The chances of hematologic tumor recurrence should be very low after more than a decade of rejection after hemi-compatible transplantation. One mechanism of allogeneic hematopoietic stem cell transplantation for the treatment of malignant hematological diseases is the use of its graft-antitumor effect, which simply means that the implanted allogeneic immune/hematopoietic cells can remove the residual malignant tumor cells in the body. Hemi-compatible transplants have a greater chance and degree of rejection due to the large difference in genetic background. The rejection is caused by the implanted allogeneic immune/hematopoietic cells, and the graft-antitumor effect is also exerted by this group of cells. Although it is currently believed that the rejection reaction and the graft-antitumor effect are mediated by different subpopulations of cells in the implanted allogeneic immune/hematopoietic cells, there is an overlap between the two subpopulations of cells, i.e., a group of cells in this group that causes the deleterious rejection reaction also mediates the beneficial graft-antitumor effect. Therefore, theoretically, the heavier the rejection reaction and the longer it lasts, the lower the recurrence rate of the malignancy it treats may be, and recipients of hemiapheresis grafts with rejection lasting more than a decade should have a very low recurrence rate of their malignancy.