Mediastinal large B-cell lymphoma: clinical and immunohistological findings in 18 patients treated with different third-generation regimens

CD30+ Lymphoproliferative Disorders as Potential Candidates for CD30-Targeted Therapies

CONTEXT.—

In the early 1980s, a monoclonal antibody termed Ki-1 was developed against a cell line derived from a patient with Hodgkin lymphoma. This antibody detected a limited number of benign activated lymphocytes in lymphoid tissue, whereas in Hodgkin lymphoma it appeared to be nearly specific for Reed-Sternberg cells and their mononuclear variants. Subsequent studies showed that Ki-1 expression defined a new type of lymphoma that was later designated anaplastic large cell lymphoma with or without anaplastic large cell kinase expression/translocation. In the past 30 years, numerous new lymphoma entities have been defined, many of which are variably positive for CD30. Many virally transformed lymphoproliferative disorders are also frequently positive for CD30.

OBJECTIVE.—

To illustrate the broad spectrum of CD30+ hematologic malignancies and to provide an update of CD30-targeted therapies.

DATA SOURCES.—

Personal experiences and published works in PubMed.

CONCLUSIONS.—

Because of its low expression in normal tissue, CD30 was studied as a therapeutic target for many years. However, the first functional humanized antibody against CD30 was developed only about 10 years ago. Brentuximab vedotin is a humanized anti-CD30 antibody linked to a cytotoxin, and was approved by the US Food and Drug Administration in 2012 for treating refractory Hodgkin lymphoma and anaplastic large cell lymphoma. Since then, the list of Food and Drug Administration-approved CD30-targeted hematologic malignancies has grown. Recently, the therapies using tumor antigen-specific chimeric antigen receptor T cells targeting CD30 have incited a great deal of enthusiasm and are studied in clinical trials.

Expecting the unexpected - Primary mediastinal large B cell lymphoma presenting as huge lung parenchymal mass

The first possibility considered in the etiology of large lung masses is neoplastic lesions. The differential diagnoses of these masses include bronchogenic carcinoma, pulmonary sarcoma, primitive neuroectodermal tumor etc. Primary or secondary pulmonary parenchymal lymphomas presenting as large mass is distinctly rare. We share the case of a young lady who presented with a large left lung mass almost entirely replacing the left lung parenchyma, with associated intrathoracic lymphadenopathy. On evaluation she was proved to have primary mediastinal large B-cell lymphoma. Treatment with an aggressive chemotherapy regimen led to complete remission of the parenchymal and nodal disease. The uncommon radiological presentation and the excellent therapeutic response despite huge tumor load merit clinical attention.

MiRNA Dysregulation in Childhood Hematological Cancer

For decades, cancer biology focused largely on the protein-encoding genes that have clear roles in tumor development or progression: cell-cycle control, apoptotic evasion, genome instability, drug resistance, or signaling pathways that stimulate growth, angiogenesis, or metastasis. MicroRNAs (miRNAs), however, represent one of the more abundant classes of cell modulators in multicellular organisms and largely contribute to regulating gene expression. Many of the ~2500 miRNAs discovered to date in humans regulate vital biological processes, and their aberrant expression results in pathological and malignant outcomes. In this review, we highlight what has been learned about the roles of miRNAs in some of the most common human pediatric leukemias and lymphomas, along with their value as diagnostic/prognostic factors.

Current trends in the treatment of primary mediastinal large B-cell lymphoma - an overview

Primary mediastinal large B-cell lymphoma has been recognised as a distinct entity with unique clinical, pathologic, and genetic features. According to WHO 2008 classification it is marked as a variant of diffuse large B-cell lymphoma but shares characteristics with classic Hodgkin lymphoma. Genetic analysis has shown that amplification of the 9p24.1 region is the disease's specific structural alteration. Aggressive behaviour and a tendency to invade surrounding tissues of the thoracic cavity, often causing superior vena cava syndrome, or pleural or pericardial effusions, are the clinical hallmarks of this disease. For a long period of time it has been considered as a disease with poor prognosis, which responds poorly to the conventional treatment created for diffuse large B-cell lymphoma. An elective treatment has not yet been established, but recently the situation has became much more favourable. After the introduction of rituximab the cure rates have risen to over 80%, and the most recent results have demonstrated a new insight with dose-adjusted intensified continuous treatments, in which the cure rates have exceeded 90%. Current trends have led to the introduction of dose-adjusted intensified protocols becoming a standard of care, whereas the use of radiotherapy remains controversial because of the questionable predictive value of post-treatment PET/CT validity. The relapse rate is very low after two years of sustained complete remission. If the disease relapses or is resistant the outcome is very poor regardless of the applied treatment modality.

