Clinical, immunophenotypic, and genetic analysis of adult lymphomas with morphologic features of Burkitt lymphoma

A prompt distinction of Burkitt lymphoma (BL) versus diffuse large B cell lymphomas (DLBCL) has important clinical implications; however, this distinction can be difficult. We analyzed 74 adult gray zone and 10 reference pediatric BL using immunohistochemistry (Ki-67, CD10, bcl2, bcl6) and fluorescence in situ hybridization (FISH) for MYC, BCL2, and BCL6 breakpoints. Two algorithms for classification were followed: algorithm A used a two-step review by four hemato-pathologists and algorithm B a set of only biologic markers (Ki-67 > or = 90%, CD10+, bcl6+, bcl2-, MYC breakpoint+, BCL2 and BCL6 breakpoint-). Both algorithms categorized all reference cases as BL. In the adult group, algorithm A resulted in 21 adult BL and 52 DLBCL and algorithm B in 23 BL and 51 "non-Burkitt" lymphomas (nBL); 9 cases (12%) contained two different translocations and were categorized as nBL in algorithm B. Fifteen cases (20%) fulfilled the BL criteria of both algorithms. Although not considered as BL according to both algorithms, many other lymphomas showed nonetheless a phenotypic and/or genetic shift to BL. BL according to algorithm B was more homogeneous with respect to clinical presentation (gender and localization) than BL defined by algorithm A. Our data suggest that only a few cases of these gray zone lymphomas represent true de novo BL. Immunohistochemistry for Ki-67, CD10, and bcl2 with analysis of MYC and preferably also BCL2 and BCL6 may be advised as a marker panel for this diagnostic dilemma.     

Diffuse large B-cell lymphoma of bone: an analysis of differentiation-associated antigens with clinical correlation

Twenty-nine patients with diffuse large B-cell lymphomas presenting with bone involvement, including 18 localized primary bone lymphomas (group 1), 2 multifocal primary bone lymphomas (group 2), and 9 patients with extraskeletal disease at diagnosis (group 3), were studied. The tumors were subclassified according to the criteria of the WHO classification and evaluated by immunohistochemistry for expression of antigens associated with germinal center (GC) and non-GC stages of B-cell differentiation (bcl-6, CD10, MUM-1, VS38c, CD138, bcl-2, and CD44). The presence of a BCL-2/IgH gene rearrangement was investigated by polymerase chain reaction. All cases were characterized by similar clinicopathologic and morphologic features and had similarly good overall outcome. The patients (23 males, 6 females, median age 44 years) had tumors in long bones (14), axial skeleton (8), limb girdles (3), and multiple sites (4). Most tumors (24) were centroblastic, with multilobated cells in 12 cases. Almost half of the tumors (14 of 29, 48%) were bcl-6+CD10+ (GC-like), 9 of 29 cases (31%) were bcl-6+CD10- (indeterminate phenotype), and 6 of 29 cases (21%) were CD10-bcl-6- (post-GC like). The indeterminate phenotype was seen only in primary bone lymphoma. MUM-1 was frequently expressed in GC-like and non-GC-like categories. We found no evidence of plasmacytic differentiation by CD138, and VS38c immunoreactivity was distinctly rare (2 of 29 cases). CD44 was detected in 6 tumors, all CD10-. Bcl-2 was expressed by 70% of the tumors, but only 1 of 23 cases tested had a Bcl-2/JH rearrangement by polymerase chain reaction. A survival analysis showed that GC-like tumors had a longer overall survival duration compared with non-GC-like tumors (P = 0.0046). In conclusion, a GC-like immunophenotype characterizes roughly half of large B-cell lymphomas of bone and is associated with an improved survival.     

IG/MYC rearrangements are the main cytogenetic alteration in plasmablastic lymphomas

Plasmablastic lymphoma (PBL) is an aggressive lymphoma characterized by a terminally differentiated B-cell phenotype that usually occurs in the immunocompromised or elderly patients. Although the clinical and pathologic characteristics of these tumors have been defined, the genetic alterations involved in their pathogenesis are not well known. In this study, we have investigated the chromosomal alterations of MYC, BCL2, BCL6, MALT1, PAX5, and IGH loci using fluorescence in situ hybridization in 42 PBL and 3 extracavitary primary effusion lymphomas. MYC rearrangements were identified in 20 of 41 (49%) PBL and the immunoglobulin (IG) genes were the partners in most tumors. MYC rearrangements were more common in Epstein-Barr virus (EBV)-positive (14 of 19, 74%) than EBV-negative (9 of 21, 43%) tumors (P<0.05). No rearrangements of BCL2, BCL6, MALT1, or PAX5 were detected in any PBL but gains of these loci were observed in 31% to 41% of the cases examined. Twelve of the 40 PBL in which 3 or more loci could be investigated had multiple simultaneous gains in 3 or more loci. No differences in the survival of the patients according to MYC were observed but the 4 patients with the longest survival (>50?mo) had no or low number of gains (<3). No rearrangements of any of these loci were seen in the primary effusion lymphomas. In conclusion, PBL are genetically characterized by frequent IG/MYC translocations and gains in multiple chromosomal loci. The oncogenic activation of MYC in these lymphomas may be an important pathogenetic element associated with EBV infection.     

