Genetic analysis of de novo CD5+ diffuse large B-cell lymphomas suggests an origin from a somatically mutated CD5+ progenitor B cell

CD5+ diffuse large B-cell lymphoma: a narrative review

Diffuse large B-cell lymphoma (DLBCL) is a heterogeneous entity, and cell surface cluster of differentiation (CD) 5 expression may represent a distinct subset. Here, we provide a narrative review of CD5+ DLBCL to understand its clinical implications. Between 5-10% of DLBCL express CD5, making it an uncommon subset. Studies have variably shown that CD5+ DLBCL may be associated with increased age, high lactate dehydrogenase, B symptoms, extra-nodal sites, higher International Prognostic Index score, and advanced stage. CD5+ DLBCLs are more likely to express Bcl-2, MYC, and MUM1; a large proportion exhibit an activated B-cell (ABC)-like phenotype. The balance of studies generally supports an independent prognostic value of CD5 in DLBCL While more aggressive first-line regimens have been advocated for CD5+ DLBCL, including dose-adjusted R-EPOCH and autologous stem cell transplant, evidence to support these approaches is lacking; further study is warranted to identify the optimal treatment strategy for this disease entity.

CD5 expression correlates with inferior survival and enhances the negative effect of p53 overexpression in diffuse large B-cell lymphoma

De novo CD5-positive diffuse large B-cell lymphoma (CD5+ DLBCL) is increasingly recognized as a distinct pathologic phenomenon with a specific clinical picture. However, CD5+ DLBCL has not been studied on a large scale in China. In this study, we show that CD5+ DLBCL occurs at a low frequency (9.2%). Comparison of clinical characteristics of CD5+ vs CD5- DLBCL showed that CD5+ DLBCL was more frequently elderly (>60 years) and had B symptoms, high-performance status, stage III-IV, an IPI score >2 and bone marrow involvement. Patients with CD5+ DLBCL had tumours with a higher prevalence of BCL-2 and p53 overexpression than CD5- DLBCL. Patients with CD5+ DLBCL had inferior progression-free survival (PFS) and overall survival (OS) than did patients with CD5- DLBCL. For CD5+ DLBCL, the patients who were treated with rituximab showed significantly better PFS and OS than those treated without rituximab. However, patients treated with RCHOP showed similar PFS and OS when compared with the group treated with intensive therapy. In addition, patients with p53 and CD5 co-expression had the worst PFS and OS. In conclusion, CD5+ DLBCL was associated with unfavorable clinicopathologic variables and with inferior survival. CD5+ DLBCL has a high frequency of p53 overexpression, and CD5 augments the negative effect of p53 overexpression in DLBCL.

Prognostic Significance of in situ Phenotypic Marker Expression in Diffuse Large B-cell Lymphomas

Diffuse large B-cell lymphomas (DLBCL) are the most common lymphoid malignancies, and encompass all malignant lymphomas characterized by large neoplastic cells and B-cell derivation. In the last decade, DLBCL has been subjected to intense clinical, phenotypic and molecular studies, and were found to represent a heterogeneous group of tumors. These studies suggested new disease subtypes and variants with distinct clinical characteristics, morphologies, immunophenotypes, genotypes or gene expression profiles, associated with distinct prognoses or unique sensitivities to particular therapy regimens. Unfortunately, the reliability and reproducibility of the molecular results remains unclear due to contradictory reports in the literature resulting from small sample sizes, referral and selection biases, and variable methodologies and cut-off levels used to determine positivity. Here, we review phenotypic studies on the prognostic significance of protein expression profiles in DLBCL and reconsider our own retrospective data on 301 primary DLBCL cases obtained on a previously validated tissue microarray in light of powerful statistical methods of determining optimal cut-off values of phenotypic factors for prediction of outcome.

