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Year : 2014  |  Volume : 57  |  Issue : 1  |  Page : 78-80
Your dilemma, my identity: Unusual immunogenetic profiles of pediatric B cell acute lymphoblastic leukemia


1 Department of Hematopathology, AmPath, American Oncology Institute and Citizens Hospital, Hyderabad, Andhra Pradesh, India
2 Department of Medical Oncology, Omega Hospital, Hyderabad, Andhra Pradesh, India

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Date of Web Publication17-Apr-2014
 

   Abstract 

B-cell acute lymphoblastic leukemia (B-ALL) is characterized by CD19 expression, which is one of the most important prerequisites, along with expression of CD10, CD22 and/or CD79a. Rearrangements involving MLL gene are seen in CD10 B-ALL (pro-B cell origin) and t(9;11)(p21;q23) is most commonly reported in acute myeloid leukemia (AML), where it is known to carry very good prognosis in pediatric AMLs and rarely in acute lymphoblastic leukemia (ALL). We report a case of CD10 + , CD19 pediatric ALL with rearrangements of MLL gene as a result of t(9;11)(p21;q23), thus conferring a very poor prognosis. The case emphasizes use of comprehensive panel of antibodies for flow cytometric immunophenotyping and cytogenetic correlation for correct diagnosis and prognostication.

Keywords: Acute lymphoblastic leukemia, CD19, MLL gene, t(9;11)(p21;q23)

How to cite this article:
Gupta A, Goyal M, Nidamanuri KR, Dattatreya PS. Your dilemma, my identity: Unusual immunogenetic profiles of pediatric B cell acute lymphoblastic leukemia. Indian J Pathol Microbiol 2014;57:78-80

How to cite this URL:
Gupta A, Goyal M, Nidamanuri KR, Dattatreya PS. Your dilemma, my identity: Unusual immunogenetic profiles of pediatric B cell acute lymphoblastic leukemia. Indian J Pathol Microbiol [serial online] 2014 [cited 2019 Dec 14];57:78-80. Available from: http://www.ijpmonline.org/text.asp?2014/57/1/78/130904



   Introduction Top


CD19, a 95 kD transmembrane glycoprotein of immunoglobulin (Ig) super family, is encoded by the 7.41 kilobase CD19 gene located on the short arm of chromosome 16, 16p11.2. [1] Expression of CD19 on blasts is considered as the most reliable marker for assigning them to the B cell lineage. [2] Loss of CD19 in B cell acute lymphoblastic leukemia (B-ALL) has previously been reported in a couple of instances, before World Health Organization classification of tumors of hematopoietic and lymphoid tissues, 2008 came into practice. [3] We report an unusual case of CD19 pediatric B-ALL with expression of CD10 and unusual cytogenetic profile.


   Case Report Top


This is a case report of a 2-year-old child who presented with a history of fever, splenomegaly, cervical and bilateral axillary lymphadenopathy. Initial peripheral blood (PB) examination revealed hemoglobin of 7.7 gm/dL with total leucocyte count of 9.47 × 10 9 /L and a platelet count of 46 × 10 9 /L with 66% circulating blasts. The blasts were small to medium in size with scant cytoplasm, round nuclei, open chromatin and inconspicuous nucleoli which on cytochemistry were negative for myeloperoxidase. Flow cytometric (FCM) immunophenotyping performed on the PB showed the gated cells in the blast region to be positive for CD34, CD38, TdT, CD10, CD79a and CD22. The blasts were negative repeatedly for CD19 (APC, Allophycocyanin, BD Sciences, USA, clone SJ25C1) which was reconfirmed by using another CD19 antibody labeled with PE-Cy7 (Beckman Coulter Inc., France, clone J3-119). These were also negative for myeloperoxidase, cytoplasmic CD3, other myelomonocytic and T-cell specific markers [Figure 1]. Hence, a final diagnosis of B-ALL was rendered.
Figure 1: The immunoprofile of the blasts (painted red) shows positivity for CD34, CD10, CD22, CD79a and TdT and are negative for CD19 (APC and PE-Cy7), CD20, myeloperoxidase and cytoplasmic CD3. B and T-lymphocytes are painted blue and green respectively

