FAP and melanoma: Samaniegeo and colleagues identified three subsets of MSCs that contribute to regulate different steps of leukocyte tumor infiltration: CD90+ cells surrounding peritumoral vessels secrete C-C motif chemokine ligand CCL2 to recruit leukocytes at the tumor periphery, which inhibit development of malignant melanoma; intratumoral fibroblast activation protein FAP+ cells organize a stromal scaffold that contact guides further invasion among densely packed tumor cells; and CD90+FAP+ MSCs have no effects on tumor [16].