Single clonal origin of neoplastic B-cells with different immunoglobulin light chains in a patient with Richter's syndrome

SOHO State of the Art Updates and Next Questions | Treatment of Richter's Transformation

Richter's transformation (RT) is a rare condition, represented by the development of an aggressive lymphoma arising from underlying chronic lymphocytic leukemia/small lymphocytic lymphoma. The management of RT remains challenging, necessitating combined therapeutic strategies to achieve favorable outcomes. Traditional treatment options for RT have involved intensive chemotherapy regimens, often with limited success due to the high-risk nature of the disease. However, recent advances in the understanding of RT pathogenesis have led to the emergence of novel targeted therapies that show promising results. Noncovalent Bruton tyrosine kinase inhibitors, T-cell-engaging bispecific antibodies, chimeric antigen receptor T-cells, and conjugated monoclonal antibodies may hold promise for improved outcomes in RT, especially when combined in a multitargeted fashion. Further prospective randomized trials and collaborative efforts are warranted to optimize treatment algorithm and ultimately improve patient outcomes in this dismal condition. This review provides a comprehensive overview of the current treatment options for RT.

Treatment of Richter Transformation of Chronic Lymphocytic Leukemia in the Modern Era

Richter Transformation (RT) refers to the development of an aggressive lymphoma in the setting of chronic lymphocytic leukemia (CLL). While many variants of RT are recognized, diffuse large B-cell lymphoma (RT-DLBCL) is the most common (80%), followed by Hodgkin’s lymphoma (RT-HL, 19%). Diagnosis is based upon histologic evaluation of clinically suspicious lymph nodes. Positron emission tomography (PET) may be used to select the node of interest for biopsy. Although clonality testing is not a prerequisite of RT diagnosis, it has significant implications for survival. Clonally related DLBCL carries the worst prognosis with a median overall survival (OS) of less than one year in the era of combination chemotherapies with or without anti-CD20 antibodies. Prognosis has improved with the use of stem cell transplant and newer agents such as targeted therapy and newer forms of immunotherapy. Consideration of a clinical trial is encouraged. This review describes our current understanding of RT and focuses on treatment of RT-DLBCL, including clinical trials in progress and new therapies in development. We also report an illustrative example of a patient with clonally related DLBCL who survived two years after diagnosis without the use of combination chemotherapy.

Treatment of Richter's syndrome

Richter's syndrome (RS) is an aggressive histologic transformation of chronic lymphocytic leukemia (CLL), most commonly to diffuse large B-cell lymphoma (DLBCL). Outcomes are generally poor, with complete remission (CR) rates of only about 20% and less than 20% long-term survival with chemoimmunotherapy (CIT). RS is biologically heterogeneous, and in 80% of patients with CLL who develop DLBCL, the disease is clonally related to the CLL. Clonally unrelated cases are genetically and immunologically distinct from clonally related DLBCL-RS, have more favorable responses to CIT, and are best treated as de novo DLBCL. Relatively favorable outcomes with CIT are also seen in patients who have never previously received treatment for CLL and who lack TP53 mutation or deletion. For the remaining patients, treatment on a clinical trial is optimal. Fortunately, numerous agents are now in clinical development that show encouraging results. Here we review clinical data for some of the most promising approaches. DLBCL-RS tumor cells frequently express programmed cell death 1 protein (PD-1), and several studies have demonstrated activity for PD-1 inhibitors, especially in combination with ibrutinib. The BCL2 inhibitor venetoclax in combination with R-EPOCH CIT achieved CR in 50% of patients, and a study of venetoclax-R-CHOP is ongoing. The noncovalent Bruton's tyrosine kinase inhibitor pirtobrutinib has achieved responses in approximately two-thirds of heavily pretreated patients and, given its favorable toxicity profile, appears ideally suited to combining with other active agents. Finally, we review available data for bispecific antibodies, antibody-drug conjugates, and chimeric antigen receptor T-cell therapy, which, after revolutionizing the treatment of DLBCL, are now being evaluated in RS.

Transformation to diffuse large B-cell lymphoma with germinal center B-cell like subtype and discordant light chain expression in a patient with Waldenström macroglobulinemia/lymphoplasmacytic lymphoma

Waldenström macroglobulinemia (WM)/lymphoplasmacytic lymphoma (LPL) is a rare indolent B-cell neoplasm, and a gain-of-function mutation in the myeloid differentiation primary response 88 (MYD88), L265P, is a commonly recurring mutation in patients with WM/LPL. Histological transformation of WM/LPL to an aggressive lymphoma such as diffuse large B-cell lymphoma (DLBCL) is rare, and transformed DLBCL has a worse prognosis than de novo DLBCL, partly because transformed DLBCL is mostly classified as non-germinal center B-cell-like (non-GCB) subtype. We herein describe a 75-year-old man with DLBCL with a history of WM/LPL. DLBCL in this patient showed the GCB subtype, and the light chain restriction of DLBCL was different from that of the antecedent WM/LPL, indicating that the two types of lymphoma cells had distinctive origins. However, DLBCL in this patient harbored the MYD88 L265P mutation, and polymerase chain reaction and Sanger sequencing of the DLBCL and WM/LPL for immunoglobulin heavy chain gene rearrangement suggested a clonal relationship between the two lymphomas. Since the outcome of transformed DLBCL is worse than for de novo DLBCL, it is important to evaluate the clonal relationship between primary WM/LPL and the corresponding transformed DLBCL, even if the DLBCL expresses a GCB subtype or discordant light chain restriction.

Simultaneous Presentation of Lymphomatoid Granulomatosis and Multiple myeloma in an Immunodeficient Patient with Rheumatoid Arthritis

A 75-year-old Japanese woman with a 20-year history of rheumatoid arthritis presented with symptomatic bilateral pleural effusion and lung and brain tumors. She had received methotrexate for five years and tacrolimus for one year. A brain biopsy specimen showed the pathological features of lymphoproliferative disease, but a bone marrow biopsy showed proliferation of plasma cells. She was finally diagnosed with coexistent lymphomatoid granulomatosis (LYG) of the brain and lung and multiple myeloma (MM) of the bone marrow and received chemotherapy for both. This report shows that immunodeficient patients are at risk of developing the unusual coexistence of LYG and MM.