Clinicopathologic and genetic characterization of follicular lymphomas presenting in the ovary reveals 2 distinct subgroups

Most lymphomas arising in the ovary are diffuse large B-cell or Burkitt lymphomas. Follicular lymphomas of the ovary are rare, and their clinicopathologic features are incompletely understood. We investigated clinical, morphologic, immunophenotypic, and genetic features of follicular lymphomas initially diagnosed in the ovary in 16 women. We performed immunohistochemistry for CD20, CD3, CD10, BCL6, IRF4/MUM1, and BCL2 and interphase fluorescence in situ hybridization for translocations involving BCL2, BCL6, and IRF4. Clustering was performed on the basis of clinicopathologic and genetic variables using Cluster 3.0. Ages ranged from 42 to 73 years. Unsupervised hierarchical clustering analysis revealed 2 distinct groups of patients. One group (group A) included 7 cases, which were negative or weakly positive for BCL2 protein and lacked IGH@/BCL2 translocations (6 cases evaluable). Four patients were of grade 3A, and 3 patients were of grade 2. Four had stage IE disease with unilateral ovarian involvement (subgroup A(1)), and the stage was unknown in 3 patients (subgroup A(2)). The second group (group B) included 9 cases of low histologic grade, which strongly expressed BCL2 protein and had IGH@/BCL2 translocations (7 cases evaluable). Six patients had stage III/IV disease, 2 had stage II disease, and the stage was unknown in 1 patient. Although follow-up intervals were limited, patients with higher-grade/low-stage disease tended to have favorable outcomes. These data indicate 2 distinct types of follicular lymphomas presenting in the ovary: a low-grade/high-stage/BCL2-positive group and a higher-grade/low-stage/BCL2-negative group. This latter group likely has distinct biological and immunologic characteristics, as has been suggested for higher-grade/low-stage follicular lymphomas presenting at other extranodal sites.     

B-cell posttransplant lymphoproliferative disorders in heart and/or lungs recipients: clinical and molecular-histogenetic study of 17 cases from a single institution

BACKGROUND: Posttransplantation lymphoproliferative disorders (PTLDs) are heterogeneous lymphoid proliferations representing a major complication of solid organ transplant. This study details the clinicopathological and molecular features of 17 B-cell PTLDs observed in a single center series of 988 heart and/or lung transplant recipients. METHODS: Cases were classified according to World Health Organization lymphoma classification and tested for Epstein-Barr Virus (EBV), clonality, histogenetic phenotypic (CD10, Bcl-6, MUM1, CD138), and genotypic (immunoglobulin and BCL-6 genes somatic hypermutation) markers. RESULTS: This series of 17 PTLDs included: two B-cell monoclonal polymorphic PTLDs and 15 B-cell monomorphic PTLDs (13 diffuse large B-cell lymphomas [DLBCL] and 2 Burkitt lymphomas [BL]). EBV was detected in 9/17 cases. A monoclonal immunoglobulin variable (IGV) genes rearrangement was documented in 17/17 cases; IGV somatic hypermutation was found in 88% of cases, indicating a prevalent origin from germinal center (GC)-experienced B cells. Using immunophenotypic markers, three histogenetic profiles were identified: a) CD10/bcl-6/MUM1/CD138, mimicking GC B-cells; b) CD10-/bcl-6+/MUM1+/CD138-, reminiscent of B-cells at the latest phases of GC reaction; and c) CD10-/bcl-6-/MUM1+/CD138+/-, consistent with preterminally differentiated B-cells. CONCLUSIONS: Correlation between morphology, histogenesis, and EBV status demonstrated a high degree of homogeneity in the two GC-related groups, mostly including EBV-negative cases with BL and DLBCL-centroblastic features; the third group, consisting of post GC EBV-positive cases, was histologically less homogeneous, as it included polymorphic PTLDs and DLBCL with immunoblastic and anaplastic features. The EBV-negative cases with GC histogenetic phenotype showed a slightly better outcome; however, such less aggressive prognostic trend was not confirmed by statistical analysis.     