Surface Light Chain Expression in Primary Mediastinal Large B-Cell Lymphomas by Multiparameter Flow Cytometry

OBJECTIVES

Primary mediastinal large B-cell lymphoma (PMLBL) is an aggressive B-cell lymphoma typically localized to the mediastinum. To date, no study has undertaken a comprehensive analysis of this entity by multiparameter flow cytometry.

METHODS

Cases of PMLBL with diagnostic flow cytometry were identified from pathology databases of Boston Children's Hospital, Brigham and Women's Hospital, and Stanford Hospital.

RESULTS

Most of these patients with PMLBL were women with a median age of 30 years who had stage 1 disease that lacked bone marrow involvement. By flow cytometry, 50% of all PMLBLs showed restricted surface immunoglobulin expression. When comparing patients with PMLBL by the absence or presence of surface light chain immunoglobulins, no differences were seen in the morphologic appearance; expression of CD23, CD30, or CD10; age at presentation; or clinical stage (P > .5 for all). In addition, both groups showed similarly good survival outcomes and were alive at last follow-up (11/14 [79%]; P = .542).

CONCLUSIONS

This multi-institutional study demonstrates that 50% of PMLBLs can present with clonal surface light chain expression and that PMLBL is more immunophenotypically diverse than previously described. Furthermore, our findings suggest that the absence or presence of surface light chains should not be used as criteria for diagnosis in this disease.

Single-institution experience in the treatment of primary mediastinal B cell lymphoma treated with immunochemotherapy in the setting of response assessment by 18fluorodeoxyglucose positron emission tomography

PURPOSE

Excellent outcomes obtained after infusional dose-adjusted etoposide, doxorubicin, cyclophosphamide, vincristine, prednisone, and rituximab (R-EPOCH) alone have led some to question the role of consolidative radiation therapy (RT) in the treatment of primary mediastinal B cell lymphoma (PMBL). We reviewed the outcomes in patients treated with 1 of 3 rituximab-containing regimens (cyclophosphamide, doxorubicin, vincristine, prednisone [R-CHOP]; hyperfractionated cyclophosphamide, vincristine, doxorubicin and dexamethasone [R-HCVAD], or R-EPOCH) with or without RT. We also evaluated the ability of positron emission tomography-computed tomography (PET-CT) to identify patients at risk of relapse.

METHODS AND MATERIALS

We retrospectively identified 97 patients with diagnoses of stage I/II PMBCL treated at our institution between 2001 and 2013. The clinical characteristics, treatment outcomes, and toxicity were assessed. We analyzed whether postchemotherapy PET-CT could identify patients at risk for progressive disease according to a 5 point scale (5PS) Deauville score assigned.

RESULTS

Among 97 patients (median follow-up time, 57 months), the 5-year overall survival rate was 99%. Of patients treated with R-CHOP, 99% received RT; R-HCVAD, 82%; and R-EPOCH, 36%. Of 68 patients with evaluable end-of-chemotherapy PET-CT scans, 62% had a positive scan (avidity above that of the mediastinal blood pool [Deauville 5PS = 3]), but only 9 patients experienced relapse (n=1) or progressive disease (n=8), all with a 5PS of 4 to 5. Of the 25 patients who received R-EPOCH, 4 experienced progression, all with 5PS of 4 to 5; salvage therapy (RT and autologous stem cell transplantation) was successful in all cases.

CONCLUSION

Combined modality immunochemotherapy and RT is well tolerated and effective for treatment of PMBCL. A postchemotherapy 5PS of 4 to 5, rather than 3 to 5, can identify patients at high risk of progression who should be considered for therapy beyond chemotherapy alone after R-EPOCH.

Primary mediastinal lymphoma: diagnosis and treatment options

Primary mediastinal large B-cell lymphoma (PMBCL) is a unique B-cell lymphoma variant that arises from a putative thymic medulla B cell. It constitutes 2-4% of non-Hodgkin lymphomas and occurs most frequently in young females. PMBCL is characterized by a diffuse proliferation of medium-to-large B cells associated with sclerosis. Molecular analysis shows that PMBCL is a distinct entity compared to other types of diffuse large B-cell lymphomas. PMBCL is characterized by a locally invasive anterior mediastinal bulky mass. The combination of rituximab with CHOP/CHOP-like regimens followed by mediastinal radiation therapy (RT) is associated with a 5-year progression-free survival of 75-85%. However, the role of consolidation RT still remains uncertain. More intensive regimens, such as DA-EPOCH-R without mediastinal RT, have shown very promising results. The conclusive role of PET-CT scan requires prospective studies and there is hope that this may allow to de-escalate RT and accordingly yield reliable prognostic information.