Pathology of chronic lymphocytic leukemia: an update

Chronic lymphocytic leukemia (CLL)/small lymphocytic lymphoma (SLL) is a clonal lymphoproliferative disorder characterized by proliferation of morphologically and immunophenotypically mature lymphocytes. CLL/SLL may proceed through different phases: an early phase in which tumor cells are predominantly small in size, with a low proliferation rate and prolonged cell survival, and a transformation phase with the frequent occurrence of extramedullary proliferation and an increase in large, immature cells. Although some patients with CLL have an indolent disease course and die after many years of unrelated causes, others have very rapidly disease progression and die of the disease within a few years of the diagnosis. In the past few years, considerable progress has been made in our ability to diagnose and classify CLL accurately. Through cytogenetics and molecular biology, it has been shown that CLL and variants are associated with a unique genotypic profile and that these genetic lesions often have a direct bearing on the pathogenesis and prognosis of the disease. Similarly, the development of antibodies to new biologic markers has allowed the identification of a unique immunophenotypic profile for CLL and variants. Moreover, accumulating evidence suggests that CLL cells respond to selected microenvironmental signals and that this confers a growth advantage and an extended survival to CLL cells. In this article, we will review the progress in the pathobiology of CLL and give an update on prognostic markers and tools in current pathology practice for risk stratification of CLL.

Biclonal low grade B-cell lymphoma confirmed by both flow cytometry and karyotypic analysis, in spite of a normal kappa/lambda Ig light chain ratio

Composite low grade lymphoma with two subpopulations in a same site is uncommon. We herewith report the case of an 80-year-old woman who presented with isolated bilateral dacryoadenomegaly. Pathological examination of an incisional biopsy of her right lacrimal gland was consistent with a marginal zone lymphoma. Flow cytometry immunophenotyping showed two distinct clonal B-cell populations expressing sIg D lambda or sIg M kappa restriction in the lacrimal gland, blood, and bone marrow. Both B-cells populations were sorted from peripheral blood for molecular biology investigations and comparison with molecular data performed on tumor and bone marrow cells. IgH PCR performed on purified blood populations disclosed two monoclonal peaks: 98 bp-sized peak in the sIg M kappa and a 107 bp in the sIg D lambda clones, respectively. The lacrimal gland tumor expressed mainly sIg M kappa population, and showed a major 98 bp-sized peak coexisting with a very minor 107 bp peak. Cytogenetic studies showed a 46, XX,del (7) (q22q32) karyotype. Bone marrow examination at diagnosis revealed the same B-cell clones distribution than the one observed in blood with a dominant sIg D lambda population, a Genescan profile showing a major peak of 107 bp and a minor peak of 98 bp. Chromosomal analysis disclosed a 46,XX,del (10) (?p14) karyotype without detectable 7q deletion. To our knowledge, this observation represents the first reported case of biclonal low grade lymphoma hidden behind a normal classical kappa/lambda Ig light chain ratio in blood, but clearly demonstrated by the combination of three ancillary techniques (flow cytometry both analytical and cell sorting, molecular biology, and cytogenetics) and analysis of different tissues (i.e., in this case, lacrimal gland biopsy, blood, and bone marrow).

Recent advances in the diagnosis and therapy of richter’s syndrome

Richter's syndrome (RS) denotes the development of aggressive lymphoma that arises in patients with chronic lymphocytic leukemia (CLL). Presenting features typically include a rapid clinical deterioration with fever in the absence of infection, progressive lymph node enlargement, and an elevation in serum LDH. Diagnostic biopsy of affected sites usually reveals large cell lymphomas; however, Hodgkin variant cases have been described. Richter's transformation occurs in approx 5% of CLL patients and may be associated with infection with Epstein-Barr virus (EBV). Chromosome 11 and 14 abnormalities have also been described as well as tumor suppressor gene defects involving p53, p21, and p27. Treatment options for these patients are limited and include combination chemotherapy with or without the addition of monoclonal antibodies and stem cell transplantation. Response to therapy is variable and generally short-lived. Median survival is usually in the order of 5-8 mo. More effective management for RS is needed as well as prognostic models that will identify CLL patients at risk of transformation. This review will address the current status of RS and deal with the pathophysiology, diagnostic approach, and treatment of this challenging disease.

Richter syndrome: biology, incidence, and therapeutic strategies

Richter's transformation denotes the development of high-grade non-Hodgkin lymphoma, prolymphocytic leukemia, Hodgkin disease, or acute leukemia in patients with chronic lymphocytic leukemia (CLL)/small lymphocytic lymphoma. A search of published articles in Medline (PubMed) and abstracts from professional meetings was performed. An electronic database search of patients with CLL at The University of Texas M. D. Anderson Cancer Center (Houston, TX) determined the incidence of Richter syndrome (RS) in patients with CLL between 1992 and 2002. RS occurs in approximately 5% of patients with CLL. The large cells of RS may arise through transformation of the original CLL clone or represent a new neoplasm. RS may be triggered by viral infections, such as Epstein-Barr virus. Trisomy 12 and chromosome 11 abnormalities are more frequent in patients with RS than in the overall population of patients with CLL. Multiple genetic defects, such as mutations of the p53 tumor suppressor gene, p16INK4A, and p21, loss of p27 expression, deletion of retinoblastoma, increased copy number of C-MYC, and decreased expression of the A-MYB gene, have been described. These abnormalities may cause CLL cells to proliferate and-by facilitating the acquisition of new genetic abnormalities-to transform into RS cells. Therapeutic strategies include intensive chemotherapy, monoclonal antibodies, and stem cell transplantation. The response rates range from 5% to 43% (complete response, 5-38%), and the median survival duration ranges from 5 months to 8 months. In conclusion, RS may be triggered by viral infections or by genetic defects. Current treatments are aggressive, but prognosis is poor. Novel curative treatment strategies are needed.

