The graft versus tumor (GVT) effect, also known as graft versus malignancy effect, is a significant phenomenon observed in the context of hematopoietic stem cell transplantation (HSCT). It refers to the beneficial role played by donor immune cells in identifying and eliminating malignant cells in the recipient's body. This effect is closely related to the graft versus host disease (GVHD), where donor immune cells attack the recipient's non-malignant tissues.