Bcl-6 protein expression by follicle center lymphomas. A marker for differentiating follicle center lymphomas from other low-grade lymphoproliferative disorders

The Comparative Diagnostic Features of Canine and Human Lymphoma

The non-Hodgkin lymphomas (NHLs) are a heterogeneous family of lymphoid malignancies that are among the most common neoplasms of both dogs and humans. Owing to shared molecular, signaling, incidence, and pathologic features, there is a strong framework supporting the utilization of canine lymphoma as a comparative, large animal model of human NHL. In alignment with the biologic similarities, the current approach towards the diagnosis and classification of canine lymphoma is based upon the human World Health Organization guidelines. While this approach has contributed to an increasing appreciation of the potential biological scope of canine lymphoma, it has also become apparent that the most appropriate diagnostic philosophy must be multimodal, namely by requiring knowledge of microscopic, immunophenotypic, and clinical features before establishing a final disease diagnosis. This review seeks to illustrate the comparative similarities and differences in the diagnosis of canine lymphoma through the presentation of the microscopic and immunophenotypic features of its most common forms.

Molecular genetic analysis of haematological malignancies II: mature lymphoid neoplasms

Molecular genetic techniques have become an integral part of the diagnostic assessment for many lymphomas and other chronic lymphoid neoplasms. The demonstration of a clonal immunoglobulin or T cell receptor gene rearrangement offers a useful diagnostic tool in cases where the diagnosis is equivocal. Molecular genetic detection of other genomic rearrangements may not only assist with the diagnosis but can also provide important prognostic information. Many of these rearrangements can act as molecular markers for the detection of low levels of residual disease. In this review, we discuss the applications of molecular genetic analysis to the chronic lymphoid malignancies. The review concentrates on those disorders for which molecular genetic analysis can offer diagnostic and/or prognostic information.

Mantle cell lymphoma in Taiwan: clinicopathological and molecular study of 21 cases including one cyclin D1-negative tumor expressing cyclin D2

Mantle cell lymphoma (MCL) is a rare B-cell lymphoma that has never been characterized in Taiwan. The purpose of the present paper was to retrospectively identify 21 cases in male patients, with a median age of 61, involving lymph node (91%), marrow (71%), and peripheral blood (23%). Eighteen (86%) were in stages III/IV with 1 and 5 year survival rates of 78% and 17%, respectively. Mixed nodular and diffuse pattern (45%) was most common while interstitial pattern (92%) predominated in marrow. Eighteen (86%) were of classical morphology, two were pleomorphic and one was blastic. The tumors expressed IgM and bcl-2 (100%), cyclin D1 (95%), CD5 (86%), CD43 and IgD (62%), CD52 (60%), and bcl-6 (5%). Ki-67 index>or=30% (P=0.1834) was associated with a trend toward poorer survival while p21, p27, or p53 expression was not statistically significant for survival. Real-time polymerase chain reaction for cyclin D1 (CCND1) gene mRNA expression showed high levels in nine cyclin D1-positive patients and a low level in the single cyclin D1-negative patient. The latter patient was cyclin D2 positive and negative for immunoglubuin heavy chain gene and CCND1 gene translocation by locus-specific interphase fluorescent in situ hybridization. In conclusion, it is confirmed that the usual morphological variants and aberrant immunophenotype of MCL in the West occur in Taiwan and that this disease carries a poor prognosis.

Prognostic significance of PU.1 in follicular lymphoma

Very few prognostic factors are known in follicular lymphoma (FL), a common malignancy of germinal centre (GC) B-cells. The Follicular Lymphoma International Prognostic Index (FLIPI) thus far appears to be the most important predictor of clinical outcome. This study explores the predictive power of the degree of GC differentiation for outcome in FL. Samples from 73 patients with FL were evaluated by immunohistochemistry for expression of GC markers. Strong PU.1, CD20, and CD75 expression were significantly associated with longer progression-free survival (PFS) and overall survival (OS). Results for PFS were independent of the International Prognostic Index or the Italian Lymphoma Intergroup prognostic index for CD75 and PU.1, but only PU.1 expression was independent of FLIPI for PFS and OS. Oct-2 was weakly expressed overall, but more strongly in higher grades of FL; it had a trend for negative linear association with PU.1 and strong positive linear association with CD27, which possibly reflects its role in terminal B-cell differentiation. We show that the level of GC differentiation, as determined by the levels of PU.1, CD75, CD20, Bcl-6, and CD10 expression, has an association with outcome in patients with FL. While this is determined qualitatively in most studies of diffuse large B-cell lymphoma, in FL there is a quantitative positive association between a high level of expression of GC antigens and longer OS and PFS even when data are stratified by the FLIPI score.