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Cytogenetic analysis of unstimulated PB cultures showed the presence of a neoplastic clone characterized by t(3;12)(p21;p12) in all the 20 metaphases [Figure 2]. The clone evolved further with development of a sub-clone harboring t (9;11)(p21;q23) in 4 metaphases involving the MLL gene which was confirmed by fluorescence in situ hybridization (FISH) using MLL break apart probe (Vysis, Abbott) [Figure 3]. Induction chemotherapy was initiated using BFM protocol. The 29 th day bone marrow showed complete morphological remission. However, minimal residual disease was positive by FCM.
Figure 2: Karyotype showing t(3;12)(p21;p12) (marked by blue arrows) and t(9;11)(p21;q23) (marked by the red arrows)

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Figure 3: Fluorescence in situ hybridization using break-apart probe for MLL gene (Vysis, Abbott) showing one intact yellow fusion signal indicating normal MLL gene and distinct broken apart red and green signals indicating MLL gene involvement

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   Discussion Top


CD19 is expressed on normal and neoplastic B cells, most plasma cells and follicular dendritic cells. [4] It is however, absent in pro-B cells, which are characterized by CD34 + , CD22 + , TdT + , CD10 , CD19 immunophenotype. [4] PAX-5 is required for the normal expression of CD19 on maturing B cells, which also coincides with Ig gene rearrangements. [5] PAX-5 is located on the short arm of chromosome 9 (9p13). [6] It is expressed from pro-B cell (dim to negative) to mature B cell stage controlling differentiation, function and identity of B cells by repressing 110 genes and activating 170 genes. [7] Blasts in the present case lacked expression of CD19 while expressed TdT, CD10, CD79a and CD22. Hence, they could not be labeled as pro-B cells due to expression of CD10 nor pre-B cell as they lacked CD19. [8] Expression of CD19 is an important prerequisite for B cell lineage assignment. In the absence of CD19, blasts could rarely be assigned to B cell lineage due to expression of CD10, CD79a and CD22; however, caution is warranted due to the relative lack of specificity of CD10 and CD79a. [2]

Abnormalities of the short arm of chromosome 16 including missense mutations of the CD19 gene and deletions or translocations of the chromosome region 9p13 involving PAX-5 gene could be postulated reasons for loss of CD19 in neoplastic B cells. [9] Evaluation of PAX-5 gene status by immunohistochemistry (protein expression) or by FISH (gene study) is recommended, but could not be performed in the present case due to lack of consent from parents of the child for bone marrow procedure at diagnosis.

Cytogenetic analysis of the present case revealed a parent clone with t(3;12)(p21;p12), a random cytogenetic abnormality with no prognostic significance. The neoplastic clone showed further evolution with the emergence of a sub-clone harboring t(9;11)(p21;q23) with involvement of MLL gene. The t(9;11)(p21;q23) is more common in pediatric acute myeloid leukemia (AML) accounting for 9-12% of pediatric AMLs. [10] This translocation leads to the fusion of MLL gene located on chromosome 11q23 with AF9 (MLLT3) gene located on 9p21 and is the most common MLL translocation in AML. [10] It is associated with a very good prognosis in pediatric AMLs. [11] However, it has rarely been described in pediatric B-ALL. [12] The 5-year event-free survival in infants and children aged 1-9 years with t(9;11)(p21;q23) ALL has been reported to be 38% and 50% respectively suggesting a poor prognosis. [12]

MLL gene rearrangements are predominantly associated with a CD10 immunophenotype in ALL. [13] In a study of 184 cases of CD10 B-ALL, Burmeister et al. reported MLL gene rearrangement in 77% of the cases with MLL-AF9 fusion in a single case. Gleissner et al. in their study have reported MLL gene rearrangement in 82% of their CD10 B-ALL cases. [14] Attarbaschi et al. did not find any MLL gene rearrangement in their CD10 + B-ALL cases. [15] In the present case, the leukemic blasts were CD10 + yet showed evidence of MLL gene rearrangement, confirmed by FISH.

To conclude, this case of pediatric CD19, CD10 + B-ALL with t(9;11)(p21;q23) represent a novel case of CD19 negativity in B-ALL with MLL gene rearrangement in CD10 + B cell conferring a very poor prognosis. The exact stage of these blasts in B cell ontogeny remains unexplained and signifies the importance of comprehensive panel of antibody testing by FCM and cytogenetic correlation for correct diagnosis and prognostication of the disease and understanding disease biology.


   Acknowledgment Top


The authors would like to thank Dr. Salil Vaniawala, S.N Gene Lab, Surat for doing cytogenetic and FISH studies for the case.

