ABSTRACT
T-acute lymphoblastic leukemia (T-ALL) is a neoplasm of immature T-cell precursors or T lymphoblasts that accounts for approximately 20–25% of patients with ALL (15% of childhood and 25% of adult ALL) [1]. T-ALL has clinical, immunologic, cytogenetic, and molecular features that are distinct from those with B-ALL [2–9]. T-ALL is closely related to T-lymphoblastic lymphoma (T-LBL), but they differ in clinical presentation and site of relapse: T-lymphoblastic lymphoma usually presents as a mediastinal mass or lymphadenopathy whereas T-ALL patients present with predominantly bone marrow (BM) and blood disease. T-ALL/LBL occurs more often in male than female patients (at ratio ∼6:1) and involves BM and blood, mediastinum and, less commonly, lymph nodes, skin, gonads, and central nervous system (CNS) [10–16]. Mediastinal involvement and adenopathy are more common in younger patients than in patients older than 60 years. Patients with <25% of BM involvement are classified as T-LBL while patients with 25% or more BM blasts are diagnosed with T-ALL [16]. With intensive chemotherapy, cure rates for T-ALL/LBL approach 80% [17,18].