Contribution of Immunohistochemistry to Small B-Cell Lymphoma Classification

Although the small B-cell lymphomas show major morphologic overlapping, they have been recently shown to be distinct entities with several biologic and clinical differences. Therefore, the utility of a panel of paraffin-reactive antibodies in differentiating these neoplasms was investigated. Using clinical data and morphologic criteria, 134 cases of small B-cell lymphomas were grouped as those with (1) one strongly suggested diagnosis, (2) differential diagnosis between two types of lymphomas, and (3) small B-cell lymphoma without hints for further subclassification. With a panel of antibodies including CD5, CD10, CD23, CD43, bcl-2, and cyclin D1, most but not all cases could be precisely categorized. This panel confirmed the diagnosis in 96.5% of the cases from group 1. In group 2 it confirmed one of the two diagnoses in 81.5% of the cases. In group 3 it established a definitive diagnosis in 55% of the cases. When all groups were considered, a correct diagnosis could be established for 88.1% of cases; for 6.7% of them the authors remained with two possible diagnosis, and the broad "small B-cell lymphoma" was the only diagnosis for 5.2% of cases. CD10 separated most follicular lymphomas from other small B-cell lymphoid neoplasms. CD23 separated small lymphocytic lymphoma/chronic lymphocytic leukemia. Cyclin D1 separated mantle cell lymphoma. The present study selected CD10, CD23, and cyclin D1 as a minimal panel for the classification of small B-cell lymphomas, yielding a final diagnosis in 88.1% of the cases.

Grading follicular lymphoma on fine-needle aspiration specimens-A practical approach

Fine-needle aspiration biopsy (FNA) is a useful tool for evaluating and staging follicular lymphoma (FL) without subjecting patients to multiple excisional biopsies. The relative lack of architecture in FNA is a limitation in grading FL. Recognizing the various cellular components in aspirates of FL, correlating with flow cytometry, using other ancillary tests, and preparing cell blocks can help overcome difficulties in the grading process. Understanding the clinical relevance of distinguishing the various grades of FL is important in determining whether an aspiration biopsy is adequate or whether additional sampling by surgical biopsy is indicated.

Single nucleotide polymorphism in 5'-flanking region of BCL6 is not associated with increased risk of non-Hodgkin's lymphoma

Mutations in the 5'-regulatory region of BCL6 were suggested to play a role in non-Hodgkin's lymphoma (NHL) progression and in the transformation of follicular lymphoma to more aggressive diffuse large B-cell type. The aim of this study was to explore association between polymorphism G397C in the 5'-region of BCL6 and both incidence and progression of NHL in 154 NHL cases and 362 controls. Neither frequencies of the rare BCL6 allele 397C nor particular genotypes differed significantly between NHL cases and controls. There was no significant association of histological type of NHL and clinical characteristics with this polymorphism.

The pattern and frequency of t(14;18) translocation and immunophenotype in Asian follicular lymphoma

AIMS

Follicular lymphoma is frequently associated with t(14;18)(q32;q21) translocation. This study was undertaken to determine the pattern of Bcl-2, CD10 and Bcl-6 expression in relation to t(14;18) translocation in follicular lymphoma from a cohort of a multi-ethnic Asian population.

METHODS AND RESULTS

Sixty-two cases of follicular lymphoma were retrieved for immunohistochemistry, and t(14;18) translocation analysis by polymerase chain reaction and fluorescent in-situ hybridization techniques. Bcl-2 expression was present in 74% of the cases. CD10 expression was also relatively low (61%), with decreasing frequency of expression in high-grade tumours. Bcl-6 protein was expressed in most of the tumours (88%) regardless of the tumour grade. The t(14;18) translocation was detected in 46 cases (74%) with an extremely high rate of t(14;18) translocation in ethnic Indian cases (100%).

CONCLUSION

The frequency of t(14;18) translocation in this series of follicular lymphomas was higher when compared with previous Asian reports, but in accordance with European and North American findings. CD10 expression is strongly associated with a t(14;18) translocation event, but the overall CD10 expression was relatively low, possibly due to the high proportion of high-grade tumours in the series. t(14;18) translocation was not associated with Bcl-2 or Bcl-6 expression.

Applications of Flow Cytometry and Immunohistochemistry to Diagnostic Hematopathology

Objective.—Diagnostic hematopathology depends on the applications of flow cytometric immunophenotyping and immunohistochemical immunophenotyping combined with the cytomorphology and histologic features of each case. Select cases may require additional ancillary cytogenetic and molecular studies for diagnosis. The purpose of this review is to focus on the applications of flow cytometric and immunohistochemical immunophenotyping of paraffin-embedded tissue to diagnostic hematopathology. Advantages and disadvantages of these techniques are examined.

Data Sources.—The literature is extensively reviewed (PubMed 1985–2003) with an emphasis on the most recent applications and those that are most useful clinically, both diagnostically and prognostically.