Impact of Epstein-Barr virus in monomorphic B-cell posttransplant lymphoproliferative disorders: a histogenetic study

The heterogeneity of the posttransplant lymphoproliferative disorders (PTLDs) is well recognized. However, in contrast to other immunodeficiency-associated lymphomas or diffuse large B-cell lymphomas in general, studies of the histogenetic spectrum of the large category of monomorphic B-cell cases have been more limited, produced conflicting results, and have paid little attention to the impact of Epstein-Barr virus (EBV). Therefore, 30 monomorphic B-cell PTLD from 27 patients were analyzed using EBER in situ hybridization for EBV and a panel of antibodies directed against CD20, CD3/bcl-6, CD10, MUM-1/IRF4, CD138, and bcl-2. The results were correlated with the histopathologic features and clinical outcome. All PTLD were CD20 with 23% CD10, 53% bcl-6, 67% MUM-1/IRF4, 13% CD138, 83% bcl-2 and 67% EBV. 30% of the PTLD had a germinal center (GC) profile (CD10, bcl-6, MUM-1/IRF4, CD138), 53% a "late GC/early post-GC" profile (CD10, bcl-6, MUM-1/IRF4, CD138), 13% a post-GC profile (CD10, bcl-6, MUM-1/IRF4, CD138) and 3% an indeterminate profile (all markers negative). EBV positivity was associated with MUM-1/IRF4 expression (P=0.005) and with a non-GC phenotype (P=0.01). All CD138 cases were EBV. The cases with a GC phenotype were the most likely to resemble transformed GC cells (P=0.023). No statistically significant survival differences could be documented between those with a GC versus non-GC phenotype. These results highlight the broad histogenetic spectrum of monomorphic B-cell PTLD. They demonstrate the association of EBV positivity with a non-GC phenotype and suggest that EBV PTLD are more like lymphomas that arise in immunocompetent individuals. The lack of a demonstrable correlation with survival may relate to the relatively small number of cases studied.     

KSHV-positive solid lymphomas represent an extra-cavitary variant of primary effusion lymphoma

Primary effusion lymphoma (PEL) is a unique form of non-Hodgkin lymphoma (NHL) associated with Kaposi sarcoma-associated herpesvirus (KSHV; HHV-8) that displays a distinct constellation of clinical, morphologic, immunologic, and molecular characteristics. Rare KSHV-containing immunoblastic lymphomas occurring in solid tissues have been described. Whether they represent part of the spectrum of PEL has not been determined. The morphologic, immunophenotypic, and molecular features of KSHV-positive solid lymphomas occurring in 8 HIV+/AIDS patients were systematically investigated and compared with those of 29 similarly analyzed PELs. The 8 KSHV-positive solid lymphomas were virtually indistinguishable from the 29 PELs based on morphology (immunoblastic/anaplastic), immunophenotype (CD45 positive; T cell antigen negative; CD30, EMA, CD138 positive; CD10, CD15, BCL6 negative) and genotype (100% immunoglobulin genes rearranged; no identifiable abnormalities in C-MYC, BCL6, BCL1, BCL2; and uniformly EBV positive). The only identifiable phenotypic difference was that the KSHV-positive solid lymphomas appeared to express B cell-associated antigens (25%) and immunoglobulin (25%) slightly more often than the PELs (<5% and 15%, respectively; P = 0.11 and P = 0.08, respectively). The clinical presentation and course of the patients who develop KSHV-positive solid lymphomas were also similar, except for the lack of an effusion and somewhat better survival (median 11 months vs. 3 months). However, the 3 KSHV-positive solid lymphoma patients alive without disease 11, 25, and 44 months following initial presentation were recently diagnosed patients and, unlike the other patients with KSHV-positive solid lymphomas, received anti-retroviral therapy. These findings strongly suggest that these decidedly rare KSHV-positive solid lymphomas belong to the spectrum of PEL. Therefore, we propose that the KSHV-positive solid lymphomas be designated extra-cavitary PELs.     

