Flow Cytometric Detection of CD79a Expression in T-Cell Acute Lymphoblastic Leukemias

Abstract

We evaluated the lineage specificity of CD79a in acute leukemias using 3-color flow cytometry in 58 consecutive cases. A panel of cell-surface antigens, including myeloid-associated markers, B-cell-associated markers, and T-cell-associated markers, was used. All cases of acute myeloid leukemia were CD79a-, whereas all cases of B-lineage acute lymphoblastic leukemia (ALL) were CD79a+. Three of 8 cases of T-cell ALL showed variable CD79a expression, indicating the presence of a blast subset expressing a relatively high level of CD79a. We investigated the clinical and pathologic characteristics of these 3 cases. All 3 cases had L1 or L2 morphology and expressed surface CD3. None of the other B-cell-associated markers were positive, although 1 case expressed CD13 and CD33. Uncommon random karyotypic abnormalities were identified in all 3 cases. Molecular studies demonstrated monoclonal gene rearrangement of T-cell receptor gamma in 2 of 3 cases. All 3 patients were 18 years old or younger; 1 patient did not enter remission, and 1 had disease relapse in 8 months. Our findings provide further support for the existence of a subset of T-cell ALL coexpressing CD3 and CD79a. Further study of the clinical and biologic significance of this subset may be warranted.

IgH DJ rearrangements within T-ALL correlate with cCD79a expression, an immature/TCRγδ phenotype and absence of IL7Rα/CD127 expression

“…4,5 It is considered to represent a B lineage restricted marker, 6 although weak cCD79a expression has been detected by immunohistochemistry or flow cytometry in 10-40% of a limited number of T-ALLs. [7][8][9][10] Incomplete immunoglobulin (Ig) DJ rearrangements first occur in CD34 þ , CD19À, CD10 þ , cCD79a þ early B cells, whereas VDJ rearrangements commence in CD19 þ , pro-B cells, just prior to appearance of cytoplasmic Igm and pre-BCR expression. [11][12][13] Whether the earliest IgH DJ rearranged, CD79a þ precursors are B lymphoid restricted is not clear.…”

Revised guideline on immunophenotyping in acute leukaemias and chronic lymphoproliferative disorders

“…The majority of B-lineage acute lymphoblastic leukaemias (ALL) are CD79a-positive while reactions are usually negative in acute myeloid leukaemias (AML) (Buccheri et al, 1993). Although there have been two reports describing CD79a expression in T lineage ALL (Pilozzi et al, 1998;Lai et al, 2000), the signi®cance of these ®ndings is still uncertain. One of the two studies (Lai et al, 2000) documented three T-ALL cases whose cells expressed CD79a weakly.…”

“…Although there have been two reports describing CD79a expression in T lineage ALL (Pilozzi et al, 1998;Lai et al, 2000), the signi®cance of these ®ndings is still uncertain. One of the two studies (Lai et al, 2000) documented three T-ALL cases whose cells expressed CD79a weakly. However, two of these cases were also CD10-positive qualifying as biphenotypic acute leukaemia (B plus T lymphoid) (Matutes et al, 1997;Bene et al, 1998b;Brunning et al, 2001).…”

Immunophenotypic Profile in Adult Patients with Acute Leukemia Association with Clinical Feature: Fluorescence Cytometry Quantitative Analysis

“…CD79a is a highly lineage-specific marker of B lymphoid cells and plays an important role in the diagnosis of acute leukemia [42]. In this study 33% of B-ALL cases express CD79a.…”