Study Selection.—Studies were selected based on statistically significant results in large studies with reported adequate clinical follow-up.

Data Extraction.—The methodology was reviewed in the selected studies to ensure reliable comparison of reported data.

Data Synthesis.—Flow cytometric immunophenotyping offers the sensitive detection of antigens for which antibodies may not be available for paraffin immunohistochemical immunophenotyping. However, paraffin immunohistochemical immunophenotyping offers preservation of architecture and evaluation of expression of some proteins, which may not be available by flow cytometric immunophenotyping. These techniques should be used as complimentary tools in diagnostic hematopathology.

Conclusions.—There are extensive applications of flow cytometric and immunohistochemical immunophenotyping to diagnostic hematopathology. As cytogenetic and molecular findings evolve in diagnostic hematopathology, there may be additional applications of flow cytometric and immunohistochemical immunophenotyping to this field of pathology.

Variability in immunophenotype in diffuse large B-cell lymphoma and its clinical relevance

Diffuse large B-cell lymphoma (DLBCL), the single largest category of lymphoma, is a clinically and biologically heterogeneous disease entity. Clinically, patients differ in their mode of presentation and respond variably to therapy. A combination of clinical parameters can be used to predict the patient's response to therapy and survival. The pathological variability of DLBCL is expressed in morphology, immunophenotype, cytogenetic and molecular genetic features. Numerous markers detectable by immunohistochemistry and linked to different aspects of tumour biology have been studied in DLBCL, including lineage-associated and immune markers, proliferation and apoptosis markers, cell adhesion molecules, and more recently stage-specific markers of B-cell differentiation. This review summarizes these studies in regard to their clinical significance and in the light of recent advances in our understanding of the molecular pathology and histogenesis of DLBCL.

Update in the pathologic features of mature B-cell and T/NK-cell leukemias

Modern diagnosis of mature B- and T-cell leukemias requires integration of morphologic, immunophenotypic, and molecular genetic features. This integrative approach has allowed more precise definitions of specific disease entities. This in turn provides better information for clinicians to select proper therapy and determine prognosis. The characteristic pathologic features of these disorders are reviewed.

Clinicopathologic analysis of ocular adnexal lymphomas: extranodal marginal zone b-cell lymphoma constitutes the vast majority of ocular lymphomas among Koreans and affects younger patients

The majority of ocular adnexal lymphomas (OAL) are primary marginal zone B-cell lymphomas (MALT lymphomas). The present study correlated the clinicopathological variables with the histologic subtypes by World Health Organization (WHO) classification with emphasis on MALT lymphomas in OALs of Koreans. There were 68 cases (31 males and 37 females), with a mean age of 45.9 years (range 7-89 years). Histologically, 61 MALT-type, 2 diffuse large B-cell (DLBCL), 2 mantle cell type (MCL), 1 anaplastic large-cell (ALCL), and 2 NK/T-cell lymphomas (NK/T-L) were counted among them. Fifty-seven were primary cases (P-OAL), and 11 were secondary cases (S-OAL). Nearly all P-OALs were MALT lymphomas (n = 56, 98%), with an exception of 1 MCL. Eleven S-OALs included 5 MALT type, 2 DLBCL, 1 ALCL, 1 MCL, and 2 NK/T-L. All MALT lymphoma patients were alive (n = 59) except for 2 after a mean duration of follow-up of 27.6 months (range: 0-108 months): one died of an unrelated cause and one died of recurrence. One non-MALT type P-OAL was alive with no evidence of disease (42 months). Of the 11 S-OAL, 4 had marrow involvement and 5 had progression or relapse outside the orbit. Compared with the other subtypes, MALT lymphoma was more likely to present with local disease (P = 0.001), achieve complete remission (CR) (0.022), and be alive at last follow-up (0.197), and less likely to experience recurrence (P = 0.06). In conclusion, OALs in Koreans are characterized by a preponderance of primary lymphomas over systemic lymphomas, striking predominance of MALT type lymphomas, and young age of occurrence. Histologic subtype by WHO classification has a significant correlation with the final outcome, with the most favorable outcome associated with OALs of the MALT type.

Splenic marginal zone lymphoma

Splenic marginal zone lymphoma (SMZL) is a specific low-grade small B-cell lymphoma that is incorporated in the World Health Organization classification. Characteristic features are splenomegaly, moderate lymphocytosis with villous morphology, intrasinusoidal pattern of involvement of various organs, especially bone marrow, and relative indolent course. Tumor progression with increase of blastic forms and aggressive behavior are observed in a minority of patients. Molecular and cytogenetic studies have shown heterogeneous results probably because of the lack of standardized diagnostic criteria. To date, no definitive therapy has been established. Therapeutic options include treatment abstention, splenectomy, splenic irradiation, and chemotherapy.