Primary cutaneous large B-cell lymphoma: the relation between morphology, clinical presentation, immunohistochemical markers, and survival

The histogenesis, morphology, immunophenotype, and clinical behavior of cutaneous large B-cell lymphomas (CLBCL) are largely a matter of controversy. We performed an investigation to determine whether CLBCL have features that differentiate them from other large B-cell lymphomas and whether CLBCL is itself a heterogeneous group. To this end, we reviewed the main characteristics of a series of 32 cases of LBCL found in the skin. We reviewed the clinical findings and paraffin sections of the tumors from these 32 patients. The immunohistochemical study performed included p53, MIB1, Bcl2, Bcl6, and CD10 markers. We carried out statistical analysis of these data (univariate and multivariate), seeking an association between the features of the tumors and clinical outcome, as defined by failure-free survival time. Only one patient died as a consequence of the lymphoma. Nevertheless, the accumulated probability of survival without failure at 48 months was 0.46. The number, type, and localization of the lesions were not associated with variations in either survival or failure-free survival. The expression of p53 was negative in this group of CLBCL, whereas Bcl-2 expression or localization in the lower leg did not relate to any other significant feature. Histologic examination of the cases disclosed three different groups: Grade III follicular lymphomas (FLs), monomorphous large B-cell lymphomas (LBCL type I), and LBCL with an admixed component of small B-lymphocytes (LBCL type II). Grade III FL (11 cases) tended to be found in the head and neck and showed CD10 expression in a majority of cases. A higher probability of lymph node relapses was associated with cases located in the head and neck and with CD10+ tumors. Cutaneous large B-cell lymphomas are indolent tumors, but follow an insidious course. Our data support the interpretation that CLBCL is a heterogeneous condition; comprises some LBCL derived from CD10+ germinal center cells which manifests more frequently as tumors in the head and neck region, with an increased probability of relapse in lymph nodes [1] and has some distinctive morphologic features. The existence of a component of small B-cells within the other CLBCL could lend support to the theory that some of these tumors, more than arise de novo, may have originated in preexistent small B-cell lymphomas, but no firm evidence of this is provided in this study.     

Cyclin D1-negative blastoid mantle cell lymphoma identified by SOX11 expression

SOX11 expression has been recently shown to be useful in the diagnosis of mantle cell lymphoma (MCL), including cyclin D1-negative MCL with typical morphology. We evaluated SOX11 expression pattern in B-cell non-Hodgkin lymphoma (B-NHL) subtypes to confirm specificity and used it as a feature to identify the first reported cases of cyclin D1-negative blastoid MCL. SOX11 expression was evaluated by immunohistochemistry in 140 cases of mature B-NHL, including 4 cases of suspected blastoid MCL that lacked cyclin D1 expression and 8 cases of CD5-positive diffuse large B-cell lymphoma (DLBL). In addition, 5 cases of B or T lymphoblastic lymphoma were included. Nuclear expression of SOX11 was found in cyclin D1-positive MCL (30/30, 100%) and in a case of cyclin D1-negative MCL with typical morphology. SOX11 was also expressed in Burkitt lymphoma (1/5, 20%) and lymphoblastic lymphoma (2/3 T-LBLs, 2/2 B-LBLs, overall 4/5, 80%), whereas all cases of DLBL (including CD5 DLBL) and other small B-NHL were negative. The 4 suspected cases of blastoid MCL were also SOX11. These cases had a complex karyotype that included 12p abnormalities. We confirmed prior reports that stated that SOX11 nuclear expression was a specific marker for MCL, including cyclin D1-negative MCL with typical morphology. To our knowledge, this is the first report regarding its use in identifying cases of cyclin D1-negative blastoid MCL. Routine use of SOX11 in cases of suspected CD5 DLBL might help identify additional cases of cyclin D1-negative blastoid MCL.     

Comprehensive Assessment and Classification of High-Grade B-cell Lymphomas

High-grade B-cell lymphomas (HGBCLs) are a heterogeneous group of neoplasms that include subsets of diffuse large B-cell lymphoma, Burkitt lymphoma, and lymphomas with features intermediate between diffuse large B-cell lymphoma and Burkitt lymphoma. Morphologically indistinguishable HGBCLs may demonstrate variable clinical courses and responses to therapy. The morphologic evaluation and classification of these neoplasms must be followed by further genetic and immunophenotypic work-up. These additional diagnostic modalities lead to a comprehensive stratification of HGBCL that determines the prognosis and optimal therapy. This article reviews the well-established and emerging biomarkers that are most relevant to the clinical management of HGBCL.     