A Common Clonal Origin of Nodal Marginal Zone B-Cell Lymphoma and Plasma Cell Myeloma Demonstrating Different Immunophenotypes

We demonstrated an 83-year-old male case of composite lymphoma. Before 18 years, he was diagnosed with nodal marginal zone B-cell lymphoma in the cervical lymph node. Peripheral blood showed anemia and IgA (kappa)-type monoclonal gammopathy (IgA; 3,625 mg/dL). Bone marrow aspiration biopsy exhibited plasma cell myeloma, in which atypical plasma cells were positive for cytoplasmic IgA (kappa) and atypical lymphoid cells intermingled were positive for CD20. In contrast, cervical lymph node biopsy revealed nodal marginal zone B-cell lymphoma, in which lymphoma cells were positive for cytoplasmic IgG (lambda). Southern blotting analysis of the IgH gene showed same clonal rearrangement band in both lymph node and bone marrow samples and additional band in the bone marrow. Sequence analyses of the IgH gene showed an identical sequence of CDR3 in both samples. Thus, we demonstrated a common clonal origin of composite lymphoma comprising nodal marginal zone B-cell lymphoma and plasma cell myeloma. Nodal marginal zone B-cell lymphoma recurred in cervical lymph node and involved into the bone marrow, differentiating into plasma cell myeloma in which Ig isotype switched and monoclonal gammopathy developed. Sequence analysis of the IgH gene was a powerful tool for determination of clonal origin.

Composite lymphoma: angiocentric T-cell lymphoma (CD8+ cytotoxic/supressor T-cell) and diffuse large B-cell lymphoma associated with EBV, and presenting clinically as a midfacial necrotizing lesion

A composite lymphoma is defined as the simultaneous occurrence of two histologically different types of lymphomas situated in one anatomical location. Reports of composite B- and T-cell lymphomas, especially in the head and neck region, are rare. We describe a 76-year-old Taiwanese aboriginal female patient clinically presenting with a midfacial necrotizing lesion (MNL). Microscopic examination of the incisional biopsy specimen revealed extensive surface necrosis with infiltrates of inflammatory cells. Beneath the necrotic surface, there appeared to be two distinct populations of pleomorphic lymphoid cells exhibiting the characteristic features of the angiocentric distribution of the tumor cells and evidence of angiodestruction. Immunohistochemical staining revealed that these atypical lymphoid cells were positive for LCA, CD45, CD5, CD20, CD3 epsilon, CD8, bcl-2 and bcl-6 and negative for CD56, CD4, CD68, keratin, S-100, kappa and lambda. Furthermore, these atypical lymphoid cells also expressed EBV-encoded nuclear RNAs (EBERs) following in situ hybridization. Therefore, this was a case of composite lymphoma: angiocentric T-cell lymphoma (ATCL) (CD8+ cytotoxic/suppressor T-cell) and diffuse large B-cell lymphoma (DLBL) associated with the Epstein-Barr virus (EBV) and presenting clinically as MNL.

Simultaneous manifestation of chronic lymphocytic leukemia (CLL) and hairy cell leukemia (HCL)

We report a unique case of 83-year-old Caucasian male with the initial simultaneous manifestation of chronic lymphocytic leukemia (CLL) and hairy cell leukemia (HCL). The patient presented with absolute lymphocytosis in the blood, asymptomatic generalized lymphadenopathy, and mild splenomegaly. The diagnosis of CLL was suggested from the blood film, but subsequent flow cytometric (FC) analysis on peripheral blood mononuclear cells (PBMNC) revealed two distinct abnormal clones of mature B cells. A small subpopulation (7%) of lymphoid cells expressed CD20, CD11c, FMC-7, CD103, CD25, and kappa surface light chain, consistent with HCL. The larger subpopulation (75%) of lymphoid cells expressed CD19, CD20, CD23, CD5, and lambda light chain, consistent with CLL. The expression of different immunoglobulin light chains on the circulating CLL (lambda) and HCL (kappa) cells suggested two, independent, malignant B-cell clones. Interestingly, FC analysis of bone marrow (BM) cells done 6 months later revealed bright lambda light chain expression on the HCL cells. Despite administration of several different courses of chemotherapy, the HCL subpopulation was not eliminated from the BM but remained stable between 7% and 10% of total BM lymphoid cells. The CLL, responsible for most of clinical symptoms in our patient, responded to combination chemotherapy with fludarabine and cytoxan, and later to monotherapy with rituximab.

The clinical significance of large cells in bone marrow in patients with chronic lymphocytic leukemia

BACKGROUND

Patients with chronic lymphocytic leukemia (CLL) that transforms to Richter syndrome (RS) frequently show atypical lymphocytes in bone marrow; however, a diagnosis of RS requires confirmation of the presence of sheets of large cells in bone marrow or lymph nodes.

METHODS

In this study, the authors evaluated the clinical significance of scattered large cells in bone marrow. They assessed the possibility of predicting transformation to RS in bone marrow smears by counting the percentages of prolymphocytes and large cells in 78 patients with CLL and 29 patients with lymph node biopsy-confirmed RS.

RESULTS

The percentage of large cells was found to be correlated with decreasing survival in a continuous fashion (P = 0.006). It is interesting to note that patients who had > 7% large cells in the bone marrow and elevated beta(2)-microglobulin (beta(2)-M) levels (> 5 mg/L) had a survival duration identical to that of patients with RS, and these factors together were a strong predictor of RS (P < 0.001).

CONCLUSIONS

Patients with CLL who had bone marrow that contained > 7% large cells and who had beta(2)-M levels > 5 mg/L had a disease that was similar to RS, and the combination of large cells and beta(2)-M can be used as a surrogate marker for RS.

