Acute myeloid leukemia with t(16;16) (p13;q22) showing a new CBFB-MYH11 fusion transcript associated with an atypical leukemic blasts morphology

Rare type I CBFβ/MYH11 fusion transcript in primary acute myeloid leukemia with inv(16)(p13.1q22): a case report

Inv(16)(p13.1q22) in acute myeloid leukemia (AML) is a common chromosomal abnormality. It leads to the core-binding factor ß-subunit (CBFβ)/smooth muscle myosin heavy chain 11 (MYH11) fusion gene. Different breakpoints were observed in the CBFβ gene at 16q22 and the MYH11 gene at 16p13.1. For this reason, different CBFβ/MYH11 fusion genes are generated, with more than 13 types having been reported to date. Type I CBFβ/MYH11 fusion transcripts are very rare, with only 10 cases being reported to date. This case report describes a primary AML patient with inv(16)(p13.1q22) and a rare type I CBFβ/MYH11 fusion gene. The morphological analysis did not conform to the typical M4eo. Abnormal eosinophils were less than 5%, and there was obvious dysgranulopoiesis. The patient was in hematological and genetic remission for 487 days after the initial chemotherapy cycles. However, the CBFβ/MYH11 fusion had been constantly positive. Moreover, the presence of non-type A fusions may affect its biology and clinical prognosis. Therefore, further studies on understanding its biological and prognostic significance are essential.

Hypereosinophilia: A rare presentation of acute lymphoblastic leukaemia

Acute lymphoblastic leukaemia (ALL) presenting as peripheral blood hypereosinophilia is very rare and the incidence is <1%. The characteristic feature of patients with ALL and hypereosinophilia is the absence of blasts in peripheral blood, and this might lead to misdiagnosis of ALL. It is important for clinicians and pathologists to be aware of this uncommon initial presentation of ALL to avoid delay in diagnosis. We report a 37-year-old man who presented with fever and respiratory symptoms and was found to have hypereosinophilia in peripheral blood. His bone marrow and lymph node biopsies were diagnostic of ALL.

A complex and cryptic intrachromosomal rearrangement generating the FIP1L1_PDGFRA in adult acute myeloid leukemia

Myeloid neoplasms with eosinophilia and abnormalities of the PDGFRA gene can benefit from therapy with tyrosine kinase inhibitors, therefore revealing the PDGFRA rearrangement is essential to ensure the best choice of treatment. The most common PDGFRA partner is the FIP1L1 gene, generating the oncoprotein FIP1L1/PDGFRA (F/P). In the majority of cases the F/P fusion gene originates from intrachromosomal rearrangement at band 4q12, and occasionally from chromosomal translocations. In both cases, the interstitial chromosomal deletion of a region involving the CHIC2 gene has been reported, which is cryptic by conventional karyotyping but detectable by Fluorescence In Situ Hybridization (FISH) analyses. Herein, we report an acute myeloid leukemia (AML) case presenting with eosinophilia; the F/P fusion gene originated from a new, cryptic and complex intrachromosomal rearrangement of 4q12. Classical FISH assay revealed abnormal hybridization signals, but the presence of the F/P chimaeric gene was demonstrated by molecular analysis. We performed molecular characterization of the chromosomal rearrangement and targeted Next-Generation Sequencing (NGS) analysis with a myeloid gene panel, revealing the presence of pathogenic genomic variants affecting the TET2 and ETV6 genes. These mutations were present as subclones at the disease onset and their clone size increased at relapse.

Detection of a novel CBFB-MYH11 fusion transcript in acute myeloid leukemia M1 with inv(16)(p13q22)

Acute myeloid leukemia (AML) with an inv(16)(p13q22) or t(16;16)(p13;q22) chromosomal abnormality represents one of the most common subtypes of de novo cases. These chromosomal rearrangements result in multiple CBFB-MYH11 fusion transcripts, with type-A being the most frequent. We here describe a unique case of de novo AML-M1, with inv(16)(p13q22), leading to an unusual CBFB-MYH11 fusion transcript, and der(7)t(7;11)(q31;q21). The fusion transcript involves a CBFB exon 5 with a breakpoint at nucleotide 754, an insertion of a 13-bp sequence of CBFB intron 5 at the fusion point, and the MYH11 exon 27 with a breakpoint at nucleotide 3464. To our knowledge, this CBFB-MYH11 fusion transcript has never been reported previously. The clinical characteristics of the present case are in line with previous reports suggesting that rare CBFB-MYH11 fusion transcripts lead to aberrant characteristics such as an atypical cytomorphology and additional cytogenetic abnormalities.

