The genomic landscape of mantle cell lymphoma is related to the epigenetically determined chromatin state of normal B cells.

In this study, we define the genetic landscape of mantle cell lymphoma (MCL) through exome sequencing of 56 cases of MCL. We identified recurrent mutations in ATM, CCND1, MLL2, and TP53. We further identified a number of novel genes recurrently mutated in patients with MCL including RB1, WHSC1, POT1, and SMARCA4. We noted that MCLs have a distinct mutational profile compared with lymphomas from other B-cell stages. The ENCODE project has defined the chromatin structure of many cell types. However, a similar characterization of primary human mature B cells has been lacking. We defined, for the first time, the chromatin structure of primary human naïve, germinal center, and memory B cells through chromatin immunoprecipitation and sequencing for H3K4me1, H3K4me3, H3Ac, H3K36me3, H3K27me3, and PolII. We found that somatic mutations that occur more frequently in either MCLs or Burkitt lymphomas were associated with open chromatin in their respective B cells of origin, naïve B cells, and germinal center B cells. Our work thus elucidates the landscape of gene-coding mutations in MCL and the critical interplay between epigenetic alterations associated with B-cell differentiation and the acquisition of somatic mutations in cancer.

Genetic heterogeneity of diffuse large B-cell lymphoma.

Diffuse large B-cell lymphoma (DLBCL) is the most common form of lymphoma in adults. The disease exhibits a striking heterogeneity in gene expression profiles and clinical outcomes, but its genetic causes remain to be fully defined. Through whole genome and exome sequencing, we characterized the genetic diversity of DLBCL. In all, we sequenced 73 DLBCL primary tumors (34 with matched normal DNA). Separately, we sequenced the exomes of 21 DLBCL cell lines. We identified 322 DLBCL cancer genes that were recurrently mutated in primary DLBCLs. We identified recurrent mutations implicating a number of known and not previously identified genes and pathways in DLBCL including those related to chromatin modification (ARID1A and MEF2B), NF-κB (CARD11 and TNFAIP3), PI3 kinase (PIK3CD, PIK3R1, and MTOR), B-cell lineage (IRF8, POU2F2, and GNA13), and WNT signaling (WIF1). We also experimentally validated a mutation in PIK3CD, a gene not previously implicated in lymphomas. The patterns of mutation demonstrated a classic long tail distribution with substantial variation of mutated genes from patient to patient and also between published studies. Thus, our study reveals the tremendous genetic heterogeneity that underlies lymphomas and highlights the need for personalized medicine approaches to treating these patients.

miRNA expression in diffuse large B-cell lymphoma treated with chemoimmunotherapy.

Diffuse large B-cell lymphoma (DLBCL) prognostication requires additional biologic markers. miRNAs may constitute markers for cancer diagnosis, outcome, or therapy response. In the present study, we analyzed the miRNA expression profile in a retrospective multicenter series of 258 DLBCL patients uniformly treated with chemoimmunotherapy. Findings were correlated with overall survival (OS) and progression-free survival (PFS). miRNA and gene-expression profiles were studied using microarrays in an initial set of 36 cases. A selection of miRNAs associated with either DLBCL molecular subtypes (GCB/ABC) or clinical outcome were studied by multiplex RT-PCR in a test group of 240 cases with available formalin-fixed, paraffin-embedded (FFPE) diagnostic samples. The samples were divided into a training set (123 patients) and used to derive miRNA-based and combined (with IPI score) Cox regression models in an independent validation series (117 patients). Our model based on miRNA expression predicts OS and PFS and improves upon the predictions based on clinical variables. Combined models with IPI score identified a high-risk group of patients with a 2-year OS and a PFS probability of < 50%. In summary, a precise miRNA signature is associated with poor clinical outcome in chemoimmunotherapy-treated DLBCL patients. This information improves upon IPI-based predictions and identifies a subgroup of candidate patients for alternative therapeutic regimens.

Patients with diffuse large B-cell lymphoma of germinal center origin with BCL2 translocations have poor outcome, irrespective of MYC status: a report from an International DLBCL rituximab-CHOP Consortium Program Study.