Brentuximab vedotin in systemic T-cell lymphoma

INTRODUCTION

Brentuximab vedotin is an antibody-drug conjugate which consists of the anti-CD30 monoclonal antibody cAC10 conjugated with the cytotoxic agent monomethyl auristatin E (MMAE). Brentuximab vedotin has been approved by the US Food and Drug Administration for the treatment of relapsed or refractory Hodgkin's lymphoma (HL) and anaplastic large cell lymphoma (ALCL). The efficacy of brentuximab vedotin in other CD30(+) lymphomas is currently being investigated.

AREAS COVERED

In this paper, we review the currently available treatment options for systemic peripheral T-cell lymphomas (PTCL) and the role of brentuximab vedotin in relapsed or refractory ALCL. In addition, ongoing clinical trial of brentuximab vedotin in relapsed PTCL and combination therapy with other chemotherapies for initial treatment of CD30 lymphoma will also be reviewed.

EXPERT OPINION

Brentuximab vedotin has established its role in the treatment of relapsed or refractory HL and ALCL. In the next few years, the efficacy of this agent in other CD30(+) lymphomas will be described. The safety and efficacy of several brentuximab-based combination regimens, including use as frontline chemotherapy is under investigation.

Primary mediastinal DLBCL: evolving biologic understanding and therapeutic strategies

Primary mediastinal diffuse large B-cell lymphoma is a quite rare clinicopathologic entity. Molecular analysis shows it to be distinct from other types of diffuse large B-cell lymphoma, and some retrospective analyses suggests that it may respond better to third-generation chemotherapy regimens than to the more commonly used CHOP. The addition of rituximab could reduce these differences; the role of consolidation with local radiotherapy, which is often used to treat residual mediastinal masses, remains. The real role of FDG-PET scanning requires prospective studies, and it is hoped that this may allow the de-escalation of radiation therapy accordingly to yield reliable prognostic information.

The molecular pathogenesis of primary mediastinal large B-cell lymphoma

Primary mediastinal large B-cell lymphoma (PMBCL) is a recognized non-Hodgkin lymphoma entity with unique pathologic, clinical, and molecular characteristics distinct from those of other diffuse large B-cell lymphomas. Immunohistochemical characterization and molecular studies strongly suggest that PMBCL is of germinal center or postgerminal center origin. Pivotal gene expression profiling work defined major deregulated pathway activities that overlap with Hodgkin lymphoma and prompted a more detailed analysis of candidate genes. In particular, the nuclear factor-κB and the Janus Kinase-Signal Transducer and Activator of Transcription signaling pathways are targeted by multiple genomic hits, and constitutive activity of both pathways can be considered molecular hallmark alterations of PMBCL. Moreover, data are emerging giving unique insight into remodeling of the epigenome that affects transcriptional regulation of a multitude of genes. More recently, the tumor microenvironment of PMBCL has shifted into focus based on a number of gene perturbations altering expression of surface molecules that contribute to immune escape. These findings highlight the importance of immune privilege in the pathogenesis of PMBCL and suggest that disrupting crosstalk between the tumor cells and the microenvironment might be a rational new therapeutic target in conjunction with traditional treatment strategies.

Prognostic impact of MUM1 expression by immunohistochemistry on primary mediastinal large B-cell lymphoma

Diffuse large B-cell lymphoma can be classified into two prognostically distinct subgroups with germinal center B-cell-like (CG) and activated B-cell-like (post-CG) characteristics, based on CD10, BCL-6, and MUM1 expression. We performed a retrospective analysis of the clinical variables of 37 patients with primary mediastinal large B-cell lymphoma and the expression of BCL-6 and MUM1 in 22 patients with available tissue. The median age was 30 years, and 70% of the patients were female. BCL-6 and MUM1 were expressed in 64% and 45% of cases, respectively. Five-year overall survival (OS) and disease-free survival (DFS) were 47% and 81%, respectively. In univariate analysis, complete response (p = 0.0001), radiation therapy (p = 0.01), International Prognostic Index (p = 0.001), and MUM1 expression (p = 0.002) correlated with OS. For this group of patients with homogeneous clinical characteristics, response to initial chemotherapy and MUM1 expression were associated with prognosis.

