Although both LNM and principal tumor cells expressed pigmentation genes at low levels, there was scant pigment visible on the surface of black Braf CA/+PtenΔ/+ tumors (Fig. 1c), a finding also reported by others57, which motivated us to examine whether gene expression of any of the cells in these tumors aligned with the Mitf-high pigmentation signature that has been identified in other mouse and human melanomas. The gene discussed is MITF; the disease is melanoma.