Diffuse large B-cell lymphoma can be classified by gene expression profiling into germinal center and activated B-cell subtypes with different prognoses after rituximab-CHOP. The importance of previously recognized prognostic markers, such as Bcl-2 protein expression and BCL2 gene abnormalities, has been questioned in the new therapeutic era. We analyzed Bcl-2 protein expression, and BCL2 and MYC gene abnormalities by interphase fluorescence in situ hybridization in 327 patients with de novo disease treated with rituximab-CHOP. Isolated BCL2 and MYC rearrangements were not predictive of outcome in our patients as a whole, but only in those with the germinal center subtype of lymphoma. The prognostic relevance of isolated MYC rearrangements was weaker than that of BCL2 isolated translocations, but was probably limited by the rarity of the rearrangements. Seven of eight patients with double hit lymphoma had the germinal center subtype with poor outcome. The germinal center subtype patients with isolated BCL2 translocations had significantly worse outcome than the patients without BCL2 rearrangements (P=0.0002), and their outcome was similar to that of patients with the activated B-cell subtype (P=0.30), but not as bad as the outcome of patients with double hit lymphoma (P<0.0001). Bcl-2 protein overexpression was associated with inferior outcome in patients with germinal center subtype lymphoma, but multivariate analysis showed that this was dependent on BCL2 translocations. The gene expression profiling of patients with BCL2 rearrangements was unique, showing activation of pathways that were silent in the negative counterpart. BCL2 translocated germinal center subtype patients have worse prognosis after rituximab-CHOP, irrespective of MYC status, but the presence of combined gene breaks significantly overcomes the prognostic relevance of isolated lesions.

Immunosuppressive and immunomodulatory therapy-associated lymphoproliferative disorders.

A variety of therapeutic agents may increase the risk of lymphoproliferative disorders/neoplasms. These include those agents used to treat other malignancies (i.e., cytotoxic chemotherapy) and those used to treat or prevent certain diseases (or graft rejection) that alter the immune system. This review is restricted to the secondary lymphoid disorders that are unrelated to primary DNA damage by cytotoxic chemotherapy, and thus will include discussions regarding post-transplant lymphoproliferative disorders and those lymphoproliferations associated with the therapy of autoimmune and other immune-mediated diseases. Three drugs, or classes of drugs, used in the treatment of autoimmune and other immune-mediated diseases are discussed in some detail. These include methotrexate, anti-metabolites (including thiopurines and mycophenolate mofetil), and immunomodulators. The appropriate recognition of these disorders is important in order to correctly classify and institute appropriate therapy, recognizing that reduced immunosuppression or withdrawal of therapy may be necessary, rather than treating as a malignant lymphoma.

Bone marrow B cell precursor number after allogeneic stem cell transplantation and GVHD development.

Patients without chronic graft-versus-host disease (cGVHD) have robust B cell reconstitution and are able to maintain B cell homeostasis after allogeneic hematopoietic stem cell transplantation (HSCT). To determine whether B lymphopoiesis differs before cGVHD develops, we examined bone marrow (BM) biopsies for terminal deoxynucleotidyl transferase (TdT) and PAX5 immunostaining early post-HSCT at day 30 when all patients have been shown to have high B cell activating factor (BAFF) levels. We found significantly greater numbers of BM B cell precursors in patients who did not develop cGVHD compared with those who developed cGVHD (median = 44 vs 2 cells/high powered field [hpf]; respectively; P < .001). Importantly, a significant increase in precursor B cells was maintained when patients receiving high-dose steroid therapy were excluded (median = 49 vs 20 cells/hpf; P = .017). Thus, we demonstrate the association of BM B cell production capacity in human GVHD development. Increased BM precursor B cell number may serve to predict good clinical outcome after HSCT.

Deep sequencing of the small RNA transcriptome of normal and malignant human B cells identifies hundreds of novel microRNAs.

A role for microRNA (miRNA) has been recognized in nearly every biologic system examined thus far. A complete delineation of their role must be preceded by the identification of all miRNAs present in any system. We elucidated the complete small RNA transcriptome of normal and malignant B cells through deep sequencing of 31 normal and malignant human B-cell samples that comprise the spectrum of B-cell differentiation and common malignant phenotypes. We identified the expression of 333 known miRNAs, which is more than twice the number previously recognized in any tissue type. We further identified the expression of 286 candidate novel miRNAs in normal and malignant B cells. These miRNAs were validated at a high rate (92%) using quantitative polymerase chain reaction, and we demonstrated their application in the distinction of clinically relevant subgroups of lymphoma. We further demonstrated that a novel miRNA cluster, previously annotated as a hypothetical gene LOC100130622, contains 6 novel miRNAs that regulate the transforming growth factor-ß pathway. Thus, our work suggests that more than a third of the miRNAs present in most cellular types are currently unknown and that these miRNAs may regulate important cellular functions.

