CD34 and neoplasm: In addition to subtype-specific tumor signatures, this study uncovered a stromal cell expression pattern in MBCs, with the most prominent being downregulated expression of mesenchymal stem cell proteins (CD59, CD248), macrophages (CD209), immune cells (CD8A), hematopoietic stem/endothelial progenitors/macrophages (CD34, CD36, CDH5), a recently discovered mammary stem cell marker (CDH5)35, and detected evidence of endothelial-to-mesenchymal transition (EndMT; CDH5loIGFBP4loCD34lo).