PTN and neoplasm: Both MDK and PTN are closely related growth factors known for their pleiotropic effects on cell growth, differentiation, and survival through the activation of downstream signaling pathways including PI3K-AKT and MAPK/ERK.33,34 Interestingly, in Group 3 MB, the signaling was coming from several tumor clusters toward a cluster of cells expressing photoreceptor markers (Figure 3C) that also lacked CNVs (Figure 4A), therefore, resembling normal cells.