Anaplastic large cell lymphoma: an unusual presentation in a 7-year-old girl.

Anaplastic large cell lymphoma (ALCL) accounts for 10% to 30% of all childhood lymphomas and approximately 5% of all non-Hodgkin's lymphoma. ALCL is considered to be a T-cell non-Hodgkin's lymphoma that can be divided into two major groups with distinct genetic, immunophenotypic, and clinical behaviors. The first group consists of a spectrum of CD30+ T-cell lymphoproliferative disorders that include primary cutaneous ALCL (C-ALCL) and lymphomatoid papulosis. The second group is systemic ALCL (S-ALCL), which is further divided into two subgroups: anaplastic lymphoma kinase positive (ALK+) and ALK-negative. Between 30% and 60% of S-ALCL express ALK, which is usually the result of a t(2;5) translocation that correlates with onset in the first three decades of life, male predominance, and good prognosis. Although morphologically similar, ALK- ALCL shows varied clinical behaviors and immunophenotypes; is commonly seen in older age groups, with a peak incidence in the sixth decade of life with no preference as to sex; and has an overall poorer prognosis. We present a case of CD30+, ALK- S-ALCL in a 7-year-old girl.

A case-control study of tobacco use and other non-occupational risk factors for lymphoma subtypes defined by t(14; 18) translocations and bcl-2 expression.

OBJECTIVE: We re-evaluated reported associations between tobacco use and other factors and non-Hodgkin lymphoma (NHL) t(14; 18)-subtypes based on fluorescence in situ hybridization (FISH) assays believed to be more sensitive than polymerase chain reaction (PCR), previously used for detecting t(14; 18). METHODS: Commercial FISH assays and bcl-2 immunostaining were performed on paraffin sections to determine t(14; 18) and bcl-2 case-subtypes. Polytomous logistic regression models estimated associations between NHL case-subtypes (versus 1,245 population-based controls) and tobacco use as well as other factors. RESULTS: Adjusting for age, state, and proxy status, t(14; 18)-negative NHL was associated with any tobacco use (vs. no tobacco use, OR = 1.9, 95% CI = 1.0-3.5), including current smoking (vs. no cigarette use, OR = 1.9, 95% CI = 1.1-3.2). Tobacco exposures were not clearly associated with t(14; 18)-positive NHL or bcl-2 case-subtypes. Hair-dye use and family history of a hemolymphatic cancer were associated with t(14; 18)-negative NHL, but the number of exposed cases was small. CONCLUSIONS: The association between t(14; 18)-negative NHL and cigarette smoking was unexpected given previous evidence of associations between smoking and follicular lymphoma (which is largely t(14; 18)-positive). Future studies characterizing additional molecular characteristics of t(14; 18)-negative NHL may help determine whether the association with smoking may have been causal versus an artifact of chance or bias.

p38 mitogen-activated protein kinase has different degrees of activation in myeloproliferative disorders and myelodysplastic syndromes.

The goal of the present study was to evaluate the activation patterns of p38 mitogen-activated protein kinase (MAPK) in myeloproliferative disorders (MPDs) and myelodysplastic syndromes (MDSs). Phosphorylated (activated) p38 MAPK was analyzed immunohistochemically in formalin-fixed decalcified bone marrow core biopsy specimens from 32 MPD, 33 MDS, and 11 control cases. Moderate p38 activation was commonly seen in MDS, whereas weak p38 activation was seen in all MPD cases and all control cases but 1 in the erythroid lineage. In myeloid and megakaryocytic lineages, strong p38 activation was more commonly observed in MDS compared with MPD (myeloid, 22/33 vs 2/32; P < .0001; megakaryocytic, 18/23 vs 5/32; P < .0001) and control (myeloid, 22/33 vs 2/11; P = .012; megakaryocytic, 18/23 vs 3/9; P = .035) cases. Furthermore, weak p38 activation was observed in myeloid and megakaryocytic lineages in MPD compared with control (myeloid, 15/32 vs 1/11; P = .033; megakaryocytic, 16/32 vs 0/9; P = .007) cases. Increased p38 MAPK activation may have a role in inhibiting hematopoiesis leading to cytopenias in MDS, and relatively decreased p38 activation in MPD might promote hematopoiesis, resulting in cytosis.