Second Malignancies and Richter's Syndrome in Patients with Chronic Lymphocytic Leukemia

Second malignancies are frequent complications in patients with chronic lymphocytic leukemia (CLL). Patients with this leukemia may develop large cell lymphoma (LCL) known as Richter's syndrome (RS). RS occurs in CLL patients of about 3% and may develop in a single lymph node or more often in a group of nodes. However, in some patients extranodal localization of aggressive lymphoma in RS has been observed. Besides LCL, Hodgkin's disease, prolymphocytoid leukemia, multiple myeloma and acute lymphoblastic leukemia may also occur as RS variants. The origin of lymphoid cells in RS remains tentative. However, CLL and RS originate from the same clone for some patients, whereas, in other patients cells of aggressive lymphoma do not have the features of the same clone as the CLL cells. The prognosis of RS is poor. Survival in different studies will be usually 2-5 months. The secondary development or coexistence of myeloproliferative disorders or myelodysplastic syndrome and solid tumors have also been rarely documented in CLL patients. It is of great concern that therapy may further increase the risk of a second neoplasm. However, until now, there are no clear evidence that alkylating agents or purine nucleoside analogs may be associated with an increased incidence of second malignancies in patients with CLL. In this review, epidemiology, biology, clinical characteristic and treatment approaches in RS and other secondary neoplasms in patients with CLL are discussed.

Translocations activating IRF4 identify a subtype of germinal center-derived B-cell lymphoma affecting predominantly children and young adults

The prognosis of germinal center-derived B-cell (GCB) lymphomas, including follicular lymphoma and diffuse large-B-cell lymphoma (DLBCL), strongly depends on age. Children have a more favorable outcome than adults. It is not known whether this is because of differences in host characteristics, treatment protocols, or tumor biology, including the presence of chromosomal alterations. By screening for novel IGH translocation partners in pediatric and adult lymphomas, we identified chromosomal translocations juxtaposing the IRF4 oncogene next to one of the immunoglobulin (IG) loci as a novel recurrent aberration in mature B-cell lymphoma. FISH revealed 20 of 427 lymphomas to carry an IG/IRF4-fusion. Those were predominantly GCB-type DLBCL or follicular lymphoma grade 3, shared strong expression of IRF4/MUM1 and BCL6, and lacked PRDM1/BLIMP1 expression and t(14;18)/BCL2 breaks. BCL6 aberrations were common. The gene expression profile of IG/IRF4-positive lymphomas differed from other subtypes of DLBCL. A classifier for IG/IRF4 positivity containing 27 genes allowed accurate prediction. IG/IRF4 positivity was associated with young age and a favorable outcome. Our results suggest IRF4 translocations to be primary alterations in a molecularly defined subset of GCB-derived lymphomas. The probability for this subtype of lymphoma significantly decreases with age, suggesting that diversity in tumor biology might contribute to the age-dependent differences in prognosis of lymphoma.

The therapeutic effect of rituximab on CD5-positive and CD5-negative diffuse large B-cell lymphoma

The prognosis of diffuse large B-cell lymphoma (DLBCL) has improved markedly in recent years of rituximab era. The prognosis of de novo CD5-positive DLBCL is reported to be poor, but the effect of rituximab on this type of lymphoma remains unclear. To investigate the effect of rituximab on CD5-positive DLBCL, we collected DLBCL patients and analysed prognostic factors. A total of 157 patients with DLBCL who were immunophenotyped with flow-cytometry (FCM) and treated with chemotherapy were subjected to analysis. Those treated with radiotherapy alone or with supportive therapy only were not included. Patients diagnosed in 2003 or later were treated with rituximab combined chemotherapy. There were 95 males and 62 females. Their age ranged from 20 to 91 years old, and the median was 65 years. Nineteen patients were diagnosed as having de novo CD5-positive DLBCL. Rituximab was given alongside chemotherapy in 85 patients. Of these, 11 were positive for CD5 and 74 were negative. The addition of rituximab improved the overall survival (OS) of DLBCL patients (2-year OS: 82% vs. 70%, p = 0.01). For CD5-negative DLBCL, patients treated with rituximab showed 2-year OS of 84%, which was significantly better than those treated without rituximab (70%, p = 0.008). However, for CD5-positive DLBCL, the prognosis was not statistically different between the patients treated with and without rituximab (59% vs. 50%, p = 0.72). Although rituximab improved the prognosis of DLBCL, such improvement was restricted to the CD5-negative group. Further investigation is required to improve the prognosis of patients with CD5-positive DLBCL.

