title: CD19 negative precursor B acute lymphoblastic leukemia (B-ALL)-Immunophenotypic challenges in diagnosis and monitoring: A study of three cases.
abstract: CD19 is a B-cell specific marker, expressed on all stages of B-lymphocytes including plasma cells. It is widely used in the flow cytometric immunophenotyping (FCI) of B-cell and plasma cell malignancies. The analysis approach of FCI for the diagnosis and monitoring of B-cell acute lymphoblastic leukemia (B-ALL) is totally based on the CD19-based primary gating strategy and it would be challenging to study B-ALL without CD19 expression. Since CD19 negative B-ALL are extremely rare, we report three cases of B-ALL with negative expression of CD19 and discussed its implication in the diagnosis, residual disease monitoring and future targeted therapy.
  
  
  
  Peripheral blood (PB) and bone marrow (BM) samples from three cases suspicious of acute leukemia were studied for morphology, cytochemistry, immunophenotyping and cytogenetics. FCI was performed using a comprehensive six to eight-color multiparametric assay. The cytogenetic studies for standard recurrent genetic translocations were performed by FISH & Karyotyping.
  
  
  
  The three cases studied were diagnosed as B-ALL based on the expression of CD10, CD20, CD22, CD34, and CD79a by leukemic blasts. CD19 was studied using two different clones (i.e. J3-119 & HIB-19) and found to be severely down regulated in all three cases. There were no significant differentiating features in morphology. Cytogenetic studies were negative for recurrent translocations.
  
  
  
  We report three cases of extremely rare CD19 negative B-ALL. Lack of awareness of negative CD19 expression in B-ALL can leads to incorrect immunophenotypic diagnosis and monitoring of B-ALL, especially in laboratories using limited markers. © 2016 International Clinical Cytometry Society.
authors.affiliation: Hematopathology Laboratory, Department of Pathology, Tata Memorial Centre, Mumbai, India.
authors.forename: Kiran
authors.initials: K
authors.lastname: Ghodke
authors.affiliation: Hematopathology Laboratory, Department of Pathology, Tata Memorial Centre, Mumbai, India.
authors.forename: Asma
authors.initials: A
authors.lastname: Bibi
authors.affiliation: Hematopathology Laboratory, Department of Pathology, Tata Memorial Centre, Mumbai, India.
authors.forename: Nikhil
authors.initials: N
authors.lastname: Rabade
authors.affiliation: Hematopathology Laboratory, Department of Pathology, Tata Memorial Centre, Mumbai, India.
authors.forename: Nikhil
authors.initials: N
authors.lastname: Patkar
authors.affiliation: Hematopathology Laboratory, Department of Pathology, Tata Memorial Centre, Mumbai, India.
authors.forename: P G
authors.initials: PG
authors.lastname: Subramanian
authors.affiliation: Department of Cancer Cytogenetics, Tata Memorial Centre, Mumbai, India.
authors.forename: Pratibha Aamre
authors.initials: PA
authors.lastname: Kadam
authors.affiliation: Hematopathology Laboratory, Department of Pathology, Tata Memorial Centre, Mumbai, India.
authors.forename: Y
authors.initials: Y
authors.lastname: Badrinath
authors.affiliation: Hematopathology Laboratory, Department of Pathology, Tata Memorial Centre, Mumbai, India.
authors.forename: Sitaram
authors.initials: S
authors.lastname: Ghogale
authors.affiliation: Hematopathology Laboratory, Department of Pathology, Tata Memorial Centre, Mumbai, India.
authors.forename: Sumeet
authors.initials: S
authors.lastname: Gujral
authors.affiliation: Hematopathology Laboratory, Department of Pathology, Tata Memorial Centre, Mumbai, India.
authors.forename: Prashant
authors.initials: P
authors.lastname: Tembhare
mesh_terms: D000328:Adult; D000906:Antibodies / Q000737:chemistry; D015703:Antigens, CD / Q000235:genetics / Q000276:immunology; D018941:Antigens, CD19 / Q000235:genetics* / Q000276:immunology; D001402:B-Lymphocytes / Q000276:immunology / Q000473:pathology*; D001854:Bone Marrow Cells / Q000276:immunology / Q000473:pathology*; D002648:Child; D002675:Child, Preschool; D015536:Down-Regulation; D005260:Female; D005434:Flow Cytometry; D015870:Gene Expression; D006801:Humans; D016130:Immunophenotyping / Q000379:methods*; D007621:Karyotyping; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000175:diagnosis* / Q000235:genetics / Q000276:immunology / Q000473:pathology
chemical_list: D000906:Antibodies; D015703:Antigens, CD; D018941:Antigens, CD19; C000604811:CD19 molecule, human
keywords: B-cell acute lymphoblastic leukemia; CD19; Flow cytometric immunophenotyping (FCI)