Reaction patterns of TRAP and DBA.44 in hairy cell leukemia, hairy cell variant, and nodal and extranodal marginal zone B-cell lymphomas.

CONTEXT: The differential diagnosis of hairy cell leukemia (HCL) includes HC variant (HC-V) and marginal zone lymphoma (MZL). There is a high sensitivity of combined DBA.44/TRAP-positivity (+) in confirming HCL. A previous study of mucosa-associated lymphoid tissue lymphoma showed DBA.44+ in 10%, TRAP+ in 29%, and DBA.44+/TRAP+ in 5%. OBJECTIVE: We now study nodal MZL (NMZL) and HC-V. DESIGN: Two HCL, 2 HC-V, 3 MZL of bone marrow (BM), 2 MZL versus B-cell lymphoma, not otherwise specified (BCL, NOS) of BM, and 4 NMZL and 5 extranodal MZL (EMZL) were stained with DBA.44 and TRAP and reviewed for staining pattern/intensity. RESULTS: DBA.44 intensely stained all cells in 2/2 HCL, 1/2 HC-V, and 1 EMZL; intensely stained >20% of neoplastic cells (NCs) in 7 MZLs (1 BM, 3 NMZL, and 3 EMZL); and was negative/stained <10% of NCs in 1/2 HC-V, the remaining MZLs (2 BM, 1 NMZL, and 1 EMZL), and 2/2 MZL versus BCL, NOS-BM. TRAP intensely stained all cells in 2/2 HCL, the DBA.44+ HC-V, and 1 MZL versus BCL, NOS-BM; intensely stained >20% of NCs in 1 MZL versus BCL, NOS-BM, 1 MZL-BM, and 1 EMZL; and was negative in the remainder (1 HC-V, 2 MZL-BM, 1 MZL vs. BCL, NOS-BM, the 4 NMZL, 3 EMZL) in which it was able to be performed. There was combined DBA.44+/TRAP+ in 2/2 HCL, 1/2 HCV, 1/3 MZL-BM, and 1/5 EMZL. Only 1 case (MZL vs. BCL, NOS-BM) was TRAP+/DBA.44-. CONCLUSIONS: Although combined intense, diffuse TRAP+/DBA.44+ is highly sensitive for HCL, it is not entirely specific, and may be observed in HC-V and EMZL, further supporting a histogenetic relationship between these entities.

Recommended curriculum for teaching hematopathology to subspecialty hematopathology fellows.

The performance and interpretation of clinical hematology and hematopathology laboratory tests and diagnosis of benign or malignant hematolymphoid disorders present unique challenges to hematopathology fellow trainees. To assist hematopathology fellowship program directors in preparing trainees to meet these challenges, a task force of pathologists with expertise in hematopathology developed a suggested training curriculum that includes a comprehensive list of topics in the areas of analytic hematology, bone marrow pathology, lymph node pathology, splenic pathology, lymphoma diagnostics, cytogenetics, and molecular diagnostics. This report also includes recommendations for training experiences that will facilitate the transition of subspecialty residents to practicing consultants in hematopathology.

Correlation of plasma cell percentages by CD138 immunohistochemistry, cyclin D1 status, and CD56 expression with clinical parameters and overall survival in plasma cell myeloma.

