APC and neoplasm: Normal-looking crypts expressing Ly6a (Sca1) at the tumor boundary did not express detectable transcripts of Myc, or Notum, which is a specific marker of Apc−/− cells (Figs 6E and S7), suggesting that these cells are at a growth disadvantage relative to the Myc-expressing tumor cells (Johnston, 2014; Di Giacomo et al, 2017).