| Abstract|| |
B-lineage acute lymphoblastic leukemia (B-ALL) is an aggressive neoplasm of B-lymphocyte precursors that express the pan B-cell marker CD19 in all the cases. Rarely, a case may be assigned as B-lineage even if CD19 is negative.
Here, a 16-year-old male presented with complaints of pain abdomen, on and off fever, joint pain, and hepatosplenomegaly for 2 months. Bone marrow examination was suggestive of acute leukemia with numerous leukoblasts on aspiration. On flow cytometry, gated blast population was negative for CD19, cytoCD3, and myeloperoxidase MPO and positive for CD34, TdT, HLA-DR, CD22, CD79a, and CD10. Immunohistochemistry study showed positivity for TdT, CD34, CD10 (focal), and PAX 5 and negativity for CD20, CD3, MPO, CD117, and CD68. Lack of awareness of negative CD19 expression in B-ALL can lead to incorrect immunophenotypic diagnosis, treatment, and monitoring of B-ALL. Proper diagnosis should be based on clinical features, immunophenotypic profiles, immunohistochemistry findings, and molecular analysis.
Keywords: B-lineage acute lymphoblastic leukemia, CD19 negative, flow cytometric immunophenotyping
|How to cite this article:|
Bansal S, Sharma U, Jain A, Sharma R, Yagnik B. CD19-negative B-lineage acute lymphoblastic leukemia: A diagnostic and therapeutic challenge. Indian J Pathol Microbiol 2017;60:596-8
|How to cite this URL:|
Bansal S, Sharma U, Jain A, Sharma R, Yagnik B. CD19-negative B-lineage acute lymphoblastic leukemia: A diagnostic and therapeutic challenge. Indian J Pathol Microbiol [serial online] 2017 [cited 2019 Jun 20];60:596-8. Available from: http://www.ijpmonline.org/text.asp?2017/60/4/596/222976
| Introduction|| |
Acute lymphoblastic leukemia of B-lineage (B-ALL) is an aggressive neoplasm of B-lymphocyte precursors that express the pan B-cell marker CD19 in all the cases. CD19 plays a pivotal role as a “gating” antigen in the analysis of leukemic cells by flow cytometric immunophenotyping (FCI). CD19 gene is located on the short arm of chromosome 16, 16p11.2. Expression of CD19 on blasts is considered as the most reliable marker for assigning them to the B-lineage. Rarely, a case may be assigned as B-lineage even if CD19 is negative. Hence, it would be challenging to diagnose and treat B-ALL without CD19 expression.
| Case Report|| |
A 16-year-old male patient presented with complaints of pain abdomen, on and off high-grade fever, and joint pain for 2 months. Ultrasonography revealed hepatosplenomegaly. Complete blood count analysis showed hemoglobin (Hb) 6.7 g/dl, total leukocyte count (TLC) 2430/μl, and platelet count 37,000/μl, and in peripheral blood film examination 15% blast population was observed. Liver function tests, renal function tests, and uric acid were within normal limits.
Bone marrow aspirate revealed hypercellular marrow with numerous leukoblasts. Biopsy showed hypercellular marrow with markedly suppressed normal hematopoietic tissue, and marrow spaces were massively infiltrated by leukoblasts, suggestive of acute leukemia. Cytochemistry was not informative.
FCI was done on bone marrow sample. Specimen was acquired using BD FACS CANTO II instrument and analyzed with DIVA software (Becton Dickinson, US). A blank tube was run and acquired before acquisition of blood specimen to avoid carryover. A maximum of 30,000 events were acquired per tube, where 36% of gated population in blast window expressed only few B-lymphoblast markers CD10 (heterogenous), cytoCD22 (dim), and CD79a (homogenous) with CD34, TdT, and HLA-DR. Rest of the T-cell markers (CD1a, CD2, CD3, CD4, CD5, CD7, CD8, CD16, CD56, and cytoCD3), B-cell markers (CD19, CD20), and myeloid/monocytoid markers (CD13, CD33, MPO, CD117, CD11c, CD14, CD36, CD41, and CD235a) were negative [Figure 1]. In the absence of other lineage-specific markers (Cyto CD3 and MPO) but presence of three B-lineage-associated markers, diagnosis of CD19-negative precursor B-ALL was suggested.