CONTEXT: Plasma cell myelomas (PCMs) are traditionally diagnosed by the percentage (%) of plasma cells (PCs) in the bone marrow aspirate differential combined with clinical parameters and radiographic findings. PCs are most reliably quantitated in bone marrow (BM) tissues by CD138 immunohistochemistry (IHC). However, there are no correlations of % CD138+ cells with clinical parameters or overall survival (OS). The presence of cyclin D1 has correlated with worst prognosis, but cyclin D1 has not been correlated with routine cytogenetics. CD56+, although not significantly reported in reactive plasmacytoses, monoclonal gammopathy of undetermined significance (MGUS), nor in lymphoplasmacytic lymphomas (LPLs), has not been evaluated in borderline diagnostic (borderline) cases. OBJECTIVES: It includes: (1) correlating the percentages of PCs by CD138 IHC, cyclin D1 status, and CD56 expression with clinical parameters and OS in PCMs, (2) correlating cyclin D1 status with routine cytogenetics in PCMs, borderline cases, and MGUSs, and (3) analyzing CD56 expression in PCMs, borderline cases, MGUSs, and LPLs. DESIGN: Bone marrow aspirates, BM touch preparations, and BM clot and/or biopsy sections with CD138/kappa/lambda IHC (44-PCMs, 9-MGUSs, 17-borderline cases, 3-LPLs, and 3-reactive plasmacytoses) were reviewed and stained with CD56 and cyclin D1. RESULTS/CONCLUSIONS: Increased CD138+ cells did not correlate significantly with clinical parameters or OS. Cyclin D1+ did not correlate with the presence of a t(11;14) by routine cytogenetics [although detected in all t(11;14)+ cases], clinical parameters, nor OS. CD56 expression was identified in PCMs, MGUSs, and LPL but not in reactive plasmacytoses. CD56+ did not distinguish PCMs, MGUS, and LPLs, and did not correlate with clinical parameters or OS. CD56 and cyclin D1 IHC were better evaluated in BM clot than biopsy sections.

Analysis of immunohistochemical markers in bone marrow sections to evaluate for myelodysplastic syndromes and acute myeloid leukemias.

BACKGROUND: Accurate bone marrow (BM) blast counts (BCs) are essential for diagnosis (dx) of myelodysplasia (MDS), MDS/myeloproliferative (MDS/MPD) disease, or acute myeloid leukemia (AML), and may be difficult in hemodiluted bone marrow aspirates (BMAs). Erythroid precursors (EPs) may be indistinguishable from myeloblasts in BM sections (aspirate clots/cores). We compare the usefulness of immunohistochemistry (IHC) [ie, CD34, CD117, myeloperoxidase (MPO), Hemoglobin A1 (HbA1), and terminal deoxynucleotidyl transferase (TdT)] of BM sections (IHC-BM) with BMA, bone marrow touch preparation (BMTP), and flow cytometry (FC) BCs. DESIGN: The initial BC (48), percentage (%) of Eps (38) (both based on initial 100 to 600-cell counts), and FC expressions of CD34, CD117, Glycophorin A(GLY A), and TdT (44) were tabulated from 50 BMs (MDS, MDS/MPD, or AML). BMAs (48) and BMTPs (25) subsequently received 500-cell counts. IHC-BM was performed (45:formalin, 5:B5-fixed) [CD34 (46), CD117 (45), HbA1 (45), TdT (42), and MPO (45)]. RESULTS: Retrospective BMA BCs revealed a 31% (15/48) discrepant rate between the original/retrospective BMA BCs; 80% revealed an underestimated initial BC. There was a 28% discordance rate between the retrospective BMA and BMTP reviews; 77% showed a higher BMTP BC. IHC showed significantly higher BCs in 19% (9/47), resulting in a different dx (5). However, CD34 and CD117 IHCS revealed lower BCs in 38% and 48%, respectively. The CD34 IHC results were primarily due to CD34-negative blasts by FC. The CD117 IHC results were largely unexplained. EPs were CD34 and CD117-negative. CONCLUSIONS: (1) Evaluation for MDS/AML requires 500-cell counts of BMAs and/or BMTPs. (2) CD34 and/or CD117 blasts by FC indicate IHC-BM may increase BC accuracy. (3) CD34 is more reliable than CD117 by IHC; however, in combination, they are most reliable and should be performed on BM clots/cores due to variable reactivity.

Acute liver failure due to natural killer-like T-cell leukemia/lymphoma: a case report and review of the literature.

Acute liver failure (ALF) is a medical emergency requiring immediate evaluation for liver transplantation. We describe an unusual case of a patient who presented with ascites, jaundice, and encephalopathy and was found to have ALF due to natural killer (NK)-like T cell leukemia/lymphoma. The key immunophenotype was CD2+, CD3+, CD7+, CD56+. This diagnosis, which was based on findings in the peripheral blood and ascitic fluid, was confirmed with liver biopsy, and was a contraindication to liver transplantation. A review of the literature shows that hematologic malignancies are an uncommon cause of fulminant hepatic failure, and that NK-like T-cell leukemia/lymphoma is a relatively recently recognized entity which is characteristically CD3+ and CD56+. This case demonstrates that liver biopsy is essential in diagnosing unusual causes of acute liver failure, and that infiltration of the liver with NK-like T-cell lymphoma/leukemia can cause acute liver failure.