Primary Diffuse Large B-Cell Lymphoma of the Oral Cavity: Germinal Center Classification

Primary lymphomas of the oral cavity are rare and the most frequent type is diffuse large B-cell lymphoma (DLBCL). Recently, several reports have highlighted the value of classifying DLBCL into prognostically important subgroups, namely germinal center B-cell like (GCB) and non-germinal center B-cell like (non-GCB) lymphomas based on gene expression profiles and by immunohistochemical expression of CD10, BCL6 and MUM-1. GCB lymphomas tend to exhibit a better prognosis than non-GCB lymphomas. Studies validating this classification have been done for DLBCL of the breast, CNS, testes and GI tract. Therefore we undertook this study to examine if primary oral DLBCLs reflect this trend. We identified 13 cases (age range 38–91 years) from our archives dating from 2003–09. IHC was performed using antibodies against germinal center markers (CD10, BCL6), activated B-cell markers (MUM1, BCL2) and Ki-67 (proliferation marker). Cases were sub-classified as GCB subgroup if CD10 and/or BCL6 were positive and MUM-1, was negative and as non-GCB subgroup if CD10 was negative and MUM-1 was positive. Immunoreactivity was noted in 2/13 cases for CD10, in 12/13 for BCL6, in 8/13 for MUM-1, and in 6/13 for BCL2. Therefore, 8/13 (58%) were sub-classified as non-GCB DLBCLs and 5/13 (42%) as GCB subgroup. All tumors showed frequent labeling with Ki-67 (range 40–95%). Four of the 8 patients with non-GCB subgroup succumbed to their disease, with the mean survival rate of 16 months. Two patients in this group are alive, one with no evidence of disease and another with disease. No information was available for the other 3 patients in this group. Four of the 5 patients in the GCB subgroup were alive with no evidence of disease and one patient succumbed to complications of therapy and recurrent disease after 18 months. In conclusion, our analysis shows that primary oral DLBCL predominantly belongs to the non-GCB subgroup, which tends to exhibit a poorer prognosis. These findings could allow pathologists to provide a more accurate insight into the potential aggressive behavior and poorer prognosis of these lymphomas.     

Genetic aberrations in primary cutaneous large B-cell lymphoma: a fluorescence in situ hybridization study of 25 cases

In contrast to nodal large B-cell lymphomas, recurrent chromosomal aberrations have been studied only in a small number of cases of primary cutaneous diffuse large B-cell lymphoma (PCDLBCL). We investigated 25 PCDLBCLs (classified according to the WHO-EORTC classification into PCDLBCL, leg-type, 8; and PCDLBCL, other, 17), using an interphase fluorescence in situ hybridization technique. All cases were analyzed for chromosomal aberrations commonly observed in nodal large B-cell lymphomas, including structural aberrations of the genes BCL2, BCL6, and c-MYC, and numerical aberrations of the chromosomes/genes 3, 7, 8, 11, 12, 13, 17, 18q, RB1, and p53. We observed genetic aberrations in 19 (76%) of 25 patients. The most frequent numerical aberrations were gains of chromosome 12 (7 of 25, 28%), 7 (5 of 25, 20%), 3 (5 of 25, 20%), 18q (3 of 25, 12%), 11 (3 of 25, 12%), X (3 of 25, 12%), and losses of chromosome/gene 17/p53 (3 of 25, 12%). BCL2, c-MYC, and BCL6 were rearranged with the IGH gene in 4 (16%), 1 (4%), and none (0%) of 25 cases, respectively. Most aberrations were homogeneously distributed among cases of PCDLBCL, leg-type and of PCDLBCL, other, cases located on the leg or at other body sites, cases with round and cleaved cell morphology, and Bcl-2+ and Bcl-2- cases. These results suggest that PCDLBCLs show similar chromosomal aberrations irrespective of classification, anatomic site, cell morphology, and Bcl-2 expression, and that many similarities between primary cutaneous and nodal diffuse large B-cell lymphomas can be observed.     

Cutaneous b-cell lymphomas of follicular and marginal zone types: use of Bcl-6, CD10, Bcl-2, and CD21 in differential diagnosis and classification