Guess what: Chronic 13q14.3+/CD5-/CD23+ lymphocytic leukemia in blood and t(11;14)(q13;q32)+/CD5+/CD23- mantle cell lymphoma in lymph nodes!

We report a case of a patient with two B-cell lymphoproliferative disorders: CD5(-)/CD23(+) B-cell chronic lymphocytic leukemia and CD5(+)/CD23(-) mantle cell lymphoma. These disorders were diagnosed simultaneously based on flow cytometry, immunohistochemistry, fluorescence in situ hybridization, and polymerase chain reaction-based molecular studies. The B-cell lymphocytic leukemia clone predominated in the blood and bone marrow, whereas the mantle cell clone predominated in lymph nodes.

Germinal centre-like versus undifferentiated stromal immunophenotypes in follicular lymphoma

Follicular dendritic cells (FDCs) in reactive germinal centres (GCs) show modulated expression of antigens indicative of step-wise maturation from more undifferentiated stroma. The present study compared the expression of FDC markers CD21, CD23, CD35, and chemokine CXCL13 and the stromal markers low-affinity nerve growth factor receptor (LNGFR) and CNA.42 in 35 follicular lymphoma (FL) cases with reactive lymphoic tissue. CXCL13 was expressed by follicular stroma in all FLs but most cases showed either partial (11/35 cases, 31%) or complete (10/35 cases, 29%) absence of other FDC antigens, most commonly CD23, followed by CD21 and CD35, with variable patterns of LNGFR and CNA.42 immunostaining. Only a minority of FL cases (14/35, 40%) showed stroma that resembled mature FDCs (CD23+, CD21+, CD35+) and these tumours were always associated with numerous intrafollicular T-cells, similar to reactive GCs. In the 25 FL cases that had identifiable extrafollicular tumour cells, the immunophenotype of follicular stroma showed the same variability but the extrafollicular stroma showed an absence of FDC markers, with the exception of frequent strong LNGFR staining. Stromal phenotypic changes in FL were not correlated with mean follicle size, percentage of diffuse growth, tumour mitotic rate or the proliferation index as determined by PCNA immunostaining. Serial biopsy specimens analysed in a subset of 15 patients showed either a stable stromal phenotype (seven cases, 47%) or loss of FDC antigens in tumour-associated stroma over time (seven cases, 47%). The GC-like subset of FLs, having both abundant intrafollicular T-cells and fully differentiated CD23+ FDCs, comprises a minority of FL cases that likely have different growth requirements from FLs that lack these features. The pattern of FDC antigen loss in stroma of FL is a readily assessable biological feature that appears independent of architectural growth pattern and may serve as a useful surrogate marker of tumour progression.

Immunohistochemical expression of CD10 and t(14;18) chromosomal translocation may be indicators of follicle centre cell origin in nodal diffuse large B-cell lymphoma

AIMS

Although diffuse large B-cell lymphoma is categorized as a distinct entity in the REAL classification of lymphomas, it represents a heterogeneous group of neoplasms. A subgroup is probably of follicle centre cell origin and may evolve from a pre-existing follicular lymphoma. The t(14;18) chromosomal translocation can be demonstrated in the majority of follicular lymphomas and the aim of this study was to investigate the prevalence of t(14;18) translocation in a series of de novo nodal diffuse large B-cell lymphomas. We correlated this with the immunohistochemical expression of CD10, bcl2 and bcl6, markers which are usually expressed by the neoplastic cells in follicular lymphomas. We also correlated these parameters with the presence or absence of p53 protein expression by the neoplastic cells.

METHODS AND RESULTS

Nodal diffuse large B-cell lymphomas (n=34) were stained immunohistochemically with monoclonal antibodies to CD10, bcl2, bcl6 and p53 (D07). Polymerase chain reaction (PCR) for the t(14;18) translocation was also performed. Fourteen, 24 and 29 (41%, 71%, 85%) cases exhibited positivity for CD10, bcl2 and bcl6, respectively. In 12 cases there was positivity with D07 (35%). By PCR, the t(14;18) translocation was identified in five cases (15%), four of which were positive for CD10 and bcl2 and all of which were positive for bcl6. One of five cases positive for the chromosomal translocation exhibited positivity with D07.

CONCLUSIONS

In this study the t(14;18) translocation was identified in 15% of diffuse large B-cell lymphomas, all but one of which exhibited positivity for CD10, bcl2 and bcl6. These may represent cases of follicle centre cell origin which may or may not have evolved from a pre-existing follicular lymphoma. It is possible that positivity for CD10 especially may identify cases which are of follicle centre cell origin and that the absence of t(14;18) translocation in some of these cases may reflect the fact that the translocation cannot normally be demonstrated in all follicular lymphomas. Whether the presence or absence of the translocation and the immunophenotype are prognostically important should be investigated further.

