Chronic myeloid leukemia presenting in lymphoblastic crisis, a differential diagnosis with Philadelphia-positive B-lymphoblastic leukemia

Blast phase of chronic myeloid leukemia presenting as early T-cell precursor acute lymphoblastic leukemia

OBJECTIVES

The blasts in most cases of chronic myeloid leukemia blast phase (CML-BP) have a myeloid or precursor-B immunophenotype, with only a small subset having T-cell or natural killer-cell lineage. Patients with CML-BP having early T-cell precursor acute lymphoblastic leukemia (ETP-ALL) are extremely rare.

METHODS

We report the clinicopathologic, immunophenotypic, and molecular genetic features and outcome of 3 patients with CML-BP who had ETP-ALL, with a review of the literature.

RESULTS

Only patient 1 had a history of chronic myeloid leukemia chronic phase. Fluorescence in situ hybridization revealed BCR::ABL1 rearrangement in cells with round nuclei (blasts) and cells with segmented nuclei (neutrophils) in cases 2 and 3, supporting a diagnosis of CML-BP rather than de novo Ph+ ETP-ALL. The blasts were positive for cytoplasmic CD3, CD7, CD33, and CD117; were negative for CD1a and CD8; and had dim CD5 expression in 2 cases. Next-generation sequencing showed a TET2 mutation in case 1 and BCOR, RUNX1, and STAG2 mutations in case 3. All patients received chemotherapy and tyrosine kinase inhibitors. Patients 2 and 3 died 33 days and 39 days, respectively, after diagnosis. Patient 1 received stem cell transplantation and was alive 14 months after blast phase.

CONCLUSIONS

Patients with CML-BP may have ETP-ALL. These patients usually have an aggressive clinical course, requiring intensive therapy, and may benefit from stem cell transplantation.

International Consensus Classification of acute lymphoblastic leukemia/lymphoma

The updated International Consensus Classification (ICC) of B-acute lymphoblastic leukemia (B-ALL) and T-acute lymphoblastic leukemia (T-ALL) includes both revisions to subtypes previously outlined in the 2016 WHO classification and several newly described entities. The ICC classification incorporates recent clinical, cytogenetic, and molecular data, with a particular emphasis on whole transcriptome analysis and gene expression (GEX) clustering studies. B-ALL classification is modified to further subclassify BCR::ABL1-positive B-ALL and hypodiploid B-ALL. Additionally, nine new categories of B-ALL are defined, including seven that contain distinguishing gene rearrangements, as well as two new categories that are characterized by a specific single gene mutation. Four provisional entities are also included in the updated B-ALL classification, although definitive identification of these subtypes requires GEX studies. T-ALL classification is also updated to incorporate BCL11B-activating rearrangements into early T-precursor (ETP) ALL taxonomy. Additionally, eight new provisional entities are added to the T-ALL subclassification. The clinical implications of the new entities are discussed, as are practical approaches to the use of different technologies in diagnosis. The enhanced specificity of the new classification will allow for improved risk stratification and optimized treatment plans for patients with ALL.

International Consensus Classification of Myeloid Neoplasms and Acute Leukemias: integrating morphologic, clinical, and genomic data

The classification of myeloid neoplasms and acute leukemias was last updated in 2016 within a collaboration between the World Health Organization (WHO), the Society for Hematopathology, and the European Association for Haematopathology. This collaboration was primarily based on input from a clinical advisory committees (CACs) composed of pathologists, hematologists, oncologists, geneticists, and bioinformaticians from around the world. The recent advances in our understanding of the biology of hematologic malignancies, the experience with the use of the 2016 WHO classification in clinical practice, and the results of clinical trials have indicated the need for further revising and updating the classification. As a continuation of this CAC-based process, the authors, a group with expertise in the clinical, pathologic, and genetic aspects of these disorders, developed the International Consensus Classification (ICC) of myeloid neoplasms and acute leukemias. Using a multiparameter approach, the main objective of the consensus process was the definition of real disease entities, including the introduction of new entities and refined criteria for existing diagnostic categories, based on accumulated data. The ICC is aimed at facilitating diagnosis and prognostication of these neoplasms, improving treatment of affected patients, and allowing the design of innovative clinical trials.

Unusual B-Lymphoid Blastic Crisis as Initial Presentation of Chronic Myeloid Leukemia Imposes Diagnostic Challenges

Chronic myeloid leukemia (CML) is a clonal hematopoietic stem cell disorder, characterized by reciprocal translocation t(9,22) (q34; q11), leading to increased myeloid proliferation. Most cases are diagnosed in the chronic phase (CP). However, a minority of cases can be present in the blastic phase (BP). In most patients with CML-BP, the blasts have a myeloid phenotype, however, in 20–30% of cases, the blasts have a lymphoid phenotype, mostly a B-cell phenotype. It is challenging to differentiate CML B-lymphoblastic phase (CML-BLP) from Ph + primary B-acute lymphoblastic leukemia (B-ALL) especially when the CML-BLP is the initial presentation of the disease, which is uncommon. We report here an unusual case of CML-BLP as an initial presentation of the disease without typical CML morphological findings. This case demonstrates diagnostic challenges and emphasizes the importance of an integrated approach using morphology, multiparametric flow cytometry, cytogenetic studies, and molecular studies to render an accurate diagnosis.

Outcome of patients with chronic myeloid leukemia in lymphoid blastic phase and Philadelphia chromosome-positive acute lymphoblastic leukemia treated with hyper-CVAD and dasatinib

BACKGROUND

Dasatinib monotherapy has demonstrated modest clinical activity in chronic myeloid leukemia in lymphoid blastic phase (CML-LBP). The outcome of Philadelphia chromosome (Ph)-positive acute lymphoblastic leukemia (ALL) has dramatically improved with hyperfractionated cyclophosphamide, vincristine sulfate, doxorubicin hydrochloride, and dexamethasone (hyper-CVAD) in combination with tyrosine kinase inhibitors (TKIs).

METHODS

The authors reviewed 85 patients (23 with CML-LBP and 62 with newly diagnosed Ph-positive ALL) who received hyper-CVAD plus dasatinib.

RESULTS

In the CML-LBP cohort, 19 had prior chronic myeloid leukemia as chronic phase (n = 17; 74%), accelerated phase (n = 1; 4%), or myeloid blastic phase (n = 1; 4%); 4 (17%) presented with de novo CML-LBP. The BCR-ABL1 transcript was p210 in 22 patients (96%) and p190 in 1 patient (4%). In the Ph-positive ALL cohort, p210 and p190 transcripts were detected in 13 patients (21%) and 48 patients (77%), respectively. Patients with CML-LBP were less likely to achieve deep molecular remission than patients with Ph-positive ALL: the major molecular response (MMR) rates were 70% and 95%, respectively (P = .007), and the complete molecular response (CMR) rates were 55% and 74%, respectively (P = .16). Survival outcomes were similar for CML-LBP and Ph-positive ALL: the 5-year overall survival (OS) rates were 59% and 48%, respectively (P = .97). Allogeneic stem cell transplantation was associated with a better outcome in CML-LBP (5-year OS rate, 88% vs 57%; P = .04). In Ph-positive ALL, the outcome was driven by deeper molecular remission: the 5-year OS rates were 63% and 25% with CMR and MMR, respectively (P = .002).

CONCLUSIONS

The outcome of CML-LBP has improved with hyper-CVAD plus dasatinib therapy with survival comparable to that of Ph-positive ALL. Further improvement may be achieved with the use of novel TKIs and targeted agents.