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Multiplexed Fluorescent Immunohistochemical Staining, Imaging, and Analysis in Histological Samples of Lymphoma
Published on: January 9, 2019
Genotypic analysis of diffuse, mixed cell lymphomas. Comparison with morphologic and immunophenotypic findings
L J Medeiros1, P Lardelli, M Stetler-Stevenson
1Hematopathology Section, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892.
Insights
Gene rearrangement analysis aids in diagnosing diffuse mixed cell lymphomas when immunophenotyping is unclear. This molecular technique, alongside Southern blot analysis, confirms clonality and identifies specific genetic translocations, expanding the understanding of lymphoma subtypes.
Area of Science:
- Hematology
- Molecular Pathology
- Oncology
Background:
- Malignant lymphoma, diffuse, mixed small and large cell type, presents diagnostic challenges due to morphological and immunophenotypic heterogeneity.
- Determining clonality is crucial for accurate diagnosis, but can be difficult with conventional methods.
Purpose of the Study:
- To evaluate the utility of gene rearrangement analysis in diagnosing diffuse mixed cell lymphomas.
- To compare genotypic findings with immunophenotypic and histologic data.
- To investigate the presence of the t(14;18) translocation in B-cell lymphomas.
Main Methods:
- Genotyping 20 cases of diffuse mixed cell lymphoma using gene rearrangement analysis.
- Performing immunophenotypic studies to assess cell populations.
- Utilizing Southern blot analysis and/or polymerase chain reaction to detect the t(14;18) translocation.
Main Results:
- Gene rearrangement analysis confirmed clonality in cases where immunophenotyping was uncertain or showed aberrant phenotypes.
- The t(14;18) translocation was identified in seven B-cell lymphomas, including five not morphologically classified as follicular center cell type.
- Immunophenotypic studies revealed predominantly T-cell populations, with some cases showing monoclonal B-cell populations or aberrant phenotypes.
Conclusions:
- Gene rearrangement analysis is a valuable adjunct to immunophenotypic studies for diagnosing diffuse mixed cell lymphomas.
- The findings suggest a broader histologic spectrum for follicular center cell lymphomas than previously recognized.
- Molecular techniques enhance the diagnostic accuracy and classification of lymphoma subtypes.
Abstract:
Malignant lymphoma, diffuse, mixed small and large cell type, as defined in the Working Formulation, is heterogeneous both morphologically and immunophenotypically and, in some cases, clonality may be difficult to determine. Because gene rearrangement analysis has been shown to be a sensitive method for determining clonality, the authors genotyped 20 cases and compared the results with histologic and immunophenotypic findings. Immunophenotypic studies demonstrated that all lesions were composed predominantly of T cells. In addition, in eight cases either a monoclonal B-cell population (five lesions) or an aberrant immunophenotype (two T, one B) was detected, supporting a malignant diagnosis. In seven of these eight lymphomas, genotypic analysis confirmed the presence of a population of clonal cells. One case with an abnormal T-cell phenotype was germline. In 12 cases the immunophenotypic results were uncertain (i.e., no clonal population or abnormal immunophenotype was identified). Genotypic analysis provided evidence of clonality in eight. In four cases with uncertain immunophenotypic results, a clonal population also could not be identified with the use of Southern blot analysis. Thus, the authors conclude that gene rearrangement analysis is a valuable tool in the study of diffuse mixed cell lymphomas and is complementary to immunophenotypic studies. In addition, the authors analyzed the major breakpoint region of the bcl-2 protooncogene on chromosome 18, either by Southern blot analysis and/or with the polymerase chain reaction. The authors identified the t(14;18)(q32;q21) translocation in seven B-cell lymphomas, five of which were not considered to be of follicular center cell type on the basis of morphologic findings. These results suggest that the histologic spectrum of follicular center cell lymphomas is greater than is appreciated in the literature.
