Migrating SCs and BCs can be distinguished morphologically, but the SC-Nxph1 and BC-Sorcs3 markers are not detected until MLIs settle and express Pvalb. Additional snRNA-Seq profiling of developing cerebella did not produce clues, as the MLI1/MLI2 trajectories diverge late following a shared Pax2+ path45. The gene discussed is NXPH1; the disease is breast cancer.