Cutaneous follicular lymphomas (FLs) and cutaneous B-cell lymphomas of extranodal marginal zone (MZL)/mucosal-associated lymphoid tissue (MALT) type may have morphologic overlap, despite the fact that they are thought to be of distinct derivation (germinal center vs. postgerminal center). The problem is compounded by the reported absence of bcl-2 expression by many cutaneous FLs, leading to speculation that cutaneous FL may be unrelated to nodal FL. The authors analyzed the expression of the germinal center-associated antigens bcl-6 and CD10 and of bcl-2 in 18 cutaneous B-cell lymphomas (10 FLs and eight MZLs), in relationship to CD21+ follicular structures, to clarify the relationship of nodal to cutaneous FLs and to explore the value of these antigens in differential diagnosis. The authors studied 10 cutaneous FLs (seven primary and three secondary) and eight MZLs (six primary and two secondary). The FLs (found in six men and four women age 45-75 years) involved the trunk (n = 3) and scalp, face and neck (n = 7). The MZLs (found in five women and three men age 34-81 years) involved the trunk (n = 4), face and neck (n = 2), and arm (n = 2). Immunostaining for CD21, bcl-6, CD10, and bcl-2 allowed the delineation of compartments within the tumors and yielded distinct patterns of staining in FL and MZL. In both follicular and interfollicular/diffuse areas of FL the neoplastic cells were bcl-6+ (10 of 10), often CD10+ (seven of 10, four of seven primary), and bcl-2+ (nine of 10, six of seven primary). Only three of seven cases (one of five primary) had bcl-2 rearrangement detectable by polymerase chain reaction. In the MZLs, the neoplastic B-cells were bcl-6-, CD10-, and bcl-2+ (eight of eight). Three patterns of CD21+ follicles were identified in MZL: reactive germinal centers, uniformly bcl-6+, CD10+, and bcl-2- (five of eight MZLs); colonized follicles, both bcl-6-, bcl-2+, and L26+ cells, and bcl-6+ and bcl-2- cells (five of eight MZLs); and expanded/colonized follicular dendritic cell meshworks, bcl-6- and bcl-2+ B cells with rare residual bcl-6+ and bcl-2- cells (four of eight MZLs). The authors conclude that cutaneous FLs express bcl-6 uniformly, usually express CD10 and bcl-2, and have a follicular pattern similar to nodal FL and consistent with a germinal center origin. The immunophenotype of cutaneous FL is distinct from that of cutaneous MZL, which is negative for bcl-6 and CD10. Colonized follicles in MZL, identified by CD21+ follicular dendritic cell meshworks, contained numerous bcl-6- and bcl-2+ B cells, and were readily distinguished from neoplastic follicles in FL. Conversely, CD21- interfollicular and diffuse areas in FLs contained bcl-6+ and CD10+ cells, which were not seen in diffuse areas of MZLs. Thus, the combination of bcl-2, bcl-6, and CD21 staining is useful for the distinction of cutaneous MZL from cutaneous FL.     

T-cell/histiocyte-rich large B-cell lymphoma: a heterogeneous entity with derivation from germinal center B cells

T-cell/histiocyte-rich large B-cell non-Hodgkin's lymphoma (THRLBCL) is an unusual morphologic variant of diffuse large B-cell lymphoma. We reviewed 30 cases of THRLBCL to evaluate its heterogeneity based on morphologic, immunophenotypic, and genetic features. Cases were classified according to the appearance of the large neoplastic B cells into three morphologic variants: 1) lymphocytic and histiocytic (L&H-like) (resembling the L&H cells of nodular lymphocyte predominance Hodgkin's lymphoma (14 cases); 2) centroblast (or immunoblast)-like (10 cases), and 3) Reed-Sternberg cell-like (resembling the neoplastic cells of classic Hodgkin's lymphoma) (6 cases). We used a panel of immunohistochemical stains, including those with specificity for germinal center B cells: CD20, CD79a, CD30, CD15, epithelial membrane antigen, BCL-2, BCL-6, and CD10. The /JH polymerase chain reaction assay was further performed to investigate a relationship to follicular lymphoma. The results were correlated with Epstein-Barr virus status as determined by staining for latent membrane protein and EBER-1 in situ hybridization. All cases were of B-cell immunophenotype with strong surface CD20 reactivity in the neoplastic large lymphoid cells, although CD79a was more inconsistently and weakly expressed (10 of 17). Nuclear positivity for the BCL-6 protein was detected in the tumor cells in 26 of 29 (90%) cases. However, differences in expression of other antigens were encountered in the histologic subtypes. Epithelial membrane antigen positivity, a feature often seen in nodular lymphocyte predominance Hodgkin's lymphoma, was observed in 11 of 30 (37%) cases and was most commonly seen in cases with L&H cell morphology (8 of 14; 57%). CD30 expression was observed in 9 of 30 (30%) cases but was most frequent in cases with Reed-Sternberg-like morphology (3 of 6 [50%]). CD10 expression was infrequent overall (3 of 29; 10%), with 2 of 3 positive cases identified in the centroblastic group. The overall rarity of positivity for CD10, BCL-2 (3 of 22; 13%), and -2 JH rearrangement (1 of 28; 4%) indicates a lack of connection to follicular lymphoma for all subtypes. The three cases that were negative for BCL-6 protein were LMP-1 positive and EBER-1 positive by in situ hybridization, and 2 of 3 had neoplastic cells with Reed-Sternberg-like morphology. These results demonstrate that although a large proportion of THRLBCL represent tumors of germinal center B cell derivation, they exhibit a diversity of morphologic and immunophenotypic features. A subset of THRLBCL may be related to nodular lymphocyte predominance Hodgkin's lymphoma. A small percentage show features closely resembling classic Hodgkin's lymphoma and could be considered a variant of grey zone lymphoma.     

