CD99 and acute lymphoblastic leukemia: The cluster of differentiation 99 (CD99) is crucial for normal T cell development [9,10], and its dysregulation in T lymphoblastic leukemia/lymphoma (T-ALL/T-LBL) can disrupt essential signaling cascades, leading to impaired differentiation, immune evasion, and, ultimately, the malignant transformation of T cells [11].