Prognostic evaluation of immunohistochemical profiles in diffuse large B-cell lymphoma: a Chinese study

Diffuse large B-cell lymphoma (DLBCL) has been classified into different prognostic subgroups using immunohistochemistry in Western populations. However, the applicability in Chinese patients of these subgroups was unclear. We collected 116 specimens and performed immunohistochemical staining for CD10, BCL-6, MUM1, CD138, and CD5, and the results were classified into subgroups according to 3 different algorithms. We then analyzed the subgroups' correlation to patient survival. Expression of CD10 and BCL-6 predicted favorable 5-year OS (70 and 62.5%, respectively) and PFS (64.3 and 61.5%, respectively) rates. In contrast, the expression of MUM1 predicted unfavorable 5-year OS (23.1%) and PFS (17.9%) rates and was also independent of other markers. All algorithms led to useful subclassifications. Using Hans' algorithm based on CD10, BCL-6, and MUM1, the non-germinal center (GC) subgroup (66.4%) had worse 5-year OS (29.8%) and PFS (26.7%) rates than did the GC subgroup. Likewise, using Muris' algorithm based on CD10 and MUM1, fewer non-GC cases (27%) showed poorer OS (20.3%) and PFS (16.2%) rates than did GC cases, an effect that was independent of both the International Prognostic Index, a clinical indicator, and treatment. It identified a subgroup with a high-risk of death and seemed to be applicable in our series. In conclusion, these algorithms can be used effectively in Chinese patients with DLBCL.

De novoCD5-positive diffuse large B-cell lymphoma of the skin arising in chronic limb lymphedema

We report the case of a 79-year-old woman with a longstanding lymphedema of the right arm who developed a skin lymphoma involving the right wrist area. Microscopically, the lesion was composed of numerous centroblasts infiltrating both the dermis and the subcutaneous tissue. Phenotypic investigations showed expression of CD20, CD79a, and bcl-2 protein by neoplastic cells. In addition, these cells were CD5 positive. No expression of anaplastic large cell lymphoma kinase (ALK), CD10, CD23, CD30, CD43, bcl-6, cyclin D1, p53 or p16INK4a could be seen. Polymerase chain reaction (PCR) analysis demonstrated a clonal rearrangement of the genes coding for the kappa light chain of the immunoglobulin (Ig). No rearrangement of the genes coding for the Ig heavy chain, t(14;18) or t(11;14) chromosome translocations, or Epstein-Barr virus (EBV) genomic sequences could be found. The tumor was classified as stage IE and was first cured by complete surgical excision. Nineteen months later, a recurrence was noted in the right elbow area. This study further illustrates that lymphoma of the skin may complicate chronic limb lymphedema. Like most of the previously reported cases, this neoplasm belonged to the category of diffuse large B-cell lymphoma. However, it showed CD5 expression as a singular feature.

Diffuse Large B-Cell Lymphoma—More Than a Diffuse Collection of Large B Cells: An Entity in Search of a Meaningful Classification

Context.—Diffuse large B-cell lymphoma is a heterogenous group of lymphomas. In this review, we present a brief description of the large number of entities recognized in the recently published (2008) World Health Organization classification of tumors of hematopoietic and lymphoid tissues.

Objective.—We highlight the unique clinicopathologic and molecular genetic features of these new and previously recognized entities, to illustrate the rational for the development of this classification. To help simplify the understanding of this now large and complex group of diseases, we have attempted to create broader subgroups of related entities. We discuss large B-cell lymphoma that are not otherwise specified, those that are based on anatomic site, those that have unique histology or phenotype or genotype, those that are associated with Epstein-Barr virus or Kaposi sarcoma–associated herpesvirus and herpesvirus 8, and those that are unclassifiable.

