CD34 and neoplasm: CM from CD105(+)/CD34(-) fibroblasts more strongly promoted migration and proliferation and increased the expression of genes associated with stemness, osteogenic differentiation, bone mineralization, and osteoclastogenesis in luminal and triple-negative human breast cancer cell lines, compared with CM from CD105(-)/CD34(-) fibroblasts.<h4>Conclusion</h4>These findings identify CD105 as a potential functional discriminator of breast CAF subpopulations and suggest that CD105(+) fibroblasts may preferentially support tumor progression and the acquisition of bone-related traits.