Proteins encoded by genes involved in chromosomal alterations in lymphoma and leukemia: clinical value of their detection by immunocytochemistry

Acquired chromosomal anomalies (most commonly translocations) in lymphoma and leukemia usually result in either activation of a quiescent gene (by means of immunoglobulin or T-cell-receptor promotors) and expression of an intact protein product, or creation of a fusion gene encoding a chimeric protein. This review summarizes current immunocytochemical studies of these 2 categories of oncogenic protein, with emphasis on the clinical relevance of their detection in diagnostic samples. Among the quiescent genes activated by rearrangement, expression of cyclin D1 (due to rearrangement of the CCND1 [BCL-1] gene) is a near-specific marker of t(11;14) in mantle cell lymphoma; BCL-2 expression distinguishes follicular lymphoma cells from their nonneoplastic counterparts in reactive germinal centers and appears to be an independent prognostic marker in diffuse large cell lymphoma; and TAL-1 (SCL) expression identifies T-cell acute lymphoblastic neoplasms in which this gene is activated. The protein products of other genes activated by chromosomal rearrangement have a role as markers of either lineage (eg, PAX-5 [B-cell-specific activator protein] for B cells, including B-lymphoblastic neoplasms), or maturation stage (eg, BCL-6 for germinal-center and activated B cells and MUM-1/IRF4 for plasma cells). Currently, no hybrid protein encoded by fusion genes is reliably detectable by antibodies recognizing unique junctional epitopes (ie, epitopes absent from the wild-type constituent proteins). Nevertheless, staining for promyelocytic leukemia (PML) protein will detect acute PML with t(15;17) because the microspeckled nuclear labeling pattern for PML-RARalpha is highly distinctive. Similarly, antibodies to the anaplastic lymphoma kinase (ALK) tyrosine kinase are valuable (because wild-type ALK is not found in normal lymphoid tissue) in detecting neoplasms (CD30-positive large T-cell lymphomas) with t(2;5) or its variants. Thus, immunocytochemical detection of the products of many rearranged genes in lymphoma and leukemia can be clinically informative and provide information on cellular and subcellular protein expression that cannot be inferred from studies based on messenger RNA.

Ovarian non-Hodgkin's lymphoma: a clinicopathologic study of eight primary cases

Primary (localized) non-Hodgkin's lymphoma (NHL) of the ovary is rare. We studied eight cases of primary ovarian NHL to better understand the clinicopathologic and immunophenotypic features of these tumors. The patients ranged in age from 29 to 62 years (mean 47 years). Pelvic complaints were the most common symptoms; however, three of eight neoplasms were discovered incidentally. All tumors were unilateral and Ann Arbor stage I(E). The three incidental NHL were microscopic (largest 1.2 cm), whereas the grossly evident lesions ranged from 7.5 to 20 cm (mean 13.3). Each tumor was classified according to the World Health Organization Classification as follows: diffuse large B-cell lymphoma (three cases), follicular lymphoma (two cases), Burkitt lymphoma (one case), T-cell anaplastic large cell lymphoma (one case), and precursor T-lymphoblastic lymphoma (one case). Six tumors were of B-cell lineage, and two tumors were of T-cell lineage. All three diffuse large B-cell lymphomas were positive for BCL-6, two were positive for CD10, and two were positive for BCL-2. Estrogen and progesterone receptors were negative in all NHLs assessed. Patients were treated by various combinations of surgery, chemotherapy, and radiotherapy. Clinical follow-up ranged from 1.3 to 11.7 years (mean 5.2) and all patients were alive without disease at last follow-up. We conclude that most patients with primary ovarian NHL present with symptoms attributable to an ovarian mass, but in a subset of patients ovarian NHL may be detected incidentally. With appropriate therapy, patients appear to have a favorable prognosis although follow-up is short for some patients in this study.

Angiotropic lymphoma: an immunophenotypically and clinically heterogeneous lymphoma