The predictive value of morphological findings in early diagnosis of acute myeloid leukemia with recurrent cytogenetic abnormalities

This study explores cytomorphologic features and their predictive role for early identification of acute myeloid leukemia (AML) with morphological distinctive recurrent cytogenetic abnormalities (RCA): t(15;17), t(8;21) and inv(16)/t(16;16). We retrospectively evaluated 396 de novo AML cases, diagnosed and treated at single institution, between 2013-2017. Specific cytomorphologic features suggesting distinctive AML-RCA were revealed at diagnosis in 62 (15.65%) patients, including AML with t(15;17) in 41 (66.13%), t(8;21) in 13 (20.97%) and inv(16)/t(16;16) in 8 (12.90%). Final diagnoses of AML-RCA according to WHO integrated diagnostic criteria were established in 66 (16.66%) cases, including AML with t(15;17) 40 (60.60%), t(8;21) 17 (25.76%), and inv(16)/t(16;16) 9 (13.64%). Discordance between cytomorphological and other integrated criteria was detected as missed/wrong-call in 0/1 for t(15;17), 6/2 for t(8;21) and 2/1 for inv(16)/t(16;16). The cytomorphological accuracy was 97.56% (40/41) for t(15;17), 57.89% (11/19) for t(8;21) and 70% (7/10) for inv (16)/t(16;16). Positive/negative predictive values of cytomorphological evaluation were: 97.56%/100% for t(15;17); 84.62%/88.68% for t(8;21); 87.50%/96.65% for inv(16)/t(16;16). Sensitivity/specificity were: 100%/96.15% for t(15;17); 64.10%/95.92% for t(8;21); 77.78%/98.25% for inv(16)/t(16;16). We confirmed that morphology is still a highly relevant evaluation method in diagnosing several common AML-RCAs before completing cytogenetic and molecular studies, enabling early detection, particularly of AML with t(15;17).

Most Myeloid Neoplasms With Deletion of Chromosome 16q Are Distinct From Acute Myeloid Leukemia With Inv(16)(p13.1q22): A Bone Marrow Pathology Group Multicenter Study

OBJECTIVES

Isolated deletion of the long arm of chromosome 16 (del(16q)) is rare in myeloid neoplasms (MNs) and was historically considered a variant of inv(16)(p13.1q22) (inv(16)), a subtype of acute myeloid leukemia (AML) associated with CBFB-MYH11 rearrangement and favorable prognosis. This study aims to determine clinicopathologic characteristics of patients with isolated del(16q) in MNs in comparison to AMLs with isolated inv(16).

METHODS

Clinicopathologic features were retrospectively reviewed in 18 MNs with del(16q) and 34 AMLs with inv(16) patients from seven institutions.

RESULTS

MNs with del(16q) occurred in elderly patients, often as secondary MNs. Blood monocytes and marrow eosinophils were lower in del(16q) than inv(16). Deletion of CBFB but not CBFB-MYH11 rearrangement was confirmed by fluorescence in situ hybridization or reverse transcription polymerase chain reaction in 14 of 14 del(16q) patients. The median overall survival was shorter in del(16q) than in inv(16) patients (12 vs 94 months, log rank P = .0002).

CONCLUSIONS

Myeloid neoplasms with isolated del(16q) with deletion of the CBFB but lacking CBFB-MYH11 rearrangement should not be considered a variant of the AML-defining inv(16).

Fusion genes in malignant neoplastic disorders of haematopoietic system

OBJECTIVES

The new World Health Organization's (WHO) classification of haematopoietic and lymphoid tissue neoplasms incorporating the recurrent fusion genes as the defining criteria for different haematopoietic malignant phenotypes is reviewed. The recurrent fusion genes incorporated in the new WHO's classification and other chromosomal rearrangements of haematopoietic and lymphoid tissue neoplasms are reviewed.

METHODOLOGY

Cytokines and transcription factors in haematopoiesis and leukaemic mechanisms are described. Genetic features and clinical implications due to the encoded chimeric neoproteins causing malignant haematopoietic disorders are reviewed.

RESULTS AND DISCUSSION

Multiple translocation partner genes are well known for leukaemia such as MYC, MLL, RARA, ALK, and RUNX1. With the advent of more sophisticated diagnostic tools and bioinformatics algorithms, an exponential growth in fusion genes discoveries is likely to increase.

CONCLUSION

Demonstration of fusion genes and their specific translocation breakpoints in malignant haematological disorders are crucial for understanding the molecular pathogenesis and clinical phenotype of cancer, determining prognostic indexes and therapeutic responses, and monitoring residual disease and relapse status.

Hypereosinophilia in Acute Lymphoblastic Leukemia: Two Cases with Review of Literature

Eosinophilia is rare in acute leukemia at presentation. Discrete reports and case studies in recent years have created significant interest in the field of "Acute leukemia with eosinophilia". We herein present two cases of eosinophilia in association with acute lymphoblastic leukemia with brief review of literature in this field. First case is about 21-year-old female who presented with mediastinal mass along with leukocytosis and hypereosinophilia. On evaluation, she was found to have T cell acute lymphoblastic leukemia. After ruling out benign causes of eosinophilia, she was treated with modified BFM-90 protocol. Her eosinophilia resolved after 4 weeks of induction therapy. Second case is about 32-year-old male who was diagnosed as a case of mixed phenotype leukemia (B cell/myeloid type) along with severe eosinophilia. His hypereosinophilia finally resolved by week 16 of modified BFM-90 protocol. Diagnosing ALL is challenging when eosinophilia is the initial presentation. These two cases emphasize on the importance of considering ALL amongst one of the etiological causes of eosinophilia as delay in diagnosis endangers patient's life at risk. Also eosinophilia per se is an independent poor risk factor, hence prompt diagnosis and early treatment is the key in all such cases.