CXCR4 and hematopoietic and lymphoid system neoplasm: CXCR4 antagonist plerixafor has been approved as a stem cell mobilization agent for peripheral stem cell collection for the autologous peripheral stem cell transplantation [152], and 68Ga-pentixafor has been used for CXCR4-directed PET imaging in patients with hematologic neoplasms and malignant solid tumors [153,154].