Micronodular T-cell/histiocyte-rich large B-cell lymphoma of the spleen: histology,immunophenotype, and differential diagnosis

Occasionally, primary large B-cell lymphomas (LBLs) arising in the spleen present with a micronodular pattern involving the splenic white pulp but sparing the red pulp. Histologically, the nodules contain scattered large B cells in a background of numerous T cells and histiocytes. They can cause substantial difficulty in histologic diagnosis as the morphology can mimic reactive and inflammatory lesions as well as other lymphoid neoplasms. In this study, we examined the histology and immunophenotype of the micronodular T-cell/histiocyte-rich LBL (MTLBL) of the spleen with a view to establish the characteristics that may be helpful in diagnosis. Paraffin-embedded material from 17 cases of MTLBL was studied. Clinical features and histology were reviewed and immunohistochemistry was performed for immunoglobulins, CD20, CD79a, CD3, CD68, CD10, BCL6, BCL2, OCT-2, epithelial membrane antigen, CD30, CD138, and EBV markers. The median age of presentation was 56 years, and the most frequent presenting features were anemia and B symptoms. All cases showed a micronodular pattern of involvement. The tumor nodules comprised a mixture of numerous CD3+ T cells and CD68+ histiocytes and scattered large CD20+ B cells with immunoglobulin light chain restriction. They were positive for BCL6 and OCT2 but negative for CD10, CD138, and EBV markers. There was variable expression of epithelial membrane antigen, Bcl-2, and CD30. No follicle dendritic cell meshwork infrastructure underlying the nodules could be demonstrated by staining for CD21 or CD35 antigens. The prognosis was poor; seven of the 12 cases with follow-up were dead within 2 years. MTLBL is unique variant of T-cell/histiocyte-rich diffuse LBL, characterized by primary splenic presentation and a micronodular architecture. The main differential diagnoses include granulomatous inflammation, Hodgkin's lymphoma, follicular lymphoma, and peripheral T-cell lymphomas.     

CD10 and BCL-6 expression in paraffin sections of normal lymphoid tissue and B-cell lymphomas

In this study the authors explored the value of immunostaining for follicular center B-cell markers, BCL-6 and CD10, in paraffin sections as a tool for the differential diagnosis of B-cell lymphomas. The cases studied comprised reactive lymphoid hyperplasia (RLH; n = 19), follicular lymphoma (FL; n = 50), low-grade mucosa-associated lymphoid tissue (MALT) lymphoma (n = 24), mantle cell lymphoma (n = 19), splenic marginal zone lymphoma (n = 13), diffuse large B-cell lymphoma (DLBCL; n = 54), Burkitt's lymphoma (BL; n = 20), nodular lymphocyte predominance Hodgkin's disease (NLPHD; n = 16), and classic Hodgkin's disease (CHD; n = 13). In RLH, CD10 and BCL-6 were expressed almost exclusively by the follicular center cells. In contrast in FL, the expression of CD10 (39/50) and BCL-6 (34/36) was seen in both follicular and interfollicular neoplastic B cells. Marginal zone/MALT lymphomas and mantle cell lymphoma were always negative. In DLBCL the expression was variable for both CD10 (21/54) and BCL-6 (39/47), with some tumors, including cases of transformed follicular lymphoma (9/10), coexpressing CD10 and BCL-6, and others expressing only BCL-6, and a small group expressing neither marker, possibly reflecting the underlying primary pathogenetic events such as the rearrangement of BCL-2 or BCL-6 genes. BL was always both CD10 and BCL-6 positive. In NLPHD the L&H cells expressed BCL-6 (11/13) but not CD10, whereas in CHD BCL-6 expression was seen in half of the cases. This study demonstrates that both CD10 and BCL-6 are reliable markers of follicular center B-cell differentiation. CD10 and BCL-6 immunostaining have an important role in differential diagnosis of FL from RLH and other low-grade B-cell lymphomas. The results also suggest that a CD10/BCL-6 expression pattern may be helpful in identifying main subsets of DLBCL. However, additional studies comparing genotype with immunophenotype are required.     