Two cases of acute myeloid leukemia with t(11;17) associated with varying morphology and immunophenotype: rearrangement of the MLL gene and a region proximal to the RARalpha gene.

This report describes 2 cases of acute myeloid leukemia (AML), which based on the WHO classification would be classified as AML with an 11q23 (MLL) abnormality, but with contrasting morphologic and immunophenotypic profiles. One case had monocytic features (morphologically and immunophenotypically) with a t(11;17)(q23;q21), a previously identified variant translocation in acute promyelocytic leukemia (APL). The second case had morphologic and immunophenotypic features of APL associated with a t(11;17)(q23;q25). In both cases, fluorescence-in-situ hybridization (FISH) analysis demonstrated that the 11q23 breakpoint involved the MLL gene, but RARalpha was not involved in the 17q breakpoints. These cases illustrate the importance of FISH analysis to confirm the presence of a particular recurring rearrangement.

Burkitt lymphoma arising in organ transplant recipients: a clinicopathologic study of five cases.

We report five cases of Burkitt lymphoma arising in organ transplant recipients. There were four men and one woman with a mean age of 35 years. All were solid organ recipients with three renal, one liver, and one double lung transplantation. The time interval between organ transplantation and lymphoma averaged 4.5 years. Patients typically presented with high-stage disease with generalized lymphadenopathy and bone marrow involvement. Histology showed classic Burkitt lymphoma or atypical variant/Burkitt-like morphology. C-MYC rearrangement, including three cases with immunoglobulin heavy chain and two cases with lambda light chain, and Epstein-Barr virus were detected in all the cases. Additional chromosomal abnormalities were present in two of three cases and p53 mutation was found in one of three cases. Aberrant genotype and phenotype were frequently encountered, including minor monoclonal or oligoclonal T-cell populations and undetectable surface immunoglobulin light chain expression. Four patients received antilymphoma regimens, with combination chemotherapy (three patients) and/or Rituximab (three patients), in addition to reduction of immunosuppression. All four patients achieved complete remission. We conclude that posttransplant Burkitt lymphoma represents a characteristic clinicopathologic entity and occurs later after transplantation. Genotypic and phenotypic aberrations are often present. Rituximab may be an effective alternative to conventional combination chemotherapy in the treatment of a posttransplant Burkitt lymphoma.

Relative contributions of enzyme cytochemistry and flow cytometric immunophenotyping to the evaluation of acute myeloid leukemias with a monocytic component and of flow cytometric immunophenotyping to the evaluation of absolute monocytoses.

We evaluated the contributions of enzyme cytochemical stains and flow cytometric immunophenotyping (FCI) data to detection of monocytic cells (MCs) in acute myelomonocytic and acute monocytic leukemias (AMMLs and AMoLs) and compared FCI findings in AMoL, chronic myelomonocytic leukemia (CMML), and normal peripheral blood (PB) and bone marrow (BM) monocytes to classify and evaluate absolute monocytoses (AMs). We reviewed 10 AMMLs and 6 AMoLs with a-naphthyl-acetate esterase (ANAE) and a-naphthyl-butyrate esterase stains and a complete FCI profile and compared FCI data for 6 AMoLs, 7 CMMLs, 2 AMs, and normal monocytes. We confirmed increased sensitivity of ANAE staining to FCI data in detecting MCs in AMML and AMoL. CD14 was insensitive for confirming MCs; other characteristic markers of MCs were absent or partially lost in AMML and AMoL. Aberrant expression of CD56 (detected in 50% of AMMLs and AMoLs), CD34, and CD117 indicated malignancy. The mature MCs of the CMMLs revealed variable FCI abnormalities (partial loss of CD13, CD14, and CD15; expression of CD56), as in the monoblasts of AMoL. These FCI abnormalities in morphologically mature MCs might indicate markers for CMML. AMs revealed FCI abnormalities, indicating clues to their correct classification as CMML.

Flow cytometric immunophenotyping in posttransplant lymphoproliferative disorders.

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, I 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.