Angiotropic lymphoma (AL) is an uncommon lymphoma often presenting with nonspecific clinical features and having a high mortality rate. Although not specifically recognized by the Revised European-American Classification of Lymphoid Neoplasms, it likely will appear as a subtype of diffuse large B-cell lymphoma in the upcoming WHO classification. Some authors may also consider it to be a subtype of cutaneous lymphomas. Recent studies have reported an immunophenotypic heterogeneity of AL, and in rare instances, an association with other NHL. To further characterize AL, we studied the immunophenotype by immunohistochemistry for CD5, CD10, CD20, bcl-2, and bcl-6 in 18 cases of B-cell AL identified at three medical centers in North America. Bcl-2 gene rearrangement status by polymerase chain reaction and Epstein Barr virus status by in situ hybridization also were evaluated. Eight men and 10 women were identified with AL (median age 71 years). Eleven patients were diagnosed in life and seven were diagnosed at autopsy. Neurologic symptoms were the most common presentation, seen in six patients. Skin was the most commonly biopsied site. All showed classic intravascular localization; in two cases, there was also a minor diffuse large cell lymphoma component observed in some organs. Most (89%) of the cases expressed bcl-2 protein; CD10, bcl-6 and CD5 were each expressed in 22% of cases. Based on CD5 and CD10 expression, three major groups were evident: CD5-, CD10- (11 cases); CD5+, CD10- (3 cases), and CD5-, CD10+ (3 cases). Even though a follicle center lymphoma preceded the AL in one patient, we did not detect bcl-2 gene rearrangement in any of these cases. All cases were negative for Epstein Barr virus. Of the five treated with chemotherapy, two achieved a complete remission. Based on these findings, we conclude that ALs are clinically and immunophenotypically heterogeneous and may represent more than one pathogenetic entity. In some instances AL may be preceded by another lymphoproliferative disorder, raising the possibility that some cases of AL may represent a transformation from another type of lymphoma. Cutaneous manifestations of AL are common; however, it appears to be a systemic lymphoma. Although often fatal, patients with AL who are diagnosed early and treated with chemotherapy may achieve remission.

An immunophenotypic and molecular study of primary large B-cell lymphoma of bone

Primary non-Hodgkin's lymphomas of bone (PNHLB) is a rare form of extranodal lymphoma. Many studies have reported the clinical, radiologic, and histopathologic characteristics of PNHLB; however, their molecular features have not been well studied. In this report, we present the immunophenotypic and molecular characteristics of 20 primary large B-cell lymphoma (PLBCL) of bone from 20 adults. Most demonstrated centroblastic morphology, with the majority exhibiting nuclear multilobation. One case (5%) demonstrated anaplastic features with strong CD30 expression but was ALK-1 negative. BCL-6 expression was seen in 6 of 20 cases, and strong p53 protein expression was seen in 11 of 20 (55%) cases. The majority of cases analyzed (13/18 = 72%) demonstrated a clonal B-cell process by IgH gene rearrangement studies. Of the five cases that did not demonstrate a clonal population, two expressed BCL-6 protein. No cases demonstrated a bcl-2/JH rearrangement, but BCL-2 protein expression was seen in 11 of 20 (55%) cases. In summary, primary lymphoma of bone is largely a non-Hodgkin's lymphoma of large B-cell type. Our studies demonstrate that p53 and BCL-2 expression may play a role in the pathogenesis of PLCBL of bone. In addition, a subset of the cases are of putative germinal center B-cell origin based on the expression of BCL-6 protein and may be genetically distinct from follicle center lymphomas. The results provide evidence for molecular heterogeneity within primary large B-cell lymphomas of bone.

Expression of bcl-6 and CD10 in primary mediastinal large B-cell lymphoma: evidence for derivation from germinal center B cells?

Primary mediastinal large B-cell lymphomas (LBCLs) constitute a unique subtype of diffuse LBCLs, with distinct clinical, immunophenotypic, and morphologic features. These lymphomas are thought to originate from the thymus, and it has been hypothesized that they derive from a population of B lymphocytes normally present in the thymic medulla. Most diffuse LBCLs harbor somatic mutations in their immunoglobulin genes, suggesting that they have been exposed to the germinal center. To investigate the possible relationship of mediastinal LBCLs to germinal center B cells, we analyzed the expression of bcl-6 and CD10 in 19 mediastinal LBCLs, using an immunoperoxidase technique on formalin-fixed tissue. We found that 19 of 19 (100%) mediastinal LBCLs were bcl-6+ and 6 of 19 (32%) mediastinal LBCLs were CD10+. Because mediastinal LBCLs usually lack BCL-6 gene rearrangement or mutations, expression of bcl-6 and CD10 in these tumors tends to support a germinal center derivation.

