DKK1 and neoplasm: DKK1 staining was observed in some cancer epithelial cells, identified by the co-expression with a pan-cytokeratin (PanCK) marker, and in PDGRFa+ and aSMA+ stromal populations in all tumor types (Fig. 2D–F), while it was not detected in the terminal duct lobular unit of normal breast tissue (Supp Fig. 2E).