Richter syndrome in B-cell chronic lymphocytic leukemia

Richter syndrome (RS) is well known as a secondary high-grade lymphoma, mostly diffuse large B-cell lymphoma (DLBCL) developed in patients with B-cell chronic lymphocytic leukemia (B-CLL). In this review, we describe clinicopathological, histological, immunophenotypical and genetic findings of RS. The patients with RS, regardless of transformation of pre-existing clone or de novo malignant clone, were resistant to conventional combined chemotherapy and died within months of diagnosis. Molecular techniques can provide convincing results for the clonal relationship of RS to pre-existing B-CLL. When RS carries a same rearrangement band or a same sequence as B-CLL by Southern blotting or nucleotide sequence analyses of immunoglobulin heavy and/or light chain genes, it is suggested to that RS transforms from original B-CLL. These analyses have showed that approximately two-thirds of RS cases evolved from a B-CLL clone. How and where does the B-CLL clone evolve to RS? The genetic alteration of transforming B-CLL clone into RS has been addressed. Abnormalities of chromosomes 11 and 14 were most frequently involved in RS, but non-specific. In addition, RS does not include chromosomal translocation between Ig locus and oncogenes or rearrangements of bcl-6 gene, both of which were found in some de novo DLBCL. Several candidates, such as mutation of p53 gene and abnormalities of cyclin dependent kinase inhibitor, have been proposed to play an important role in the transformation of a part of B-CLL. However, there is still uncertainty as to how B-CLL progresses or develops into RS.

Frequent discordance of the light-chain isotypes expressed by serum monoclonal components and leukaemic B-cells

In B-cell malignancies, it is generally held that the monoclonal components (MC) are produced by the malignant clones. Genetic relatedness implies the concordant expression of light-chain (LC) isotypes in the MC and at the surface of the malignant lymphocytes. We reviewed a series of 91 B-cell leukaemias, immunophenotyped by flow cytometry in our laboratory. A serum MC had been sought in 75 of these patients, and had been found in 23 (31%). Biclonal serum components were detected in three cases. LC concordance could not be assessed in three cases of surface LC-null lymphocytes. Of the 23 MC studied in 20 patients, light-chains were discordant in 39%, mostly due to kappa MC in lambda leukaemias. The origin of LC discordance remains speculative. It could be due to the emergence of subclones with the same primal VDJ gene rearrangement or, alternatively, to the development of new B-cell clones escaping immune surveillance from deregulated T-cells.

Primary Digestive Richter's Syndrome

The clinical and morphologic transformation of 3 to 5% of chronic lymphocytic leukemia (CLL) to diffuse large-cell lymphoma (DLCL) is commonly referred to as Richter's syndrome. Richter's syndrome occurs mostly in lymph nodes and may represent a second neoplasm or a transformation from the same clonal population. Clinical features in six patients with digestive Richter's syndrome were recorded. Paired samples of CLL and DLCL were investigated by immunohistological analysis (n = 6) and by polymerase chain reaction (PCR) for immunoglobulin heavy-chain gene rearrangement (n = 4). Histological examination revealed the involvement of the gastrointestinal tract by DLCL of B-cell phenotype (n = 6). The same monoclonal rearrangement between CLL and DLCL was demonstrated by PCR and sequencing analyses in two patients. The monoclonal rearrangement was different between CLL and DLCL in only one case. Median survival was 22 months for five patients receiving chemotherapy, suggesting that digestive Richter's syndrome has a better prognosis than nodal Richter's syndrome. Indeed, appropriate surgical resection combined with chemotherapy led to partial or complete remission in four patients.

Large cell lymphoma transformation of chronic lymphocytic leukemia/small lymphocytic lymphoma. A flow cytometric analysis of seven cases

We studied 7 cases of large cell transformation of chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) immunophenotyped by multiparameter flow cytometry. The 6 women and 1 man ranged in age from 45 to 91 years. All had previous or concurrent evidence of CLL/SLL. Morphologic features and sites of involvement of the diffuse large B-cell lymphoma (DLBCL) were heterogeneous; 2 cases had paraimmunoblastic morphologic features. Six DLBCLs had an immunophenotype consistent with CLL: CD19+, CD5+, CD23+, and FMC7 negative (3 cases) or very dim (2 cases); 1 case was not studied for FMC7. CD20 was dim in 3 of these, moderate to bright in 2, and variable in 1. Surface immunoglobulin was dim in 2 cases and moderate or bright in 4. Five of 6 expressed CD38. Comparison with the immunophenotypes of the previous or coexistent CLL/SLL (4 of 6 cases) revealed minor modulations in antigen expression but no major alterations. The seventh DLBCL lacked CD5 expression, but otherwise had immunophenotypic features similar to CLL. These findings indicate that DLBCL arising in CLL/SLL tends to retain a CLL immunophenotype, in contrast with de novo CD5+ large cell lymphomas that uncommonly express such a phenotype.

Achieving Optimal Outcomes in Chronic Lymphocytic Leukaemia

Chronic lymphocytic leukaemia (CLL) is a disease of late middle age and older. The majority of patients are diagnosed because of a lymphocytosis of at least 5 x 10(9)/L on an incidental blood count. It needs to be distinguished from mantle cell lymphoma and splenic marginal zone lymphoma by lymphocyte markers. The immunophenotype of CLL is sparse surface immunoglobulin, CD5+, CD19+, CD23+, CD79b-, and FMC7-. The disease is staged according to the presence of lymphadenopathy and/or splenomegaly and the features of bone marrow suppression. Most patients have an early stage of disease when diagnosed and perhaps 50% will never progress. This group of patients have a normal life expectancy and do not require treatment beyond reassurance. Progression involves an increasing white cell count, enlarging lymph nodes and spleen, anaemia and thrombocytopenia. Complications of progression include autoimmune haemolytic anaemia and thrombocytopenia, immunodeficiency, and the development of a more aggressive lymphoma. A range of prognostic factors is available to predict progression, but most haematologists rely on close observation of the patient. Intermittent chlorambucil remains the first choice treatment for the majority of patients. Combination chemotherapy offers no advantage. Intravenous fludarabine is probably more effective than chlorambucil, but no trial has yet shown a survival advantage for using it first rather than as a salvage treatment in patients not responding to chlorambucil. It is at least 40 times as expensive as chlorambucil. Cladribine may be as effective as fludarabine, although it has been used less and is even more expensive. Patients who relapse after chlorambucil should be offered retreatment with the same agent and if refractory should be switched to fludarabine, which may also be offered for retreatment on relapse. For patients refractory to both drugs, a variety of options are available. High dose corticosteroids, high dose chlorambucil, CHOP (cyclophosphamide, prednisolone, vincristine and doxorubicin), anti-CD52, anti-CD20 and a range of experimental drugs which are being evaluated in clinical trials. Younger patients should be offered the chance of treatment with curative intent, preferably in the context of a clinical trial. Autologous stem cell transplantation after achieving a remission with fludarabine has relative safety and may produce molecular complete remissions. Only time will tell whether some of these patients are cured but it seems unlikely. Standard allogeneic bone marrow transplant is probably too hazardous for most patients, but non-myeloablative regimens hold out the hope of invoking a graft-versus-leukaemia effect without a high tumour-related mortality. Trials of immunotherapy are exciting options for a few patients in specialised centres.