TRAF1 is involved in the classical NF-kappaB activation and CD30-induced alternative activity in Hodgkin's lymphoma cells

TNFR-associated factors (TRAFs) participate in diverse biological processes, such as adaptive and innate immunity, stress response, and bone metabolism. We report that all TRAFs except TRAF3 are expressed at mRNA and protein levels in B cell-derived Hodgkin's lymphoma cell lines (L428 and KM-H2). Both the classical (p50-RelA) and the alternative NF-kappaB activity (p52-RelB) are sustained in L428 and KM-H2 cells. A successful depletion of TRAF1 protein expression by means of RNA interference abrogates the anti-apoptosis activity in L428 cells. The TRAF1-deficiency reduces the classical NF-kappaB activity but not the alternative activity. The expression of the NF-kappaB targeting genes, such as ICAM-1, c-Flip, and Cyclin D1, is suppressed in the TRAF1-depleted cells. On the other hand, CD30 signaling upregulates the TRAF1 expression while reducing the expression of TRAF2 and TRAF5. Importantly, the CD30-induced alternative NF-kappaB activation is inhibited by the depletion of the TRAF1 expression. We also demonstrate that the phosphorylation of the extracellular signal-regulated kinase (ERK) upon CD30 stimulation in Hodgkin's lymphoma cells is independent of TRAF1 expression. Our data shed new light on the function of TRAF1 in B cell-derived lymphoma cells. We conclude that TRAF1 is an important molecule mediating both the CD30 signaling-dependent and independent NF-kappaB activation, which prevents the lymphoma cells from spontaneous and induced apoptosis.

Primary mediastinal B-cell lymphoma in the pediatric patient: Can a rational approach to therapy be based on adult studies?

The literature on adult and pediatric primary mediastinal B-cell lymphoma (PMBCL) was reviewed and compared. Biologically, adult PMBCL has more similarities to Hodgkin Lymphoma (HL) than diffuse large B-cell lymphoma (DLBCL). Pediatric studies suggest that the biology is similar to that in adults. Median age of children is 14.3 years and the overall survival (OS) is reported as 78.6% and event-free survival (EFS) as 67.4%. Adverse prognostic factors included LDH >500 and mass size over 10 cm, with a trend towards better survival in younger patients. Studies in adults show better survival with intensified chemotherapy and the addition of rituximab. Data on the use of radiation therapy show improved CR rates and survival with addition of involved field radiation therapy (IFRT). Positron emission tomography (PET) with computerized tomography (CT) imaging response-assessment after two courses and at therapy-end may allow for the rational use of IFRT in pediatric/adolescent patients who are more susceptible to development of adverse late effects.

Primary mediastinal B-cell lymphoma: treatment and therapeutic targets

Primary mediastinal B-cell lymphoma (PMBCL) is a recognised subtype of diffuse large B-cell lymphoma according to the WHO classification that represents approximately 5% of aggressive lymphomas, and 2% of all cases of lymphomas. It presents with unique clinical, morphologic and immunophenotypic characteristics that define the disease. Retrospective studies have found that PMBCL patients have excellent survival rates with a distinct plateau and a trend to better outcome if treated with dose-intensified chemotherapy with MACOPB or VACOPB. In spite of the multiple molecular data known, generated on the pathogenesis of this tumour, treatment is still essentially based on a combination of chemo and immunotherapy. We take this opportunity for reviewing the recent biologic data provided by gene expression profiling of the tumour, for discussing new potential therapeutic targets.

Extranodal lymphoma

Lymphomas arising in extranodal sites are intriguing. The types of lymphomas encountered vary widely from one extranodal site to another. For many types of extranodal lymphomas, there are distinctive clinicopathologic features, sometimes including association with an underlying immunodeficiency syndrome, autoimmune disease, infection, or other immunologic disorder, or a predilection to affect patients of certain ethnic origins. Presented below is a review of lymphomas that are encountered most often in extranodal sites.

Constitutive overexpression of a novel 21 kDa protein by Hodgkin lymphoma and aggressive non-Hodgkin lymphomas

Background

CD30, a 120 kDa surface phosphorylated protein is a member of tumour necrosis/nerve growth factor receptor (TNF/NGFR) family and constitutively expressed by Hodgkin and Reed-Sternberg (HRS) cells of Hodgkin lymphoma (HL) and the neoplastic cells of Anaplastic Large Cell Lymphoma (ALCL). A disease-specific protein marker is yet to be identified in Hodgkin lymphoma cells. In order to define HL-specific biomarkers, novel murine monoclonal antibodies were developed in our laboratory.

Results

Murine monoclonal antibodies (mabs) were raised against the B3 sub clone of HL-derived cell line KM-H2. Two of these mabs (clone R23.1 mab and clone R24.1 mab) are IgG₁ class antibodies that recognize a 21 kDa protein present at the cell membrane and in the cytoplasm in HL-derived cell lines. Clone R24.1 mab recognizes a formalin-resistant epitope and labels HRS cells in tissue samples from patients with HL of the classical type, ALCL, and subsets of T and B cell aggressive Non-Hodgkin Lymphomas (NHL). The antigen recognized by the clone R23.1 mab and clone R24.1 mab does not share epitopes with CD30 cluster regions A, B, or C, and, unlike CD30, is not expressed by phytohemagglutinin (PHA) activated T cells.

