HAEM5:B-lymphoblastic leukaemia/lymphoma with BCR::ABL1-like features: Difference between revisions

The presenting symptoms are similar to those of other ALL patients, with the exception of potentially higher white blood cell counts<ref name=":2">Borowitz MJ, et al., (2017). B-lymphoblastic leukaemia/lymphoma with recurrent genetic abnormalities, in World Health Organization Classification of Tumours of Haematopoietic and Lymphoid Tissues, Revised 4th edition. Swerdlow SH, Campo E, Harris NL, Jaffe ES, Pileri SA, Stein H, Thiele J, Arber DA, Hasserjian RP, Le Beau MM, Orazi A, and Siebert R, Editors. IARC Press: Lyon, France, p208.</ref>.

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==Sites of Involvement==

Blasts are typically CD19, TdT, and CD10-positive. By flow cytometry, a subset of cases with CRLF2 translocations show very high levels of surface protein expression<ref name=":2" />.

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==Chromosomal Rearrangements (Gene Fusions)==

Tyrosine kinase-type translocations are common and involve ''ABL1'' and other kinases (such as ''ABL2'', ''EPOR'', ''JAK2'', ''PDGFRB'', and ''CSF1R''); more than 30 gene partners have been described. Frequently reported examples include ''IGH''–''EPOR'' of the t(14;19)(q32;p13)/ins(14;19)(q32;p13), ''EBF1''–''PDGFRB'' of the del(5)(q32q33.3), ''NUP214''–''ABL1'' of the t(9;9)(q34;q34)/del(9)(q34q34), and ''ETV6''–''ABL1'' of the t(9;12)(q34;p13). Other notable fusions are ''BCR''–''JAK2'', ''PAX5''–''JAK2'', ''STRN3''–''JAK2'', ''RANBP2''–''ABL1'', ''RCSD1''–''ABL1'', and ''MEF2D''–''CSF1R''<ref>Heim S & Mitelman F. Cancer Cytogenetics: Chromosomal and Molecular Genetic Aberrations of Tumor Cells. John Wiley & Sons, Incorporated: Chichester, United Kingdom. 2015.</ref>.

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* Individual Region Genomic Gain/Loss/LOH

* Characteristic Chromosomal Patterns

*Diagnosis:  Definitive diagnosis is based on two major gene expression signatures (DCOG/Erasmus MC and COG/St. Jude).

**However, given the high incidence of fusions involving ''JAK2'', ''ABL1'', ''ABL2'', and other tyrosine kinases, tyrosine kinase inhibitors and JAK inhibitors are now being trialed clinically<ref name=":4" /><ref>{{Cite journal|last=Tasian|first=Sarah K.|last2=Doral|first2=Michelle Y.|last3=Borowitz|first3=Michael J.|last4=Wood|first4=Brent L.|last5=Chen|first5=I.-Ming|last6=Harvey|first6=Richard C.|last7=Gastier-Foster|first7=Julie M.|last8=Willman|first8=Cheryl L.|last9=Hunger|first9=Stephen P.|date=2012|title=Aberrant STAT5 and PI3K/mTOR pathway signaling occurs in human CRLF2-rearranged B-precursor acute lymphoblastic leukemia|url=https://www.ncbi.nlm.nih.gov/pubmed/22685175|journal=Blood|volume=120|issue=4|pages=833–842|doi=10.1182/blood-2011-12-389932|issn=1528-0020|pmc=3412346|pmid=22685175}}</ref><ref>{{Cite journal|last=Iacobucci|first=Ilaria|last2=Li|first2=Yongjin|last3=Roberts|first3=Kathryn G.|last4=Dobson|first4=Stephanie M.|last5=Kim|first5=Jaeseung C.|last6=Payne-Turner|first6=Debbie|last7=Harvey|first7=Richard C.|last8=Valentine|first8=Marcus|last9=McCastlain|first9=Kelly|date=2016|title=Truncating Erythropoietin Receptor Rearrangements in Acute Lymphoblastic Leukemia|url=https://www.ncbi.nlm.nih.gov/pubmed/26859458|journal=Cancer Cell|volume=29|issue=2|pages=186–200|doi=10.1016/j.ccell.2015.12.013|issn=1878-3686|pmc=4750652|pmid=26859458}}</ref>.

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==Individual Region Genomic Gain / Loss / LOH==

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Monoallelic (often partial) deletion of the IKAROS transcription factor, encoded by ''IKZF1'', is one of the most frequently observed genetic abnormalities in BCR-ABL1-like B-ALL, although this finding is not specific and not included in the definition<ref name=":3" />.  

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==Characteristic Chromosomal Patterns==

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Approximately half of cases demonstrate rearrangements resulting in overexpression of CRLF2<ref name=":7" />. These rearrangements are the result of either translocation of immunoglobin heavy chain enhance locus into ''CRLF2'' (''IGH''-''CRLF2''—more commonly seen in adults) or through a cryptic deletion on chromosome X/Y involving the PAR1 psuedoautosomal region, resulting in fusion of ''CRLF2'' to ''P2RY8'' (more commonly seen in children). Very rare alternative translocations involving ''CRLF2'' have also been observed.

[[File:FISH 1.jpg|thumb|none]]

(Images courtesy of Fabiola Quintero-Rivera, MD)

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==Gene Mutations (SNV / INDEL)==

In addition to gene translocations, gain-of-function mutations in ''CRLF2'' itself or in its partner gene, ''IL7RA'', have been seen<ref name=":8">Quesada A, Reynolds M, Jorgensen JL, et al. Cytokine receptor-like factor 2 (CRLF2) expression in precursor B-lymphoblastic leukemia. International Clinical Cytometry Society e-Newsletter. 2014;5(1).</ref>.  Alternative alterations activating kinase signaling occur, including activating mutations of ''FLT3'', as well as focal deletions of ''SH2B3'' (also known as ''LNK'')<ref>Tosi S & Reid AG. The Genetic Basis of Haematological Cancers. John Wiley & Sons, Incorporated: Chichester, United Kingdom: 2016.</ref>.

Herold et al. in 2017 reported a wide variety of molecular alterations in BCR-ABL1-like B-ALL, which was shown to have statistically significant associations with alterations of ''IKZF1'', ''CRLF2'', ''JAK2'', ''BTG1'', and high ''CRLF2'' expression<ref name=":5" />.

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==Epigenomic Alterations==

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*IKAROS transcription factor:  Deletion of ''IKZF1'' results in activation of ''EBF1'', ''MSH2'', and ''MCL1'', leading to B-cell leukemogenesis<ref>{{Cite journal|last=van der Veer|first=Arian|last2=Waanders|first2=Esmé|last3=Pieters|first3=Rob|last4=Willemse|first4=Marieke E.|last5=Van Reijmersdal|first5=Simon V.|last6=Russell|first6=Lisa J.|last7=Harrison|first7=Christine J.|last8=Evans|first8=William E.|last9=van der Velden|first9=Vincent H. J.|date=2013|title=Independent prognostic value of BCR-ABL1-like signature and IKZF1 deletion, but not high CRLF2 expression, in children with B-cell precursor ALL|url=https://www.ncbi.nlm.nih.gov/pubmed/23974192|journal=Blood|volume=122|issue=15|pages=2622–2629|doi=10.1182/blood-2012-10-462358|issn=1528-0020|pmc=3795461|pmid=23974192}}</ref>.

*Dysregulation of several tyrosine kinase signaling pathways (involving ''ABL1'', ''ABL2'', ''PDGFRB'', ''CSF1'', etc.) results in B-cell progenitor proliferation.

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==Genetic Diagnostic Testing Methods==