The "CD43 only" phenotype. An aberrant, nonspecific immunophenotype requiring comprehensive analysis for lineage
G H Segal1, M H Stoler, R R Tubbs
1Department of Pathology, Cleveland Clinic Foundation, Ohio 44195.
Insights
The CD43 marker alone is not specific for T-cell lineage in leukocytic proliferations. This immunophenotyping finding can misidentify various B-cell and myeloid malignancies as T-cell lymphomas.
Area of Science:
- Hematopathology
- Immunohistochemistry
- Flow Cytometry
Background:
- Paraffin section immunohistology is standard for immunophenotyping leukocytic proliferations.
- A common antibody panel includes CD20, CD43, and CD45RO.
- While reliable for B-cell lineage, T-cell characterization is less definitive due to reagent specificity issues.
Purpose of the Study:
- To evaluate the diagnostic utility and specificity of the CD43 marker in paraffin section immunohistochemistry.
- To highlight the limitations of a "CD43 only" phenotype in diagnosing T-cell lineage.
Main Methods:
- Retrospective analysis of 17 cases with a "CD43 only" phenotype using a standard antibody screening panel.
- Comparison of immunophenotypic findings with clinical, morphologic, and genotypic data.
Main Results:
- Cases with a "CD43 only" phenotype were heterogeneous, including myeloid leukemias, T-cell lymphomas, B-cell lymphomas, and plasmacytomas.
- The "CD43 only" phenotype was not specific for T-cell proliferations, with most cases being myeloid or B-cell in origin.
Conclusions:
- The CD43 marker, while useful, exhibits aberrant reactivity and lacks specificity.
- Caution is advised when assigning lineage based solely on a "CD43 only" phenotype.
- Additional immunologic or genotypic analysis is recommended for accurate diagnosis of leukocytic proliferations.
Abstract:
Paraffin section immunohistology of leukocytic proliferations is a routine method of immunophenotyping in many clinical laboratories. Furthermore, a relatively standard antibody screening panel that includes L26 (CD20), Leu22 (CD43), and UCHL1 (CD45RO) appears to be widely used. Although paraffin section immunophenotyping in general, and this panel in particular, have been shown to be very reliable in defining B-cell lineage, characterization of T-cell lineage is less definitive. This is related primarily to the relatively poor specificity of the commercially available T-cell-associated reagents. CD43 (Leu22) in particular has a broad immunoreactivity profile that has not been stressed adequately in some reports. Seventeen cases with a "CD43 only" phenotype were identified during the last several years while using the relatively standard screening panel mentioned above. These cases were quite heterogeneous with respect to cellular differentiation and most were not T-cell proliferations. Specifically, eight cases were extramedullary leukemic infiltrates (five myeloid, two monocytic, one mixed lineage), four cases were T-cell lymphomas, three cases were B-cell lymphomas and two cases were plasmacytomas. Although CD43 has demonstrable utility in a leukocyte screening panel, this report stresses the aberrancy and lack of specificity of the "CD43 only" phenotype. Caution is recommended in assigning a specific lineage to such cellular proliferations without additional immunologic or genotypic analysis. Recommendations for comprehensive diagnostic evaluation of these proliferations are provided.
