ways: (i) by proximity to B cells (Extended Figure 5B) and (ii) into cancer-adjacent Tfh cells or Tfh cells in lymph-rich regions based on whether cancer cells or B cells were more common within a 200 μm radius (Figure 5B–C).