De novo CD5+ diffuse large B-cell lymphomas. A heterogeneous group containing an unusual form of splenic lymphoma

We reviewed our institutional experience with de novo CD5+, large B-cell lymphomas to determine whether they represent a distinct entity and are related to CD5+ small B-cell disorders. We identified 13 cases with multiparameter flow cytometry over a period of 58 months (5% of large B-cell lymphomas) in 7 females and 6 males. Three groups were identified. Group 1 (2 cases) had diffuse splenic red pulp involvement with a distinctive cordal pattern of infiltration, no other clinical evidence of mass disease, microscopic disseminated disease on further workup, and an identical immunoglobulin-negative immunophenotype. Group 2 cases (7 cases) were clinically and morphologically heterogeneous and had an immunophenotype resembling mantle cell lymphoma (FMC7-positive, CD23-). Group 3 (4 cases) had miscellaneous immunophenotypes, including one closely resembling chronic lymphocytic leukemia. Cyclin D1 was positive in only 1 of 10 evaluable cases (group 2). We conclude that CD5+ diffuse large B-cell lymphomas are heterogeneous; most cases do not seem to be related to chronic lymphocytic leukemia or mantle cell lymphoma. However, we identified a subgroup of primary splenic CD5+ large B-cell lymphoma with diffuse red pulp involvement and believe this may represent a distinct clinicopathologic entity.

Follicular lymphoma with monocytoid B-cell proliferation: molecular assessment of the clonal relationship between the follicular and monocytoid B-cell components

Although a number of studies have recognized that follicular lymphomas may be accompanied by a prominent proliferation of monocytoid B-cells, the clonal relationship between these components has not been adequately assessed. Using laser capture microdissection, we isolated the follicular and monocytoid B-cell components from four well-characterized cases of follicular lymphoma with prominent monocytoid B-cells. DNA from each component was analyzed using polymerase chain reaction (PCR)-based methods to assess for clonal rearrangements of the immunoglobulin heavy chain gene (IgH) and for the presence of the bcl-2 gene major breakpoint region/joining region (MBR/JH) DNA fusion products by conventional PCR and fluorescence melting curve analysis. Evidence of clonal identity was established in the follicular and monocytoid B-cell components of three cases by demonstration of IgH gene rearrangements of identical size using IgH PCR, by comparison of complementarity determining region III (CDRIII) DNA sequences, or by detection of bcl-2 MBR/JH fusion products of identical size and/or melting temperature. Molecular analysis of the fourth case revealed a monoclonal and MBR/JH-positive follicular component accompanied by a polyclonal and MBR/JH-negative monocytoid B-cell proliferation. We conclude that the follicular and monocytoid B-cell components of this variant of follicular lymphoma are clonally identical in the majority of cases. However, in a minority of these cases, the monocytoid B-cell component is reactive. Larger studies that assess the prognostic significance of follicular lymphoma with monocytoid B-cells will benefit from molecular studies that assess the clonal relationship of both components.

Mycosis fungoides and chronic lymphocytic leukaemia--composite T-cell and B-cell lymphomas presenting in the skin

Composite lymphomas involving cutaneous B-cell and T-cell lymphomas are very uncommon. We report here the unique circumstance of a patient with mycosis fungoides (primary cutaneous T-cell lymphoma) who later developed chronic lymphocytic leukaemia (B-cell lymphoproliferation, B-CLL), which presented in the skin (leukaemia cutis) as a composite lymphoma affecting an earlobe. The presence of both lymphoproliferative disorders was confirmed with immunophenotyping and the finding of both immunoglobulin gene rearrangements and T-cell receptor gene rearrangements in the ear and the same T-cell receptor gene rearrangement in a plaque lesion of mycosis fungoides on the arm.

High-grade transformation of low-grade non-Hodgkin's lymphomas: mechanisms of tumor progression

In the natural history of low-grade non-Hodgkin's lymphomas (NHL) a prolonged indolent phase of the disease may be followed by clinical progression toward intermediate and high-grade disease. The abrupt appearance of diffuse large cell lymphoma (DLL) in patients with low-grade NHL is usually associated with an accelerated clinical course and shorter time of survival. The histologic transformation has been described for chronic lymphocytic leukemia or small lymphocytic lymphoma (CLL/SLL), follicular lymphoma (FL), mantle cell lymphoma (MCL) and lymphoma of mucosa-associated lymphoid tissue (MALT). Although the histological transformation of low-grade lymphomas are relatively frequent, the clonal relationship between the two neoplasms and pathogenetic mechanisms underlying the progression of the disease are widely debated. In this review, we will focus on the possible relationship between the low-grade and the transformed high-grade NHLs and genetic lesions that may be associated with the histologic transformation and clinical progression of the disease.