Data Sources.—World Health Organization classification of tumors of hematopoietic and lymphoid tissues (2008), published literature from PubMed (National Library of Medicine), and primary material from the authors' institution were reviewed.

Conclusions.—Recognition of the different subtypes of diffuse large B-cell lymphoma as described in the World Health Organization classification scheme will lead to improved understanding of the unique clinicopathologic and genetic features associated with these subtypes of lymphoma.

Prolymphocytoid transformation of follicular lymphoma with coexpression of CD5 and CD10

Histologic transformation of follicular lymphoma is usually to a diffuse large B-cell lymphoma. We present a rare example of a histologic transformation of follicular lymphoma manifested by prolymphocytoid morphology and an unusual immunophenotype characterized by coexpression of CD5 and CD10. The transformed prolymphocytoid lymphoma was positive for CD5 and CD10 antigens by both flow cytometry and immunohistochemistry. The case also expressed bcl-2 and bcl-6 proteins, and exhibited t(14;18), consistent with derivation from a pre-existing follicular lymphoma. Polymerase chain reaction analysis of the immunoglobulin kappa light chain genes derived from the follicular lymphoma and prolymphocytoid lymphoma showed identical rearranged bands, suggesting clonal identity of the two neoplasms. The basis for coexpression of CD5 and CD10 remains unclear. Because the preceding low-grade follicular lymphoma was positive only for CD10 and did not express CD5, CD5 expression appears to be an acquired phenomenon accompanying the process of histologic transformation in this particular case. Prolymphocytoid transformation, similar to other histologic forms of transformation of follicular lymphoma, appears to accompany clinical progression of disease.

IgVH Mutational Status and Clonality Analysis of Richter's Transformation

Approximately 5% of B-cell chronic lymphocytic leukemia (B-CLL) patients develop a secondary aggressive lymphoma, usually of diffuse large B-cell type (DLBCL), termed Richter's transformation (RT). Rarely, classic Hodgkin lymphoma (HL) is observed. Published small series suggest that tumor cells in DLBCL and HL can be clonally identical to the B-CLL clone or arise as an independent, secondary lymphoma. We describe the morphology, immunophenotype, and clinical features of 34 classic RT patients with DLBCL, 6 cases of B-CLL with HL, and 8 cases with scattered CD30-positive Hodgkin and Reed-Sternberg (HRS)-like cells. The clonal relationship of the 2 components was analyzed using sequencing analysis of immunoglobulin heavy chain variable region (IgVH) genes. In classic RT, 18/23 B-CLL cases (78%) showed clonal progression to DLBCL with identical IgVH sequences in both lymphoma components, whereas in 5 cases (22%) the DLBCL was clonally unrelated. Among clonally related RT samples, 73% carried unmutated IgVH genes, whereas 4/5 unrelated cases were mutated. Immunophenotypically, most cases of DLBCL irrespective of clonal relatedness showed significant differences in phenotype compared with the B-CLL, with common loss of CD5 and CD23. Using immuno-laser capture microdissection, sequencing of the IgVH CDR3 region of isolated HRS cells showed that 2/2 cases with HL were clonally unrelated, whereas they were clonally identical in 1/2 cases of B-CLL with scattered HRS-like cells. HRS or HRS-like cells in all 3 unrelated cases showed evidence of Epstein-Barr virus infection. Of interest, 5/6 cases of B-CLL with HL, and 5/6 cases of B-CLL with HRS cells showed mutated IgVH genes.