Conclusion

The 21 kDa protein detected by clone R23.1 and clone R24.1 mabs is a novel membrane-associated protein that may be a potential marker for the diagnosis and targeted therapy of HL and aggressive T and B cell NHL.

Primary Mediastinal Large B-Cell Lymphoma: Results of Intensive Chemotherapy Regimens (MACOP-B/VACOP-B) Plus Involved Field Radiotherapy on 53 Patients. A Single Institution Experience

PURPOSE

The optimal therapy for primary mediastinal large B-cell lymphoma (PMLBCL) remains undefined. The superiority of intensive chemotherapy regimens (Methotrexate, Doxorubicin, Cyclophosphamide, Vincristine, Prednisone, Bleomycin [MACOP-B]/Etoposide, Doxorubicin, Cyclophosphamide, Vincristine, Prednisone, Bleomycin [VACOP-B]) over Cyclophosphamide, Doxorubicin, Vincristine, Prednisone (CHOP)-like chemotherapy is upheld by some authors. The role of radiotherapy is still debated. In the absence of randomized trials, we report clinical findings and treatment response in 53 consecutive patients treated with intensive chemotherapy and mediastinal involved-field radiation therapy (IFRT).

METHODS AND MATERIAL

Fifty-three consecutive patients with PMLBCL were retrospectively analyzed. Planned treatment consisted of induction chemotherapy (I-CT; Prednisone, Methotrexate, Doxorubicin, Cyclophosphamide, Etoposide-Mechloroethamine, Vincristine, Procarbazine, Prednisone [ProMACE-MOPP] in the first 2 patients, MACOP-B in the next 11, and VACOP-B in the last 40) followed by IFRT. Planned treatment was concluded in 43 of 53 patients; in 10 patients, I-CT was not immediately followed by IFRT. Among these 10 patients, 6 received high-dose chemotherapy (HD-CT) followed by IFRT, 2 received HD-CT, and 2 received no further treatment.

RESULTS

After a median follow-up of 93.9 months (range, 6-195 months), 45 of 53 patients (84.9%) were alive without disease. Eight patients died: 7 of PMLBCL and 1 of toxicity during HD-CT. The 5-year disease-free survival (DFS) and overall survival rates were 93.42% and 86.6%, respectively. The response rates after I-CT were complete response (CR) in 20 (37.73%) and partial response (PR) in 30 (56.60%); 3 patients (5.66%) were considered nonresponders. Among patients in PR after chemotherapy, 92% obtained a CR after IFRT.

CONCLUSIONS

Our report confirms the efficacy of intensive chemotherapy plus mediastinal IFRT. IFRT plays a pivotal role in inducing CR in patients in PR after chemotherapy.

Primary mediastinal B-cell lymphoma

Primary mediastinal B-cell lymphoma (PMBCL) is a sub-type of the heterogeneous diffuse large B-cell lymphoma category, and comprises approximately 5% of all non-Hodgkin's lymphomas (NHL). It was first recognized as a distinct clinico-pathologic entity 20 years ago, and recent work has further characterized specific molecular features. Gene expression profiling has suggested a partial overlap with nodular sclerosing Hodgkin lymphoma (HL), with which it shares some clinical features. The optimal management remains a matter of debate. There is uncertainty as to whether weekly alternating chemotherapy regimens may be more effective than CHOP, whether consolidation radiotherapy (RT) to the mediastinum is always required, whether PET scanning can be used to determine this, and whether the use of rituximab as part of initial therapy will change the answers to these questions. The International Extranodal Lymphoma Study Group (IELSG) 26 clinicopathologic study of PMBCL, which has recently opened, represents a first attempt to gather data prospectively on some of these issues.

Primary Mediastinal Large B-Cell Lymphoma: A Single-Center Study of Clinicopathologic Characteristics