Composite low grade B-cell lymphomas with two immunophenotypically distinct cell populations are true biclonal lymphomas. A molecular analysis using laser capture microdissection

Low grade B-cell lymphomas comprise several well defined, clinically and immunophenotypically distinct disease entities. Composite lymphomas showing phenotypic characteristics of more than one of these tumor subtypes in the same site are rare, and both common and separate clonal origins of the two tumor parts have been reported for cases studied by molecular methods. We describe the detailed immunohistochemical and molecular findings in three cases with features of composite low grade B-cell non-Hodgkin's lymphoma (B-NHL). All three neoplasms contained morphologically distinct but interwoven compartments of different cell types, which exhibited discordant expression of several markers, including CD5, CD10, CD43, and cyclin D1. According to their morphology and phenotypes, they were classified as mantle cell lymphoma and follicular lymphoma (Case 1), follicular lymphoma and small lymphocytic lymphoma (Case 2), and mantle cell lymphoma and chronic lymphocytic leukemia/small lymphocytic lymphoma (Case 3). PCR analysis of DNA obtained from whole tissue sections failed to reveal evidence for biclonality in any of the cases. We therefore isolated cell populations with different antigen expression patterns by laser capture microdissection and analyzed them by polymerase chain reaction amplification and sequencing of clonal immunoglobulin heavy chain gene rearrangements and oncogene rearrangements. Sequence analysis revealed unrelated clonal rearrangements in each of the two tumor parts in all three cases, suggesting distinct clonal origins. In addition, Case 1 showed a bcl-2 rearrangement present only in the follicular lymphoma part. Our findings suggest that low grade B-NHL with two distinct morphological and immunophenotypic patterns in the same anatomical site are frequently biclonal. This is in keeping with current classification schemes, which recognize subtypes of low grade B-NHL as separate disease entities. Furthermore, our analysis demonstrates the power of laser capture microdissection in revealing molecular microheterogeneity in complex neoplasms.

Clonal evolution of B cells in transformation from low- to high-grade lymphoma

An outcome of low-grade B cell non-Hodgkins's lymphomas is the transformation to high-grade diffuse large B cell lymphomas (DLBL). To investigate the mechanisms of clonal evolution in the transformation to DLBL, we performed longitudinal molecular analyses of immunoglobulin (Ig), V(H)DJ(H) gene sequences expressed in cases of chronic lymphocytic leukemia (CLL), small lymphocytic lymphoma (SLL), and follicular lymphoma (FL) that transformed to DLBL. Among the neoplastic CLL and SLL cells and their respective high-grade transformants, there was no evidence for a clonotypic shift or acquired mutations in the expressed Ig V(H)DJ(H) gene segments, as further confirmed by a specific and sensitive PCR-single strand polymorphism analysis. In contrast, among the FL cells there was a high degree of intraclonal diversification with highly divergent V(H)DJ(H) gene sequences. Despite this intraclonal heterogeneity, the related DLBL expressed a collinear but unique V(H)DJ(H) gene sequence. The intraclonal genealogical tree for the FL case demonstrated that the DLBL emerged in association with unique V(H)DJ(H) gene mutational events. Among the intraclonal FL and related DLBL transformants, the nature and distribution of the Ig V(H)DJ(H) gene mutations were consistent with antigenic selection. Thus, clonal evolution in the transformation from low- to high-grade B cell lymphoma may involve distinct pathways which vary according to the cellular origin and the type of the progenitor B cell tumor.

Composite mantle-cell lymphoma and plasmacytoma

We report a case of a composite lymphoma comprising both mande cell lymphoma and a plasmacytoma. The two components were morphologically and immunohistochemically quite distinct. These properties, coupled with both direct and indirect molecular genetic evidence, suggest that these were two separate tumours occurring together by chance or by unknown oncogenic mechanisms, rather than clonally linked lymphomas.

Clinicopathologic study of PRAD1/cyclin D1 overexpressing lymphoma with special reference to mantle cell lymphoma. A distinct molecular pathologic entity

Mantle cell lymphomas (MCLs) are frequently associated with the overexpression of PRAD1/cyclin D1, activated by 11q13 translocation and its molecular counterpart BCL-1 gene rearrangement. We recently described the correlation of positive nuclear staining using monoclonal antibody against a PRAD1/cyclin D1 product with mRNA overexpression in MCLs. In the present study, we immunohistochemically investigated the PRAD1/cyclin D1 protein in a large series of 334 lymphoproliferative disorders, including 39 cases of MCLs on paraffin sections. Based on the cyclin D1 positivity, CD5 expression, and the morphologic features of the tumor tissue, four groups of MCL-related lesions were identified among the B-cell lymphomas examined: 36 cases with cyclin D1 overexpression, 35 (95%) of which exhibited CD5-positivity and MCL-morphology (Group 1); four cases of lymphomas with MCL morphology and CD5 expression but lacking cyclin D1 overexpression (Group II); four cases of lymphomas without cyclin D1 overexpression and surface CD5 but that fall within the morphologic boundaries of MCLs (Group III); and 11 cases of CD5-positive diffuse large cell lymphomas without cyclin D1 overexpression (Group IV). The Group I cases demonstrated quite homogeneous clinicopathologic features identical to those of MCLs. This group showed a poor prognosis (11% had 5-year survival), which is highly contrasted with that of Group II (100%). Although the four groups of MCL-related lesions sometimes overlapped in their histologic or phenotypic spectrums, each appeared to show distinct clinicopathologic and prognostic profiles. Our study provides a basis for further clarification of the nature of the neoplasms of Groups II, III, and IV. Moreover, this comprehensive study may indicate that the overexpression of PRAD1/cyclin D1 is biologically essential to defining MCLs.

Origin of high-grade lymphomas in Richter syndrome

Patients with B cell chronic lymphocytic leukemia (CLL) occasionally develop high-grade B cell lymphomas that are associated with constitutional symptoms, rapidly progressive lymphadenopathy, and swift clinical deterioration. Now known as Richter syndrome, this symptom complex develops in approximately 5% of all patients with CLL. Structural and molecular analysis of the immunoglobulin (Ig) genes have allowed investigators to define the clonal relationship between the leukemia and lymphoma cells of a given patient. In most cases the aggressive lymphoma evolves from the original leukemia cell clone. However, in some cases the lymphoma apparently represents a second malignancy. Differentiation between these two types of lymphoma may have clinical significance. Further investigation is required to allow for identification of CLL patients who are at risk for developing Richter syndrome and to understand factors involved in its etiopathogenesis.