Cutaneous follicle center lymphoma: a clinicopathologic study of 19 cases

Cutaneous follicle center lymphoma (FCL) is reported to have a unique immunophenotype and clinical course as compared with nodal FCL. We studied 19 cases of FCL of the skin using paraffin embedded tissue. An immunohistochemistry panel included CD45, CD3, CD20, CD43, CD21, bcl-2, bcl-6, CD5, and CD10. Molecular studies were performed by polymerase chain reaction for immunoglobulin heavy chain (IgH) and t(14;18). Trisomy 3 was performed by fluorescent in situ hybridization (FISH) in 13 cases. Follow up was obtained in 17 cases (range 3 to 137 months). Patients included 10 females and 9 males ranging in age from 33 to 88 years at first presentation (mean, 64). Twelve of 19 presented in the head and neck and 6 in the trunk and 1 on the arm. All had no known lymph node disease at presentation. Seventeen patients had no nodal disease with a minimum 3 month follow-up; 2/19 had unknown lymph node status with no follow-up. All cases were immunoreactive with CD20 and negative with CD3. Bcl-2 was immunoreactive in 11/18 cases, bcl-6 in 15/15, CD10 in 14/17, CD43 in 2/16 (both were CD10 immunoreactive) and CD5 in 1/15 (it was also bcl-6 immunoreactive). Eight of 18 cases were monoclonal for IgH. Three of 17 showed the presence of t(14;18). FISH was positive in 4 cases for trisomy 3 ranging from 16 to 22% (12% threshold). Follow-up showed no evidence of disease in 14/17 patients (4 to 137 mos). 3/17 patients are alive with disease (17 to 100 mo), and no patients died of disease.

Lymphoma immunophenotyping: a new era in paraffin-section immunohistochemistry

Recent advances in immunohistochemistry have made it possible to investigate lymphomas for the expression of a wide range of antigens in fixed tissues. Epitope retrieval, sensitive detection methods, and the availability of new monoclonal antibodies have all contributed to one's ability to perform detailed immunophenotyping that previously could only be done in cryostat sections or by flow cytometry. Current lymphoma classifications make use of characteristic immunophenotypic profiles that aid in the reproducible diagnosis and subcassification of these neoplasms. The following is a review of the current state of immunophenotyping for lymphoid neoplasms in fixed tissues.

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.

Paraffin immunoreactivity of CD10, CDw75, and Bcl-6 in follicle center cell lymphoma

Follicle center cell lymphoma(FCCL) has the following immunophenotype(IP): sIg+, Pan B+, CD10+/-, CD5-, CD23-/+, CD43-, CD11c-, CD25-. In addition, reactivities of a malignant lymphoma with CDw75(LN-1) and bcl-6 are considered indicators of FCCL. Bcl-6 expression is common in Grade 1 FCCL (100%) and rare in other indolent B-cell lymphomas(BCL). In contrast, bcl-2 expression is common in FCCL (80%) and in other BCL subtypes. Since no previous study has correlated paraffin immunoreactivity(PIR) of CD10, CDw75, and bcl-6 in FCCL (Grades 1-3), this is this study's purpose. Twenty-nine FCCL's were identified and reviewed (6, Grade 1; 10, Grade 2; 13, Grade 3) from the Division of Hematopathology, St. Louis University. The diagnoses were based on morphology and immunohistochemistry(IH)(21 cases) +/- the flow cytometric IP(14 cases). The paraffin blocks were stained for CD10 (Novacastra, Vector Laboratories, Burlingame, CA), CDw75 and bcl-6 (DAKO Corporation, Carpinteria, CA). Results showed that, CD10 by paraffin IH(PIH) was positive in 23 [18(strong); 3(moderate); 2(weak)] and negative in 6(3, Grade 2; 3, Grade 3). All CD10-cases were CDw75+; 4, bcl-6+. The two CD10-, bcl-6-cases were Grade 2. CDw75 was positive in 28 cases [16(strong); 11(moderate); 1(weak)] and negative in 1 (Grade 3; CD10+, bcl-2+, bcl-6+). Bcl-6 was positive in 26 [16(strong); 6(moderate); 4(weak)] and negative in 3(Grade 2's). Thus, the sensitivity of CD10, CDw75, and bcl-6 by PIH for FCCL was 79%, 97%, and 90%, respectively. Of the three stains evaluated by PIH in FCCL, CDw75 was the most sensitive, closely followed by bcl-6. CD10 was least sensitive-79%. By combining these 3 stains, the sensitivity was 100%; thus, a combined approach is recommended.

Immunophenotypic and genotypic markers of follicular center cell neoplasia in diffuse large B-cell lymphomas