|Figure 1: Flow cytometric immunophenotyping graphs. Blasts are shown in red, lymphocyte in green, and maturing myeloid cells in blue. (a) 36% blasts, (b) TdT positivity, (c) statistics, (d and e) CD19 negativity, (f) CD34-positive leukoblasts with dim CD22 positivity, (g and h) CD79a positivity with MPO and CD5 negativity, and (i) heterogenous CD10 positivity|
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Immunohistochemistry study of bone marrow biopsy showed TdT, CD34, CD10 (focal), and PAX5 positivity and CD20, CD3, CD117, MPO, and CD68 negativity, which further supported B-immunophenotype. Cytogenetic study showed two kinds of metaphases: 20% were hyperdiploid and the remaining 80% did not show any structural or numerical abnormality. Qualitative translocation panel studied by multiplex reverse-transcriptase polymerase chain reaction and gel electrophoresis did not reveal any of following chromosomal anomalies: t(9;22)(q34;q11), t(12;21)(p13;q22), t(1;19)(q23;p13), and t(4;11)(q21;q23). The hybrid transcripts for BCR/ABL1, ETV6/RUNX1, E2A/PBX1, and MLL/AF4 were also not detected in the leukocytes of the specimen.
Following thorough investigation, the patient received standard chemotherapy for ALL. One month after induction therapy, bone marrow revealed 90% cellularity with erythroid prominence and normal myeloid and megakaryocytic series. Overall marrow of the patient was in morphological remission. Now, the patient is in consolidation phase with Hb 11.5 g/dl, TLC 8900/μl, platelets 270,000/μl, with no blast in peripheral blood film.
| Discussion|| |
CD19 is a B-cell-specific marker, expressed on all stages of B-lymphocytes including plasma cells. It is widely used in the FCI of B-cell and plasma cell malignancies. B-ALL is characterized by CD19 expression, which is one of the most important prerequisites, along with expression of CD10, CD22, and/or CD79a. Blasts in the present case show negativity for CD19, while expressed TdT, CD34, CD10, CD79a, and CD22. Negativity for CD19 in cases of B-ALL is quite unusual; however, very few cases have been reported in the literature.
Ghodke et al. studied three cases of rare CD19-negative B-ALL which were diagnosed as B-ALL based on the expression of CD10, CD20, CD22, CD34, and CD79a. CD19 was severely downregulated in all the three cases. Cytogenetic studies were negative for recurrent translocations. Moon et al. reported a case of a 6-year-old girl with CD45-negative and CD19-negative precursor B-ALL presenting with an atypical morphology. Sultan et al. reported a case report of a 9-month-old infant with CD19-negative B-ALL presenting with hypercalcemia. On FCI, the cells were dim CD45, HLA-DR, and CD10 positive, but CD19, CD20, CD79a, and CD34 negative. Weiland et al. in his letter to the editor concluded that B cell precursor ALL cell lines and blasts are not dependent on CD19 expression for survival and propagation.
Reports of CD19-negative B-ALL are rare. However, lack of awareness of negative CD19 expression in B-ALL can lead to incorrect immunophenotypic diagnosis, treatment, and monitoring of B-ALL. Proper diagnosis should be based on clinical features, immunophenotype profiles, immunohistochemistry findings, and molecular analysis.
It is essential to diagnose very rare occurrences of CD19-negative B-ALL, which should not be mistaken for acute leukemia of undifferentiated origin which has a poor prognosis and different treatment strategy.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
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Conflicts of interest
There are no conflicts of interest.
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Department of Pathology, Bhagwan Mahaveer Cancer Hospital and Research Centre, JLN Marg., Jaipur - 302 017, Rajasthan
Source of Support: None, Conflict of Interest: None