Primary mediastinal large B-cell lymphoma (PMLBCL) is a subset of LBCL with unique clinicopathologic features. Some studies have raised the question of differences in biological features and clinical course among patients from different parts of the world. We conducted a retrospective clinicopathologic analysis of 24 patients with PMLBCL from a single center in Croatia. We also conducted the first investigation of the frequency of lymphotropic viruses human herpesvirus 6 (HHV-6) and HHV-8 in lymphoid lesions of this disease. The clinical characteristics of the patients were as expected, with high International Prognostic Index scores, elevated serum lactate dehydrogenase (LDH) levels, and bulky disease being adverse prognostic factors. Only 6 patients (25%) showed CD30 expression, and Bcl-6 protein expression was, in our series, prognostically favorable (P = .0401). One patient's tumor had detectable HHV-6 genome sequence, but no HHV-8 sequences were detected in any tumors. Two thirds of the patients received CHOP chemotherapy (cyclophosphamide, hydroxydaunomycin, vincristine, and prednisone) with a relatively low complete remission rate (43.8%; median follow-up, 33.8 months). This study confirmed the moderate preponderance among PMLBCL patients of young females with B symptoms and elevated LDH levels. The CHOP regimen proved effective as first-line therapy only in patients with limited disease. Therefore, other third-generation chemotherapy protocols may be considered for treatment, especially in patients with bulky and advanced disease.

Mediastinal gray zone lymphoma: the missing link between classic Hodgkin's lymphoma and mediastinal large B-cell lymphoma

In recent years, overlap in biologic and morphologic features has been identified between classic Hodgkin lymphoma (cHL) and B-cell non-Hodgkin lymphoma. Nevertheless, the therapeutic approaches for these diseases remain different. We undertook a study of "mediastinal gray zone lymphomas" (MGZL), with features transitional between cHL nodular sclerosis (NS) and primary mediastinal large B-cell lymphoma (MLBCL) to better understand the morphologic and immunophenotypic spectrum of such cases. Twenty-one MGZL cases were identified over a 20-year period. We also studied 6 cases of composite or synchronous lymphoma with two distinct components at the same time (cHL-NS and MLBCL) and 9 sequential cases with MLBCL and cHL-NS at different times. All patients had a large mediastinal mass. Immunohistochemical studies focused on markers known to discriminate between cHL and MLBCL, including B-cell transcription factors. VJ-PCR was performed in 8 cases to look at clonality of the immunoglobulin heavy chain gene (IgH). Of the gray zone cases, 11 had morphology reminiscent of cHL-NS, but with unusual features, including a large number of mononuclear variants, diminished inflammatory background, absence of classic Hodgkin phenotype, and strong CD20 expression (11 of 11). Ten cases had morphology of MLBCL, but with admixed Hodgkin/Reed-Sternberg and lacunar cells, absent (3 of 10) or weak (7 of 10) CD20 expression, and positivity for CD15 in 7 cases. B-cell transcription factor expression in the gray zone cases more closely resembled MLBCL than cHL with expression of Pax5, Oct2, and BOB.1 in all but 1 case studied (14 of 15). MAL staining was found in 7 of 10 MGZL, and in at least one component of 6 of 7 evaluable composite or sequential MLBCL/cHL cases. Two cases of sequential lymphoma showed rearrangements of the IgH gene of identical size: one in which MLBCL was the first diagnosis and one in which MLBCL was diagnosed at relapse, indicating clonal identity for the two components of cHL and MLBCL. There is accumulating evidence that MLBCL and cHL are related entities. Further support for a relationship between MLBCL and cHL-NS is provided by composite and metachronous lymphomas in the same patient, as well as the existence of MGZL with transitional morphology and phenotype.

Pneumomediastinum as a complication to treatment of mediastinal (thymic) large B-cell lymphoma

Mediastinal (thymic) large B-cell lymphoma (Med-DLBCL) is a subtype of diffuse large B-cell lymphomas (DLBCL) with a typical radiological appearance of bulky anterior mediastinal mass, often with areas of necrosis. We report a case of Med-DLBCL with unusual radiological findings and clinical development. Computed tomography (CT) obtained at presentation revealed a huge anterior mediastinal tumor with an axial diameter of 180 mm. Nineteen days after the first cycle of chemotherapy, chest radiography and CT revealed large areas of tumor necrosis and pneumomediastinum with air-fluid levels. To our knowledge, air-fluid levels inside Med-DLBCL have not been previously described. This finding, in combination with necrotic sputum, may indicate communication between the tracheobronchial tree and the tumor.

Primary mediastinal B-cell lymphoma with sclerosis: report of 11 cases treated with intensified-CHOP plus radiotherapy

Primary mediastinal B-cell lymphoma (PMBCL) is a clinicopathological entity with aggressive behavior. Retrospective evaluation suggests the need for intensive chemotherapy programs. From 1997 to February 2003, a total of 11 cases of previously untreated PMBCL with sclerosis were treated at our institution with 5 courses of intensified CHOP (ICHOP) regimen and mediastinal irradiation. Three patients were submitted to high-dose chemotherapy with peripheral-blood stem-cell support, followed by radiotherapy, because of intermediate-risk age-adjusted International Prognostic Index at diagnosis. After a median follow up of 30 months, all patients but one are in continuous complete remission (CR), and overall survival is 100%.