Tumor suppressor genes and clonal evolution in B-CLL

This review highlights the genetic alterations that have been detailed in the malignant B-cell clones of patients with B-chronic lymphocytic leukemia (CLL). In particular, the alterations seen in p53 and the retinoblastoma (Rb) genes are reviewed. In addition, the multiplicity of cytogenetic alterations observed at baseline and on sequential analysis are summarized. The cytogenetic and molecular biologic analysis of B-CLL clones has revealed that there is a dynamic array of genetic events which occur within a B-cell clone. This latter data strongly suggests that clonal evolution may occur in B-CLL patients. However the relationship of the clonal instability to the patient's clinical course is still unclear. The relatively frequent detection of multiple tumor suppressor gene alterations in the B-CLL clones offer several interesting clues regarding the transformation event within B-CLL. A model is proposed which attempts to explain the potential contribution and interaction of p53 and Rb gene alterations in a malignant B-cell transformation.

Separate clones in concomitant multiple myeloma and a second B-cell neoplasm demonstrated by molecular and immunophenotypic analysis

The occurrence of multiple myeloma (MM) and a second B-cell neoplasm in the same patient is a rare event. We present 2 such patients, and provide evidence to support the presence of separate clones in these coexisting neoplasms. In the first case, MM became evident 14 months after the diagnosis of chronic lymphocytic leukemia (CLL). In past reports, most occurrences of this association, when investigated, have been regarded to be biclonal disease processes; however, with few exceptions, most were documented by immunologic studies alone. To establish the clonality in our case of CLL with MM, we examined both immunophenotypic data obtained by standard two-color flow cytometric analysis, and patterns of immunoglobulin gene rearrangement, using standard Southern analysis and hybridization with 32P-labelled JH and JK probes. This provided evidence for the presence in this patient of two separate monoclonal populations of B cells, manifested as light chain restrictions and gene rearrangements which differed in blood (CLL) and bone marrow (MM) samples. In the second case, MM presented simultaneously with bone marrow lymphocytosis and abnormal peripheral lymphocytes. Clonality studies on blood were not done. Bone marrow B-cell gene rearrangement studies, however, revealed the presence of three bands in the JK blot of significantly different intensities, suggestive of two monoclonal populations. A monoclonal population of small cells with surface B markers and surface IgM was demonstrated by flow cytometry, while a second population of larger cells with intracytoplasmic IgG matching the patient's serum monoclonal protein was detected by immunofluorescence microscopy. The results in these 2 cases expand previous findings of the rare association of MM with a second B-cell neoplasm, and demonstrate the usefulness of molecular diagnostic investigation.

Cytogenetic studies in patients with Richter's syndrome

Cytogenetic studies in six patients with Richter's syndrome (RS) showed complex chromosome abnormalities and chromosomal instability in five. No specific chromosomal abnormality was detected. Chromosomes 14 and 11 were the most frequently involved. Neither deletion of 13q14 nor complete trisomy 12 was observed. Two patients had structural rearrangement of 12q with t(5;12)(q21-q22;q23-q24). The involvement of this region of chromosome 12 may be significant, although not specific for chronic lymphocytic leukemia. These results were compared to those found in cytogenetically studied RS patients from the literature.

Serial phenotypic, cytogenetic and molecular genetic studies in Richter's syndrome: demonstration of lymphoma development from the chronic lymphocytic leukaemia cells

In this report we describe a unique longitudinal study on the clinical, phenotypic, cytogenetic and molecular genetic features of malignant cells from diagnosis of chronic lymphocytic leukaemia (CLL) to the development of lymphoma and lymphomatous meningitis. CLL cells at diagnosis were CD5+, CD19+, surface IgG+, kappa+, were karyotypically abnormal and showed clonal rearrangements in the immunoglobulin heavy (IgH) and kappa light chain genes. Phenotypically leukaemic cells and lymphoma cells at RS resembled CLL at diagnosis, but showed cytogenetic evolution. Geometrically leukaemic cells and lymphoma cells retained the initial clonal rearrangements in IGH and kappa genes, but showed additional supervening clonal rearrangements in both of these genes as the disease progressed to RS. Furthermore, the c-lambda DNA showed clonal rearrangements in the leukaemic cells and lymphoma cells at RS. This complete phenotypic and genotypic analysis of tumour cells during the course of the disease demonstrates the origin of lymphoma from CLL cells through progressive cytogenetic and molecular genetic changes in CLL cells.

Clonal heavy chain isotype switching within the proliferation centers of a small lymphocytic lymphoma: implications regarding the origin of proliferation centers

We describe an unusual case of small lymphocytic lymphoma with multiple prominent pseudofollicular proliferation centers in which immunohistochemistry reveals that the small cells are surface IgM kappa positive and the large pseudofollicular cells are surface IgA kappa positive. We further show by genomic DNA analysis that the tumor tissue contains two JH rearrangements, one Cmu rearrangement, one C alpha rearrangement, and a single C kappa rearrangement, strongly suggesting that the large cells within the proliferation centers have arisen from the small cells via a clonal heavy chain immunoglobulin isotype switch. Isotype switching in human lymphoma and leukemia appears to be an uncommon event. However, there are reports that strongly support isotype switching in pre-B-cell leukemia, Richter's syndrome, lymphoid blast crisis of chronic myelogenous leukemia, and multiple myeloma. To our knowledge, there have been no previous reports demonstrating isotype switching within the proliferation centers of small lymphocytic lymphoma. We present evidence of in vivo intratumoral isotype switching within the proliferation centers of a small lymphocytic lymphoma documented at the level of immunohistochemistry and DNA rearrangement.

