Inconclusive flow cytometric surface light chain results; can cytoplasmic light chains, Bcl-2 expression and PCR clonality analysis improve accuracy of cytological diagnoses in B-cell lymphomas?
BACKGROUND
Flow cytometric immunophenotyping (FCI), is widely used in cytology for distinguishing between B-cell lymphoma (BCL) and reactive lymphocytic proliferations (RLP), mainly by identifying monotypic B-cell populations. Since this cannot always be determined by ratios of surface immunoglobulin light chains (sIg LCs) we wanted to assess if cytoplasmic immunoglobulin (cIg) LCs, Bcl-2 and polymerase chain reaction (PCR) based clonality analysis can improve accuracy of cytological diagnoses of BCL.


METHODS
Our study included 98 fine needle aspiration biopsies from lymph nodes suspicious for BCL with inconclusive sIg LCs. In all cases PCR clonality analysis was performed in order to determine immunoglobulin heavy chain (IGH) gene and T-cell receptor (TRC) gene rearrangement. In selected cases expression of Bcl-2 and cIg LC were determined by FC.


RESULTS
Thirty patients had lymphoma and 68 had reactive lymphocytic proliferations. Three patterns of sIg LCs staining were found: negative, dual positive and difficult to interpret. Percentage of lymphomas was highest in the dual positive group (75 %). Morphology coupled with cIg LCs determination and/or Bcl-2 expression was able to give a correct diagnosis in 83 % of cases. Molecular tests would have been misleading in 15 % of cases because 7/30 BCL were polyclonal and 8/68 RLP were monoclonal.


CONCLUSIONS
Determination of cIg LCs, Bcl-2 expression and PCR clonality analysis of B cells improved accuracy of cytological diagnoses in BCL with inconclusive sIg LC. However, clonality determined by PCR was misleading in some cases.
Department of Experimental Oncology, Institute of Oncology, Ljubljana, Slovenia. abrozic@onko-i.si.
Andreja
A
Brozic
Department of Cytopathology, Institute of Oncology, Ljubljana, Slovenia. zpohar@onko-i.si.
Ziva
Z
Pohar Marinsek
Department of Molecular Diagnostic, Institute of Oncology, Ljubljana, Slovenia. snovakovic@onko-i.si.
Srdjan
S
Novakovic
Department of Cytopathology, Institute of Oncology, Ljubljana, Slovenia. vkloboves@onko-i.si.
Veronika
V
Kloboves Prevodnik
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D014408:Biomarkers, Tumor / Q000032:analysis / Q000235:genetics; D044963:Biopsy, Fine-Needle; D049109:Cell Proliferation; D002648:Child; D002675:Child, Preschool; D003593:Cytoplasm / Q000276:immunology*; D005260:Female; D005434:Flow Cytometry; D015322:Gene Rearrangement, B-Lymphocyte; D050438:Genes, Immunoglobulin Heavy Chain; D019672:Genes, T-Cell Receptor; D006801:Humans; D007147:Immunoglobulin Light Chains / Q000032:analysis*; D016130:Immunophenotyping / Q000379:methods*; D008198:Lymph Nodes / Q000737:chemistry / Q000276:immunology / Q000473:pathology; D016393:Lymphoma, B-Cell / Q000737:chemistry / Q000175:diagnosis* / Q000235:genetics / Q000276:immunology; D008297:Male; D008875:Middle Aged; D016133:Polymerase Chain Reaction; D011237:Predictive Value of Tests; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000032:analysis*; D015203:Reproducibility of Results; D055815:Young Adult
C000595707:BCL2 protein, human; D014408:Biomarkers, Tumor; D007147:Immunoglobulin Light Chains; D019253:Proto-Oncogene Proteins c-bcl-2