Primary Mediastinal Large B-Cell Lymphoma: A Single-Institution Clinical Study in Japan

Several clinicopathologic studies of primary mediastinal large B-cell lymphoma (Med-DLBCL) have been reported from Western countries; however, only a few series of at most 10 cases are available in Japan. To further clarify the Med-DLBCL occurring in Japan, we analyzed the clinical features of 28 patients with Med-DLBCL diagnoses who were treated at the National Cancer Center Hospital between 1982 and 2002. The median age was 37 years (range, 18-80 years). The ages of 16 male patients ranged widely from 18 to 80 years, whereas the 12 female patients appeared to show a single age peak at 20 to 40 years. Only 13 patients (46%) achieved a complete response with initial treatments, mostly by CHOP-like regimens (cyclophosphamide, doxorubicin, vincristine [Oncovin], and prednisolone) followed by radiotherapy. The estimated 3-year overall and failure-free survival rates were 32% and 33%, respectively, indicating the relatively unfavorable prognosis of the patients in our series. The following factors were found to be significantly associated with shortened survival prospects: age >60 years, serum lactate dehydrogenase level greater than normal, performance status >1, and presence of bulky mediastinal mass. In conclusion, the clinical features of Japanese patients with Med-DLBCL may be different from those with the disease in Western countries. Because this investigation was a single-institution study with a limited number of patients, however, multicenter confirmatory studies are needed.

Primary mediastinal large B-cell lymphoma (PMLBCL): long-term results from a retrospective multicentre Italian experience in 138 patients treated with CHOP or MACOP-B/VACOP-B

The optimal treatment of primary mediastinal large B-cell lymphoma (PMLBCL) is still undefined. In the absence of randomised studies, we retrospectively analysed: (a) the effectiveness of two chemotherapy regimens (CHOP vs MACOP-B/VACOP-B) in complete remission (CR) achievement and event-free survival (EFS) and (b) the role of mediastinal involved-field radiotherapy (IF-RT) as consolidation. From 1982 to 1999, 138 consecutive patients affected by PMLBCL were treated in 13 Italian institutions with CHOP (43) or MACOP-B/VACOP-B (95). The two groups of patients were similar as regard to age, gender, presence of bulky mediastinal mass, pleural effusion, stage and international prognostic indexes category of risk. Overall, 75.5% of patients in CR received IF-RT as consolidation. Complete remission was 51.1% in the CHOP group and 80% in MACOP-B/VACOP-B (P<0.001). Relapse occurred in 22.7% of CHOP- and in 9.2% of MACOP-B/VACOP-B-treated patients (n.s.). Event-free patients were 39.5% in CHOP and 75.7% in the MACOP-B/VACOP-B group (P<0.001). The addition of IF-RT as consolidation improved the outcome, irrespectively of the type of chemotherapy (P=0.04). At a multivariate analysis, achievement of CR (P<0.0001) and type of CT (MACOP-B/VACOP-B) retained the significance for OS (P=0.008) and EFS (P=0.03). In our experience, MACOP-B/VACOP-B appears to positively influence OS and EFS in patients affected by PMLBCL, as compared to CHOP. Consolidation IF-RT on mediastinum further improves the outcome of CR patients.

Primary mediastinal large B-cell lymphoma with sclerosis in pediatric and adolescent patients: treatment and results from three therapeutic studies of the Berlin-Frankfurt-Münster Group

PURPOSE

Primary mediastinal large B-cell lymphoma with sclerosis (PMLBL) is a rare entity of non-Hodgkin's lymphoma (NHL) arising from thymic mature B cells. Optimal treatment strategies remain to be established, especially in pediatric patients.

PATIENTS AND METHODS

This study analyzes clinical characteristics and treatment outcome of 30 pediatric patients with PMLBL, diagnosed in multicenter therapy NHL-Berlin-Frankfurt-Münster Group (BFM) trials. Treatment was stratified by stage and serum lactate dehydrogenase (LDH) and consisted of four to six 5-day courses of chemotherapy using steroids, oxazaphosphorine alkylating agents, methotrexate, cytarabine, etoposide, and doxorubicin. Radiation was not part of the protocol.

RESULTS

From April 1986 to August 1999, 1,650 patients with newly diagnosed NHL were enrolled in the NHL-BFM trials; 30 patients (1.8%) had PMLBL. Median age was 14.3 years (range, 1.4 to 16.7 years); 15 patients were male and 15 patients were female. With a median observation time of 5 years (range, 1 to 12 years), probability of event-free survival (pEFS) at 5 years was 0.70 (SE, 0.08). Two patients erroneously diagnosed as T-cell NHL received non-B-cell therapy and died from progress of disease. Events in 28 patients receiving B-cell therapy included early progress during therapy (n = 1) and relapse (n = 6). Residual mediastinal masses were present in 23 patients after two courses of therapy and in 15 patients after the end of therapy. LDH > or = 500 U/L was associated with increased risk of failure in multivariate analysis.