Expression of ice, bcl-2, c-myc and p53 in different bone marrow cell populations from patients with diffuse large B-cell lymphoma

We have previously reported functional alterations in vitro in the hematopoietic compartment of patients with diffuse large B-cell lymphoma (DLBCL). In the present study, we assessed the presence of molecular alterations in hematopoietic cells derived from DLBCL marrow. Accordingly, the expression of four genes (i.e. ice, bcl-2, c-myc and p53) was assessed both, at the mRNA and protein levels, in three cell populations: (i) population I, consisting of morphologically recognizable precursor and mature cells; (ii) population II, enriched for CD34+ Lineage-negative (Lin-) cells; and (iii) population III, enriched for CD34+ CD38- Lin- cells. By using a multiplex reverse transcriptase-polymerase chain reaction system, we observed reduced expression of bcl-2 in population I, and c-myc in populations I and II from lymphoma marrow compared to their normal counterparts. On the other hand, expression of ice and p53 was not significantly different when comparing normal and DLBCL samples. At the protein level, all four molecules were expressed in a higher proportion of samples from DLBCL patients than in marrow samples from normal subjects. Interestingly, these proteins were expressed predominantly in primitive cells (population III), whereas the proportion of positive samples was reduced in population II, and even more in population I. Taken together, our results indicate that, in DLBCL, molecular alterations are present in hematopoietic cells from bone marrow, including morphologically recognizable precursor and mature cells, as well as primitive hematopoietic progenitors (CD34+ cells). To date, the physiological implications of these alterations are still unclear, and further studies should be undertaken to address this issue.

De novo CD5+ diffuse large B cell lymphoma with basophilia in the peripheral blood: successful treatment with autologous peripheral blood stem cell transplantation

Basophils play an important role in allergic inflammation and are pathologically related to hematological disturbances, such as iron deficiency anemia and myeloproliferative disorders; however, they are only rarely encountered in lymphoid malignancies. Here, we report the case of a 33-year-old man with a bulky mass of the small intestine, multiple paraaortic lymphoadenopathy, pleural effusion, and ascites, who was diagnosed as a case of de novo CD5+ diffuse large B cell lymphoma (DLBCL). This patient showed a marked elevation of the basophil count in the peripheral blood, which appeared to run in parallel with the tumor burden. High dose chemotherapy followed by autologous peripheral blood cell transplantation yielded complete remission, and the patient has remained disease free for 5 years. To the best of our knowledge, this is the first report of a case of de novo CD5+ DLBCL showing marked elevation of the PB basophil count.

Prognostic Biomarkers in Diffuse Large B-Cell Lymphoma

Diffuse large B-cell lymphoma (DLBCL) is the most common type of non-Hodgkin's lymphoma. Although it represents a curable disease, less than half of the patients are cured with conventional chemotherapy. The highly variable outcome reflects a heterogeneous group of tumors, with different genetic abnormalities and response to therapy. The International Prognostic Index (IPI) is useful in predicting the outcome of DLBCL patients. However, patients with identical IPI still exhibit marked variability in survival, suggesting the presence of significant residual heterogeneity within each IPI category. The discovery of specific genetic alterations and the assessment of protein expression led to the identification of multiple novel single molecular markers capable of predicting the outcome of DLBCL patients independently of clinical variables. The recent application of DNA microarrays and tissue array technologies allowed a better understanding of the biology of lymphoma and the development of novel diagnostic tools capable of improving the current models for outcome prediction. However, much confusion exists in the literature regarding the importance of different prognostic biomarkers and their applicability in routine practice. This review summarizes the recent advances in our understanding of prognostic biomarkers in DLBCL and discusses whether this is the right time for biomarkers-guided risk-adjusted therapy.

