Flow Cytometric Immunophenotyping
Flow Cytometric Immunophenotyping
We studied the flow cytometric immunophenotyping (FCI) and genotypic data of 11 specimens from 10 transplant recipients and categorized them based on a scheme for posttransplant lymphoproliferative disorders (PTLDs). Specimens had been analyzed by polymerase chain reaction and/or Southern blot for T-cell and B-cell (immunoglobulin heavy chain and light chain genes) gene rearrangements (BGR).
The categories for PTLDs were as follows: 1, 1; 2, 6; and 3, 4. The plasmacytic and polymorphic B-cell hyperplasias (PBCHs) revealed no monoclonal/aberrant cells by FCI or genotypic studies (GS). Three of 4 polymorphic B-cell lymphomas (PBCLs) revealed monoclonal or aberrant (no surface light chain) B cells by FCI; 1 of 3 revealed a BGR. However, the 1 case with no monoclonal/aberrant B cells by FCI revealed a BGR. Both immunoblastic lymphomas revealed monoclonal or aberrant B cells by FCI; 1 revealed a BGR. Both multiple myelomas revealed monoclonal plasma cells by FCI; 1 revealed a BGR. In the 4 PTLDs with monoclonal/aberrant B cells by FCI and no clonality detected by GS, the GS were performed on fresh and paraffin-embedded tissue samples.
FCI of the plasmacytic and PBCHs supported no clonal process by GS. FCI defined a clonal process in 2 PBCLs, 1 immunoblastic lymphoma, and 1 multiple myeloma that were negative by GS. However, 1 PBCL that was polyclonal by FCI was monoclonal by GS. Thus, FCI is useful for identifying a clonal process in PTLDs with negative results by GS; FCI and GS should be performed routinely in PTLDs to detect a clonal process.
Posttransplant lymphoproliferative disorders (PTLDs) represent a morphologic, immunophenotypic, and genotypic spectrum of disease. The spectrum ranges from polymorphic, polyclonal proliferations with many features of a florid viral infection at one end to monomorphic, monoclonal proliferations, usually of the B-cell type, at the other end.
Authors' attempts to categorize PTLDs have been based on a variety of criteria, including morphologic features and analysis of clonality (predominantly by genotypic techniques). In 1981, Frizzera et al described 2 major distinctive types of PTLD in renal transplant recipients: polymorphic diffuse B-cell hyperplasia (lacking necrosis and "atypical immunoblasts") and polymorphic diffuse B-cell lymphoma. In 1988, Nalesnik et al described the pathology of PTLDs occurring in the setting of cyclosporine-prednisone immunosuppression. Based on morphologic features, they divided PTLDs into 3 categories: (1) polymorphic (necrosis is most pronounced with atypical immunoblasts most frequently seen), (2) monomorphic (resembles Burkitt or centroblastic lymphoma; indistinguishable from non-Hodgkin lymphoma), and (3) minimal polymorphism (predominance of plasmacytoid lymphocytes and plasma cells).
More recently, in 1995, Knowles et al proposed dividing PTLDs into 3 distinct categories based on a combination of morphologic and genotypic studies. These categories are as follows:
In this diagnostic scheme, determination of clonality is thus important in PTLDs to categorize the process and to manage the treatment of the patient. As mentioned, analysis of clonality has been determined predominantly by genotypic techniques.
Analysis of clonality in PTLDs by immunophenotyping has primarily consisted of immunohistochemical studies that have usually yielded indeterminate results. Determination of clonality by flow cytometric immunophenotyping (FCI) in excised biopsy specimens of PTLD has been described by Kowal-Vern et al. However, a complete immunophenotypic profile by FCI was performed in only 1 case; only 4 cases underwent FCI analysis of B-cell markers (CD19 and CD20).
Thus, the purposes of the present study were to describe the morphologic, immunohistochemical, and FCI findings based on a comprehensive analysis of FCI markers in PTLDs and systematically compare the results with those of genotypic studies.
We studied the flow cytometric immunophenotyping (FCI) and genotypic data of 11 specimens from 10 transplant recipients and categorized them based on a scheme for posttransplant lymphoproliferative disorders (PTLDs). Specimens had been analyzed by polymerase chain reaction and/or Southern blot for T-cell and B-cell (immunoglobulin heavy chain and light chain genes) gene rearrangements (BGR).