Primary bone marrow lymphoma: an uncommon extranodal presentation of aggressive non-hodgkin lymphomas

Bone marrow involvement by lymphoma is considered a systemic dissemination of the disease arising elsewhere, although some tumors may arise primarily in the bone marrow microenvironment. Primary bone marrow lymphoma (PBML) is a rare entity whose real boundaries and clinicobiological significance are not well defined. Criteria to diagnose PBML encompass isolated bone marrow infiltration, with no evidence of nodal or extranodal involvement, including the bone, and the exclusion of leukemia/lymphomas that are considered to primarily involve the bone marrow. Twenty-one out of 40 lymphomas retrospectively reviewed by the International Extranodal Lymphoma Study Group from 12 institutions in 7 different countries over a 25-year period fulfilled the inclusion criteria. These cases comprised 4 follicular lymphomas (FLs), 15 diffuse large B-cell lymphomas (DLBCLs), and 2 peripheral T-cell lymphomas, not otherwise specified. The FL cases showed paratrabecular infiltration, BCL2 protein and CD10 expression, and BCL2 gene rearrangement. DLBCL showed nodular infiltration in 6 cases and was diffuse in 9 cases; it also showed positivity for BCL2 protein (9/10) and IRF4 (6/8). Median age was 65 years with male predominance. All but 3 FL patients were symptomatic. Most cases presented with cytopenias and high lactate dehydrogenase. Four patients (3 FL cases and 1 DLBCL case) had leukemic involvement. Most DLBCL patients received CHOP-like or R-CHOP-like regimens. The outcome was unfavorable, with a median overall survival of 1.8 years. In conclusion, PBML is a very uncommon lymphoma with particular clinical features and heterogenous histology. Its recognition is important to establish accurate diagnosis and adequate therapy.     

Clinicopathologic Features of B-Cell Lineage Neoplasms With Aberrant Expression of CD3: A Study of 21 Cases

CD3 expression by immunohistochemistry was historically considered restricted to T-lineage or NK-lineage neoplasms but recently has been reported in rare cases of mature B-cell neoplasms, frequently in association with Epstein-Barr virus. Here, we describe the pathologic features of 21 B-cell lineage neoplasms that express CD3 protein by immunohistochemistry: 12 diffuse large B-cell lymphomas (DLBCLs); 2 plasmablastic lymphomas (PBLs); 4 plasma cell neoplasms; 2 Burkitt lymphomas; and 1 nodal follicular lymphoma, grade 3A. CD20 expression was negative or only partially positive in 13/21 cases. Epstein-Barr virus was positive in 3/20 tested cases (2 PBLs and 1 DLBCL). All tested neoplasms (14/14) had clonal immunoglobulin gene rearrangements, and no clonal T-cell gene rearrangements were detected (0/14). The 12 DLBCLs segregated into 2 main groups: 7 demonstrated features of plasmacytic differentiation but did not meet criteria for PBL, and 5 had anaplastic features. In addition to morphology, other features shared among the DLBCLs with plasmacytic differentiation, the plasma cell neoplasms, and the PBLs included extranodal presentation, cytoplasmic localization of CD3, and lack of expression of other T-cell antigens in most cases. In contrast, DLBCLs with anaplastic features and the single follicular lymphoma coexpressed multiple T-cell antigens in a predominantly membranous pattern and presented with nodal disease in a relatively younger patient population. Our data expand the spectrum of morphologic, phenotypic, and clinical features of B-cell neoplasms aberrantly expressing CD3. As these neoplasms often lack typical expression of B-cell antigens, knowledge of these features will help avoid misclassification.     

Diagnosis of Burkitt Lymphoma and Related High-Grade B-Cell Neoplasms

Burkitt lymphoma (BL) is an aggressive B-cell neoplasm with an extremely short doubling time that mainly affects children and young adults. Despite having several characteristic features, none is entirely specific for BL and the differential diagnosis may include diffuse large B-cell lymphoma (DLBCL), B lymphoblastic leukemia/lymphoma, and B-cell lymphoma unclassifiable with features intermediate between DLBCL and BL. We outline a practical approach to establish a diagnosis of BL and distinguish it from other high-grade B-cell malignancies. We pay particular attention to B-cell lymphomas with features intermediate between DLBCL and BL, a new diagnostic category in the 2008 World Health Organization classification system that provides a framework for categorizing challenging cases not meeting diagnostic criteria for either “classic” BL or DLBCL.