Wingless/Integrated (Wnt): A cell signaling pathway that performs several functions depending on the cell type. In bone, canonical (classical) Wnt signaling is used to direct mesenchymal stem cells to commit to an osteogenic (bone-forming) lineage, and malignancies involving bone can exploit this pathway to cause bony growths (osteogenic lesions) or “eat away” at bone (osteolytic lesions).