ROBO4 and leukemia: Some studies have reported that its expression is associated with a favorable prognosis (33), while others have suggested that CD34 expression correlates with poor clinical outcome, and CD38-negative CD34-positive leukemic cells demonstrate enhanced leukemia-initiating capacity and exhibit stem-like features, including a quiescent phenotype and increased expression of adhesion-related molecules such as CD44, CXCR4, integrins, as well as the growth guidance receptor ROBO4 (35).