The categories for PTLDs were as follows: 1, 1; 2, 6; and 3, 4. The plasmacytic and polymorphic B-cell hyperplasias (PBCHs) revealed no monoclonal/aberrant cells by FCI or genotypic studies (GS). Three of 4 polymorphic B-cell lymphomas (PBCLs) revealed monoclonal or aberrant (no surface light chain) B cells by FCI; 1 of 3 revealed a BGR. However, the 1 case with no monoclonal/aberrant B cells by FCI revealed a BGR. Both immunoblastic lymphomas revealed monoclonal or aberrant B cells by FCI; 1 revealed a BGR. Both multiple myelomas revealed monoclonal plasma cells by FCI; 1 revealed a BGR. In the 4 PTLDs with monoclonal/aberrant B cells by FCI and no clonality detected by GS, the GS were performed on fresh and paraffin-embedded tissue samples.
FCI of the plasmacytic and PBCHs supported no clonal process by GS. FCI defined a clonal process in 2 PBCLs, 1 immunoblastic lymphoma, and 1 multiple myeloma that were negative by GS. However, 1 PBCL that was polyclonal by FCI was monoclonal by GS. Thus, FCI is useful for identifying a clonal process in PTLDs with negative results by GS; FCI and GS should be performed routinely in PTLDs to detect a clonal process.
Posttransplant lymphoproliferative disorders (PTLDs) represent a morphologic, immunophenotypic, and genotypic spectrum of disease. The spectrum ranges from polymorphic, polyclonal proliferations with many features of a florid viral infection at one end to monomorphic, monoclonal proliferations, usually of the B-cell type, at the other end.
Authors' attempts to categorize PTLDs have been based on a variety of criteria, including morphologic features and analysis of clonality (predominantly by genotypic techniques). In 1981, Frizzera et al described 2 major distinctive types of PTLD in renal transplant recipients: polymorphic diffuse B-cell hyperplasia (lacking necrosis and "atypical immunoblasts") and polymorphic diffuse B-cell lymphoma. In 1988, Nalesnik et al described the pathology of PTLDs occurring in the setting of cyclosporine-prednisone immunosuppression. Based on morphologic features, they divided PTLDs into 3 categories: (1) polymorphic (necrosis is most pronounced with atypical immunoblasts most frequently seen), (2) monomorphic (resembles Burkitt or centroblastic lymphoma; indistinguishable from non-Hodgkin lymphoma), and (3) minimal polymorphism (predominance of plasmacytoid lymphocytes and plasma cells).
More recently, in 1995, Knowles et al proposed dividing PTLDs into 3 distinct categories based on a combination of morphologic and genotypic studies. These categories are as follows:
Plasmacytic hyperplasia characteristically involves the oropharynx or nodal sites, is nearly always polyclonal, usually contains multiple Epstein-Barr virus (EBV) infection events, and lacks oncogene and tumor suppressor gene alterations.
Polymorphic B-cell hyperplasia and polymorphic B-cell lymphoma (PBCL) may arise nodally or extranodally, are nearly always monoclonal, usually contain a single form of EBV, and lack oncogene and tumor suppressor gene alterations.
Immunoblastic lymphoma and multiple myeloma represent widely disseminated disease of monoclonal origin containing a single form of EBV and alterations of 1 or more oncogene or tumor suppressor genes (ie, N-ras, p53, c-myc).
In this diagnostic scheme, determination of clonality is thus important in PTLDs to categorize the process and to manage the treatment of the patient. As mentioned, analysis of clonality has been determined predominantly by genotypic techniques.
Analysis of clonality in PTLDs by immunophenotyping has primarily consisted of immunohistochemical studies that have usually yielded indeterminate results. Determination of clonality by flow cytometric immunophenotyping (FCI) in excised biopsy specimens of PTLD has been described by Kowal-Vern et al. However, a complete immunophenotypic profile by FCI was performed in only 1 case; only 4 cases underwent FCI analysis of B-cell markers (CD19 and CD20).
Thus, the purposes of the present study were to describe the morphologic, immunohistochemical, and FCI findings based on a comprehensive analysis of FCI markers in PTLDs and systematically compare the results with those of genotypic studies.
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