CD19 and acute lymphoblastic leukemia: Once we stained BM samples with these markers in parallel to the EuroFlow BCP-ALL MRD panel, we could clearly demonstrate that BM stromal cells can be unequivocally detected with the later panel, based on high expression of CD73 and CD81 in the absence of CD45 and other hematopoietic markers (i.e., CD19, CD66c, CD123, CD38, and CD20).