 
   References Top

1.Zhou LJ, Ord DC, Omori SA, Tedder TF. Structure of the genes encoding the CD19 antigen of human and mouse B lymphocytes. Immunogenetics 1992;35:102-11.  Back to cited text no. 1
    
2.Borowitz MJ, Bene MC, Harris NL, Porwit A, Matutes E. Acute leukemias of ambiguous lineage. In: Swerdlow SH, Campo E, Harris NL, Jaffe ES, Pileri SA, Stein H, et al., editors. WHO Classification of Tumours of Haematopoietic and Lymphoid Tissues. 4 th ed. Geneva: WHO Press; 2008. p. 150-5.  Back to cited text no. 2
    
3.Sultan I, Kraveka JM, Lazarchick J. CD19 negative precursor B acute lymphoblastic leukemia presenting with hypercalcemia. Pediatr Blood Cancer 2004;43:66-9.  Back to cited text no. 3
    
4.Craig FE, Foon KA. Flow cytometric immunophenotyping for hematologic neoplasms. Blood 2008;111:3941-67.  Back to cited text no. 4
    
5.McManus S, Ebert A, Salvagiotto G, Medvedovic J, Sun Q, Tamir I, et al. The transcription factor Pax5 regulates its target genes by recruiting chromatin-modifying proteins in committed B cells. EMBO J 2011;30:2388-404.  Back to cited text no. 5
    
6.Stapleton P, Weith A, Urbánek P, Kozmik Z, Busslinger M. Chromosomal localization of seven PAX genes and cloning of a novel family member, PAX-9. Nat Genet 1993;3:292-8.  Back to cited text no. 6
    
7.Pridans C, Holmes ML, Polli M, Wettenhall JM, Dakic A, Corcoran LM, et al. Identification of Pax5 target genes in early B cell differentiation. J Immunol 2008;180:1719-28.  Back to cited text no. 7
    
8.van Lochem EG, van der Velden VH, Wind HK, te Marvelde JG, Westerdaal NA, van Dongen JJ. Immunophenotypic differentiation patterns of normal hematopoiesis in human bone marrow: Reference patterns for age-related changes and disease-induced shifts. Cytometry B Clin Cytom 2004;60:1-13.  Back to cited text no. 8
    
9.van Zelm MC, Smet J, van der Burg M, Ferster A, Le PQ, Schandené L, et al. Antibody deficiency due to a missense mutation in CD19 demonstrates the importance of the conserved tryptophan 41 in immunoglobulin superfamily domain formation. Hum Mol Genet 2011;20:1854-63.  Back to cited text no. 9
    
10.Byrd JC, Mrózek K, Dodge RK, Carroll AJ, Edwards CG, Arthur DC, et al. Pretreatment cytogenetic abnormalities are predictive of induction success, cumulative incidence of relapse, and overall survival in adult patients with de novo acute myeloid leukemia: Results from Cancer and Leukemia Group B (CALGB 8461). Blood 2002;100:4325-36.  Back to cited text no. 10
    
11.Meshinchi S, Arceci RJ. Prognostic factors and risk-based therapy in pediatric acute myeloid leukemia. Oncologist 2007;12:341-55.  Back to cited text no. 11
    
12.Pui CH, Gaynon PS, Boyett JM, Chessells JM, Baruchel A, Kamps W, et al. Outcome of treatment in childhood acute lymphoblastic leukaemia with rearrangements of the 11q23 chromosomal region. Lancet 2002;359:1909-15.  Back to cited text no. 12
    
13.Burmeister T, Meyer C, Schwartz S, Hofmann J, Molkentin M, Kowarz E, et al. The MLL recombinome of adult CD10-negative B-cell precursor acute lymphoblastic leukemia: Results from the GMALL study group. Blood 2009;113:4011-5.  Back to cited text no. 13
    
14.Gleissner B, Goekbuget N, Rieder H, Arnold R, Schwartz S, Diedrich H, et al. CD10- pre-B acute lymphoblastic leukemia (ALL) is a distinct high-risk subgroup of adult ALL associated with a high frequency of MLL aberrations: Results of the German Multicenter Trials for Adult ALL (GMALL). Blood 2005;106:4054-6.  Back to cited text no. 14
    
15.Attarbaschi A, Mann G, König M, Steiner M, Strehl S, Schreiberhuber A, et al. Mixed lineage leukemia-rearranged childhood pro-B and CD10-negative pre-B acute lymphoblastic leukemia constitute a distinct clinical entity. Clin Cancer Res 2006;12:2988-94.  Back to cited text no. 15
    

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Correspondence Address:
Manu Goyal
Department of Hematopathology, AmPath, American Oncology Institute and Citizens Hospital, Hyderabad, Andhra Pradesh
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0377-4929.130904

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    Abstract
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