Diffuse large B-cell lymphomas (DLBCL) are a biologically and clinically heterogeneous entity. Although some DLBCL represent transformation of follicular lymphomas (FL), the proportion that is of follicular center cell (FCC) origin remains uncertain. Immunophenotypic and genotypic markers used to suggest a FCC origin for a lymphoma (bcl-6 and CD10 expression, lack of CD138 expression, bcl-2 rearrangements [R]) or to subdivide DLBCL (bcl-2 expression, bcl-6 R) were therefore investigated in 22 FL and 44 DLBCL using paraffin section immunostains and Southern blot/polymerase chain reaction analysis. All FL tested were bcl-6+ (19) and CD138- (22) with 16/19 also bcl-2 and CD10+ (classic phenotype), one bcl2+, CD10- (grade III) and two bcl2-, CD10+ (grade II or III). Bcl-2R was identified in 4/5 FL-GrI, 3/6 FL-GrII, and 1/3 FL-GrIII. Bcl-6R was found in 0/5, 2/4, and 0/3 FL, respectively. All but 3/41 DLBCL were bcl-6+ with 17/37 also bcl-2+ and CD10+. Three of these cases were also CD138+. Twelve bcl-6+ cases were bcl-2+, CD10-, six bcl-2-, CD10+, and two bcl-2-, CD10-. The three bcl-6- cases were bcl-2+, CD138- and two were CD10+. Bcl-2R was identified in 5/27 DLBCL with 4/5 bcl-2+, 3/4 tested CD10+ and 4/4 bcl-6+. Bcl-6R was identified in 7/26 including three with a classic FL phenotype. The vast majority of DLBCL in this study have an immunophenotype that supports a FCC origin. Although the proportion of DLBCL that co-expressed bcl-6, CD10 and bcl-2 was lower than for the FL, absence of bcl-2 or CD10 may be associated with higher grade FL It is also possible that bcl-6 expression is not completely specific for a FCC origin. Only a minority of cases suggested postfollicular differentiation. Only a minority of DLBCL show bcl-2R, suggesting that many have a different molecular pathogenesis than most low-grade FL. Bcl-6R did not exclude a FCC origin.

Large B-cell lymphoma of thyroid. Two cases with a marginal zone distribution of the neoplastic cells

We report 2 cases of B-cell lymphoma of the thyroid in which although a marginal zone distribution of the neoplastic cells was present, the cytologic features of the cells indicated large cell lymphoma. One of the cases showed an accumulation of crystalline inclusions within the cytoplasm of the neoplastic cells. Many of these inclusion-bearing cells showed plasmacytoid features. By immunohistochemical studies performed on formalin-fixed paraffin-embedded tissue, both of the cases showed a B-cell phenotype as indicated by CD20 expression, and 1 showed kappa light chain restriction. In both cases, Ki-67 staining corroborated the impression of an aggressive neoplasm with staining of 50% and 90% of the tumor cells. Both patients received cyclophosphamide, doxorubicin, vincristine, and prednisone with radiation therapy, and both are without evidence of disease after 17 and 18 months of follow-up. It is important to recognize this pattern of large B-cell lymphoma of the thyroid gland. While the indolent course typical of most low-grade extranodal marginal zone lymphomas is not likely in these cases, the outcome may be favorable if patients are treated aggressively with therapy for large cell lymphoma.

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.

Clinicopathologic reassessment of primary cutaneous B-cell lymphomas with immunophenotypic and molecular genetic characterization

Primary cutaneous B-cell lymphomas (PCBLs) may have particular clinicopathologic characteristics distinct from their lymph node-based counterparts. It has been suggested that PCBLs should have a separate classification system. The aim of this study was to determine whether the Revised European-American Lymphoid Neoplasms (REAL) classification is applicable to PCBL. Thirty-nine cases of PCBL from 36 patients, consisting of 20 men and 16 women (median age 66 yrs), were included in this study. Paraffin-section immunohistochemistry for CD3, CD5, CD10, CD20, CD43, Bcl-2, Bcl-6, and cyclin D1 was performed in all cases. Immunostaining for immunoglobulin light chains was also performed on cases histologically diagnosed as extranodal marginal zone lymphoma (MZL) and primary cutaneous B-cell lymphoma unclassifiable (PCBLu). Polymerase chain reaction (PCR) analysis of t(14;18) was performed in all cases. Immunoglobulin heavy chain gene rearrangement (VDJ) was tested by PCR on all follicle center lymphoma (FCL), MZL, and PCBLu cases. The 39 cases consisted of 15 (39%) FCLs, 13 (33%) diffuse large B-cell lymphomas (DLCL), 9 (23%) extranodal MZL, and 2 cases of PCBLu. Anatomically, 59% of PCBLs occurred in the head and neck, of which approximately 57% were FCL. Five of six cases presenting on the lower extremity were DLCL. Follow-up data was available from all 39 patients with a mean of 50.8 months. All but two patients are alive with or without disease at last contact. One patient with DLCL died of lung metastases and the other DLCL patient died of sepsis as a complication of therapy. In all 15 cases of FCL, CD10 and/or Bcl-6 expression supported the follicle center origin of the neoplastic cells. In contrast to previous reports, we found that 53% (8 of 15) of primary cutaneous FCL had either Bcl-2 protein expression or t(14;18). Our data indicate that many cases of primary cutaneous FCL have Bcl-2 alterations similar to their nodal counterpart. We found that 95% (37 of 39) of PCBLs could be classified according to the REAL classification, supporting its applicability in cutaneous lymphomas.