CD34 and hematologic disorder: Hematopoietic stem cell transplantation (SCT) has provided lifesaving treatment for many hematological disorders, but a significant proportion of patients who are eligible for autologous SCT fail to mobilize a sufficient number of CD34+ hematopoietic stem/progenitor cells (HSPCs), which is called “poor mobilization”, owing to various premobilization (predictive) factors such as prior treatment with stem cell toxic drugs, underlying disease, age, prior radiotherapy, and bone marrow involvement [1–3].