SP7 and neoplasm: Next, to confirm that expression of CD45 in the TdTOSX+ cells was not due a tight interaction between a CD45+ immune cell and TdTOSX+ mesenchymal cell, we performed CD45 immunostaining on paraffin-embedded B16-F10 tumor sections and on bone marrow single cell suspension from Osx-cre;TdT reporter mice.