Biomarkers of potential prognostic significance in diffuse large B-cell lymphoma

Diffuse large B-cell lymphoma (DLBCL) is a biologically heterogeneous disease for which the current approach to treatment is only successful for 50% of patients. The prognostic value of various clinical and biological factors in predicting treatment outcome is discussed in this paper. A review of the English literature was performed including original articles and relevant reviews from MEDLINE that addressed the topics of DLBCL biology and potential prognostic factors. The International Prognostic Index is, to date, the most successful clinical model for predicting outcome. In addition, a rapidly expanding list of molecules has been identified by conventional and newer diagnostic methods that may be of significant prognostic value. Gene expression profiling has led to the discovery of new biological subtypes of DLBCL based on patterns of gene expression, and a host of new genes that may play important roles in this disease. Various derangements in apoptosis, cell-cycle regulation, differentiation, and signal transduction have been noted, while the host environment and immune response also appear to modify clinical outcome. Although to our knowledge, the fundamental abnormalities underlying DLBCL remain elusive, progress is being continuously made to further the understanding of the biological heterogeneity of this disease and the use of various clinical and biological variables to predict treatment outcome. The goal is to be able to identify subgroups of patients at high risk of treatment failure and develop more effective treatment based on specific biological defects that may represent new rational therapeutic targets.

Cytogenetic features of de novo CD5-positive diffuse large B-cell lymphoma: Chromosome aberrations affecting 8p21 and 11q13 constitute major subgroups with different overall survival

De novo CD5-positive diffuse large B-cell lymphoma (CD5(+)DLBCL) is regarded as a different clinicopathological entity from CD5-negative DLBCL (CD5(-)DLBCL) and mantle cell lymphoma (MCL). Because only a few published cytogenetic studies of de novo CD5(+)DLBCL are available, we investigated chromosomal changes in 23 Japanese patients who had de novo CD5(+)DLBCL. A characteristic of cytogenetic abnormalities in de novo CD5(+)DLBCL was a high incidence of chromosomal aberrations affecting 8p21 and 11q13. Major chromosomal breakpoints were concentrated at 8p21, 11q13, and 3q27. Patients with 8p21 aberrations showed aggressive clinical features, including advanced stage of disease, elevated serum LDH level, poor performance status, and an inferior survival curve compared with patients who had 11q13 changes (P = .043). Chromosomal abnormalities of both 8p21 and 11q13 were not observed in the same patient, and each abnormality showed different chromosomal gains and losses. These results indicate that de novo CD5(+)DLBCL may occur in previously unidentified subgroups that differ in their chromosomal abnormalities. The conflicting results of previous studies on prognosis may thus be explained in part by the differences in chromosomal changes.

Emerging prognostic factors in diffuse large B cell lymphoma

PURPOSE OF REVIEW

Diffuse large B cell lymphoma (DLBCL) is the most common lymphoma subtype, characterized by marked clinical and biologic heterogeneity. Gene expression studies together with new monoclonal antibody production are playing an increasing role in determining important prognostic factors/biomarkers predictive of outcome. Despite these technical advances, much confusion exists in the literature as to what constitutes the important biomarkers for determining patient outcome. The purpose of this review is to highlight recent advances in our understanding of novel biomarkers in DLBCL and how these might be incorporated into current risk-adjustment models for prognosis.

RECENT FINDINGS

Microarray gene expression analyses have revolutionized our approach to biomarkers in non-Hodgkin lymphomas. Thousands of genes can now be simultaneously analyzed for individual patients, creating a wealth of new data. This has resulted in an improved understanding of the basic biology, as well as the development of new outcome predictors. Monoclonal antibody reagents for some of these biomarkers already exist, allowing for their rapid validation at the level of protein expression and potential clinical translation.

SUMMARY

A molecular classification of DLBCL is a current reality, and together with routine morphology, immunophenotype, and molecular cytogenetics, has allowed us to more accurately subclassify DLBCL and determine clinically relevant subgroups. The time is right to begin to consider how these novel biomarkers should be incorporated into current prognostic models to move beyond the clinically based International Prognostic Index

De novo CD5 positive diffuse large B-cell lymphomas with bone marrow involvement in Korean

