Clinicopathological and Cytogenetic Comparison of Patients with Acute T Lymphoblastic Leukemia and Lymphoblastic Lymphoma

Due to similar cytomorphological features and treatment strategies, T lineage lymphomas (T-LBL) and lymphoblastic leukemias (T-ALL) are usually grouped together as a single entity. Traditionally, the difference between T-LBL and T-ALL has been based on percentage of blasts found in the bone marrow (BM): >25% BM blasts and/or presence of peripheral blood (PB) blasts consistent with T-ALL. Recent studies, based on immunophenotypic, cytogenetic and molecular differences, emphasize the clinical uniqueness between T-LBL and T-ALL and argue against grouping them as a single entity.

To perform a clinicopathologic and cytogenetic comparison between patients with T-LBL and T-ALL in order to identify differences between these disease groups.

We utilized the Mayo Clinic Lymphoma database to identify consecutive adult patients (>18 years) diagnosed with T-cell leukemia and lymphoma from 1980 to 2010. The patients were sub-divided into T-LBL and T-ALL based on BM and PB blasts (absence of BM and PB blasts consistent with T-LBL). Clinicopathological and cytogenetic characteristics were retrospectively reviewed.

50 patients met the criteria for T-cell leukemia/lymphoma (29-T-ALL, 21-T-LBL). 50% of patients in each group were females with median age at diagnosis of 32 years for T-LBL and 29 years for T-ALL. Characteristics associated with a statistically significant survival difference for the cohort included: white blood cell count at diagnosis (>100,000/cmm), platelet count (<50,000/cmm), LDH (>500 U/L), presence of BM blasts and an adverse karyotype (hypodiploidy and MLL rearrangements). ECOG performance status, number of lymph node groups involved, extranodal disease, CNS involvement and constitutional symptoms had no impact on survival. Furthermore, no overall survival difference between patients with T-LBL and T-ALL was identified (figure 1).

Among patients with T-LBL, 11 (51%) patients with extranodal disease had shortened survival (p=0.02). CNS involvement was seen in 4 (19%) of T-LBL patients and 5 (17%) of T-ALL patients, and did not affect overall survival (p=0.8). 4 (19%) T-LBL patients and 1 (3%) T-ALL patient had pleural involvement at diagnosis. There were no morphologic, flow cytometric, or immunohistochemical differences noted between the two groups.

In a large study from a single institution, we confirm no survival difference between T-LBL and T-ALL, which further provides ongoing support that from a therapeutic standpoint these groups can be viewed as a single entity. However, we hope to further clarify clinical differences by performing microarray and chemokine analysis on available tissue specimens.

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No relevant conflicts of interest to declare.