Heterogeneous immunoglobulin gene rearrangement in a B-chronic lymphocytic leukemia progressing into non-Hodgkin lymphoma (Richter syndrome)

BACKGROUND

The relationship between chronic lymphocytic leukemia (CLL) and supervening non-Hodgkin lymphoma is debated, as is whether a particular genomic pattern is related to the emergence of the terminal lymphoma. To investigate these features, the molecular organization of the immunoglobulin (Ig) gene region in a case during both the B-CLL and Richter transformation phase was studied.

METHODS

B-CLL and non-Hodgkin lymphoma cells were processed for Southern blot analysis of Ig heavy- and light-chain gene configuration.

RESULTS

Molecular studies of B-CLL cells revealed the presence of a single Ig heavy-chain rearrangement with both kappa and lambda light-chain rearranged genes, which was consistent with the occurrence of multiple mutational events during the development of the B-CLL clone. Molecular analysis of the lymphoma DNA showed new Ig heavy- and kappa light-chain rearrangements in addition to the original ones related to the CLL phase, indicating that the lymphoma tissue consisted of two genotypically distinct populations of cells.

CONCLUSIONS

On the basis of the overall molecular configuration, this heterogeneous pattern of Ig gene rearrangement was interpreted as an inherent genetic instability of the CLL clone, in which multiple mutational events allowed a selective pressure toward more aggressive subclones, resulting in the emergence of the terminal lymphoma.

Phenotypic and genotypic lineage switch of a lymphoma with shared chromosome translocation and T-cell receptor gamma gene rearrangement

A case of non-Hodgkin's lymphoma showed a phenotypic and genotypic cell lineage switch twice during nine years of his clinical history; first, T-cell type, pleomorphic small cell lymphoma developed, followed by B-cell type, diffuse centroblastic/centrocytic lymphoma, and finally T-zone lymphoma without follicles again developed, from which AST-1 cultured cell line was established. Karyotype analysis demonstrated a shared abnormal chromosome, der(1)t(1;?)(p36;?), among the first relapsed B-cell tumor, the second relapsed T-cell tumor and AST-1 cell line. Furthermore, T-cell receptor (TCR) gamma gene rearrangement bands of the same size were observed in the first relapsed B-cell tumor and the second relapsed T-cell tumor as well as AST-1 cell line. These results suggested that both relapsed tumors of different cell lineages are derived from a common malignant clone, presumably a committed lymphoid stem cell. A unique translocation, t(2;14)(q37;q11.2), which may involve TCR delta/alpha gene complex, was observed in the second relapsed tumor and AST-1 cells. To attempt to isolate the breakpoint of this translocation, the configuration of TCR delta/alpha gene complex was studied. The result showed that two rearrangements of TCR alpha gene detected with J alpha probes were the products of the normal TCR rearrangement process, and were not involved in the translocation at this region. This patient, together with the AST-1 cell line, provided us a unique opportunity to study the development and clonal evolution of malignant lymphoma.

Regulatory aspects of clonally expanded B-1 (CD5+ B) cells

B-1 (CD5+ B) cells appear early in ontogeny, produce mainly unmutated polyreactive antibodies, and are capable of self-renewal. B-1 cells clonally expand with age and are the malignant cell in chronic lymphocytic leukemia. In this report immunological analysis of B-1 malignancies in NZB mice, a murine model of chronic lymphocytic leukemia, is related to current information on B-1 cells. B-1 clones from NZB mice produce high levels of interleukin-10, detected at the RNA level by semi-quantitative polymerase chain reaction. In addition, the B-1 malignant clones in NZB mice and their hybrids, are negative for B220/6B2 expression, the B-specific antigenic form of CD45 which is a membrane-associated phosphatase involved in lymphocyte activation. Both the autocrine production by B-1 cells of interleukin-10 and altered CD45 expression may be responsible for the clonal expansion of these cells, as well as the accompanying T cell expansion. We report the establishment of an in vitro cytotoxic CD8+ T cell line derived from an NZB with a B-1 malignancy. The effect of B-1 cell-derived interleukin-10 on subsets of T lymphocytes may account for the immunoregulatory properties of B-1 cells. In addition, the NZB malignancies were also characterized for immunoglobulin variable region sequence and antigen specificity. The B-1 malignancies produced immunoglobulin derived from unmutated germline sequences with no N base substitutions. It appears that both the immunoglobulin and interleukin-10 produced by the B-1 malignant cell in NZB mice may have immunoregulatory properties. A study of B-1 malignancies may shed light on the immunoregulatory properties of non-clonally expanded normal B-1 cells.

The role of clonal selection in the pathogenesis of an autoreactive human B cell lymphoma

To study the association of autoimmunity and human B cell neoplasia, we have established a model of a B cell lymphoma which expresses a pathogenic autoantibody of defined specificity. The Ig VH gene expressed in this neoplasm was analyzed longitudinally using clinical specimens taken from the splenic lymphoma (S) at diagnosis and from lymph node relapses 3 and 4 yr later (N3 and N4). Southern analysis and oligonucleotide hybridization experiments demonstrated that clonally related predominant and minor tumor cell populations were present in S at diagnosis, and that the minor population became the predominant population in the relapse specimens, N3 and N4. Although the Ig specificity and idiotype were the same at diagnosis and at both relapses, analysis of the expressed VH gene sequences showed 14 base changes between S and N3, and 2 further changes at N4. Little sequence heterogeneity was observed at each sampling time, indicating that the ongoing mutation frequency was low. The relevant germline precursor VH gene was determined from autologous germline DNA and compared to the expressed genes. Based on the pattern of shared and unshared mutations, we were able to establish the genealogic relationship of the germline VH gene and the expressed clonotypes of S, N3 and N4. Taken together, the findings from Southern blotting, oligonucleotide hybridization, and sequence analysis permit us to describe a molecular aspect of tumor progression, "clonotypic shift", wherein subpopulations of the malignant clone, marked by different V gene clonotypes, emerge and predominate at different time points in the evolution of the lymphoma. Furthermore, the sequential and nonrandom pattern of the VH mutations, correlated with the observed conservation of autospecificity and idiotype, implies that clonal selection may have influenced the pathogenesis of the lymphoma.