In CD5 positive (CD5+) mature B-cell lymphomas, newly recognized CD5+ diffuse large B-cell lymphoma (DLBCL) has been characterized by aggressive features. We studied twenty-five cases with CD5+ lymphomas involving bone marrow. Eleven cases were diagnosed as chronic lymphocytic leukemia, six cases were diagnosed as mantle cell lymphoma (MCL), and three cases with morphologic characteristics of MCL and without both the cyclin D1 expression and IGH/CCND1 rearrangement were unclassifiable. The remaining five cases, showing large to medium-sized lymphoid cells with prominent nucleoli and a moderate amount of cytoplasm, were diagnosed as DLBCL. Five DLBCL cases were positive for CD5, CD20, surface immunoglobulin, but negative for CD23. Patients with CD5+ DLBCL showed a high age of onset (median, 68 yr) and two patients expired one month after the diagnosis. Since CD5+ DLBCL forms a distinct subgroup of DLBCL, a study of CD5 expression in DLBCL would be helpful to predict prognosis and to determine future therapeutic strategy. To the best of our knowledge, this is the first report on de novo CD5+ DLBCL in Koreans.

Histogenesis of CD5-positive and CD5-negative B-cell neoplasms on the aspect of somatic mutation of immunoglobulin heavy chain gene variable region

The immunoglobulin heavy chain (IgH) gene of B-cells dramatically alters twice in their differentiation to memory or plasma cells; VDJ recombination at B-cell precursor and somatic hypermutation, class switch recombination and receptor revision at germinal center (GC) B-cells. Among them, somatic hypermutation of the IgH gene variable region (VH gene) is a powerful tool for detection of B cell differentiation. B-cells and B-cell neoplasms have been divided into following; 1) pre-GC B-cells and neoplasms with a germline VH gene and 2) GC and post-GC B-cells and neoplasms with a somatically mutated VH gene. In this article, we review normal B-cell differentiation and histogenesis of various types of B-cell neoplasms on the aspect of somatic mutation of the rearranged VH gene. In particular, differences between CD5+ and CD5- B-cell neoplasms, using our own data of over 100 cases with B-cell neoplasms, are discussed. Although CD5+ B-cells are included in pre-GC B-cells for the reason of germline VH gene in most of CD5+ B-cells, an about 5% of CD5+ B-cells show somatically mutated VH gene. The rearranged VH gene of CD5+ B-cell neoplasms shows heterogeneity, whereas CD5- B-cell neoplasms possess somatically mutated VH gene with a mean of 8 approximately 12%. Both CD5+ B-cell chronic lymphocytic leukemia and CD5+ diffuse large B-cell lymphoma display that about half of cases show a germline or low frequency of somatic mutation and the others possess somatically mutated VH gene. CD5+ mantle cell lymphoma constitutes most cases with germline and a small number of cases with mutated VH gene. Therefore, CD5- B-cells & CD5- B-cell neoplasms are distinct from CD5+ B-cells and CD5+ B-cell neoplasms in somatic mutation of VH gene. It suggests that each of CD5- and CD5+ B-cells independently has its own differentiation.

Relationship between the mutational status of VH genes and pathogenesis of diffuse large B-cell lymphoma in Richter's syndrome

Patients with chronic lymphocytic leukemia (CLL) may develop diffuse large B-cell lymphoma (DLBL), also known as Richter's syndrome. Mutational status of immunoglobulin (Ig) heavy-chain variable region (VH) genes have prognostic impact in CLL. Patients with mutated VH genes have a stable disease, whereas patients with unmutated VH gene have more aggressive disease. The mutational status of CLLs that transform to DLBL is unknown. To reveal whether Richter's syndrome occurs in CLLs with mutated or unmutated VH genes, we have performed mutational analysis on serial specimens from eight patients. CLL and DLBL tumorclones were identical in five cases and they were different in three cases. Six CLLs expressed unmutated and two cases expressed mutated VH genes. In five of the six unmutated CLLs, the DLBL clones evolved from CLL tumorclones and the VH genes expressed by DLBLs were also unmutated. In one unmutated and two mutated CLLs, the DLBLs expressed mutated VH genes, but in these three cases the DLBL tumorclones developed as independent secondary neoplasm. These results suggest that Richter's syndrome may develop in both mutated or unmutated CLLs, but clonal transformation of CLL to DLBL occur only in the unmutated subgroup of CLL.

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.