CONCLUSION

PMLBL mainly is found in adolescents. Dose-intense chemotherapy including high-dose methotrexate yields a pEFS at 5 years of 0.70 (SE, 0.08). LDH is of prognostic value in pediatric patients with PMLBL.

Primary mediastinal B-cell lymphoma: high frequency of BCL-6 mutations and consistent expression of the transcription factors OCT-2, BOB.1, and PU.1 in the absence of immunoglobulins

Although primary mediastinal (thymic) large B-cell lymphoma has been primarily studied, its precise phenotype, molecular characteristics, and histogenesis are still a matter of debate. The International Extranodal Lymphoma Study Group collected 137 such cases for extensive pathological review. Histologically, the lymphomatous growth was predominantly diffuse with fibrosis that induced compartmentalized cell aggregation. It consisted of large cells with varying degrees of nuclear polymorphism and clear to basophilic cytoplasm. On immunohistochemistry, the following phenotype was observed: CD45(+), CD20(+), CD79a(+), PAX5/BSAP(+), BOB.1(+), Oct-2(+), PU.1(+), Bcl-2(+), CD30(+), HLA-DR(+), MAL protein(+/-), Bcl-6(+/-), MUM1/IRF4(+/-), CD10(-/+), CD21(-), CD15(-), CD138(-), CD68(-), and CD3(-). Immunoglobulins were negative both at immunohistochemistry and in situ hybridization. Molecular analysis, performed in 45 cases, showed novel findings. More than half of the cases displayed BCL-6 gene mutations, which usually occurred along with functioning somatic IgV(H) gene mutations and Bcl-6 and/or MUM1/IRF4 expression. The present study supports the concept that a sizable fraction of cases of this lymphoma are from activated germinal center or postgerminal center cells. However, it differs from other aggressive B-cell lymphomas in that it shows defective immunoglobulin production despite the expression of OCT-2, BOB.1, and PU.1 transcription factors and the lack of IgV(H) gene crippling mutations.

Diffuse large B-cell lymphoma: one or more entities? Present controversies and possible tools for its subclassification

Diffuse large B-cell lymphoma (DLBCL) is the commonest type of lymphoid tumour world-wide. This category was included both in the REAL and WHO Classification aiming to lump together all malignant lymphomas characterized by the large size of the neoplastic cells, B-cell derivation, aggressive clinical presentation, and the need for highly effective chemotherapy regimens. These tumours are detected as primary or secondary forms both at the nodal and extranodal levels, in immunocompetent hosts as well as in patients with different types of immunosuppression. They display a significant variability in terms of cell morphology and clinical findings, which justifies the identification of variants and subtypes. Among the latter, the primary mediastinal one does actually correspond to a distinct clinicopathological entity. Immunophenotypic, tissue microarray and molecular studies underline the extreme heterogeneity of DLBCLs and suggest a subclassification of the tumour, based on the identification of different pathogenic pathways, which might have much greater relevance than pure morphology for precise prognostic previsions and adoption of ad hoc therapies. The more recent acquisitions on the pathobiology of DLBCLs are reviewed in the light of the authors' experience, aiming to contribute to the existing debate on the topic.

Mediastinal (thymic) large B-cell lymphoma: where do we stand?

Mediastinal (thymic) B-cell lymphoma (MBL) is a locally highly aggressive tumour that was first definitively described in the early 1980s. The incidence of MBL is low, which made disease characterisation difficult initially. However, MBL has several peculiar clinical, morphological, immunological, and genetic features. Collectively, these characteristics distinguish it from other diffuse, large B-cell lymphomas. Consequently, MBL has become a defined subtype of diffuse large B-cell lymphoma with its own code (9679/3) in the International Classification of Diseases. New insights into the biological and clinical aspects of MBL have been gained from the study of large numbers of cases. Nevertheless, the histogenesis of the disease is not yet fully understood. We review the available data on MBL with special emphasis on its morphological, immunological, and genetic properties. Also discussed are recent data on molecular genetics, biology, and treatment.

Hodgkin's lymphoma: the pathologist's viewpoint

Despite its well known histological and clinical features, Hodgkin's lymphoma (HL) has recently been the object of intense research activity, leading to a better understanding of its phenotype, molecular characteristics, histogenesis, and possible mechanisms of lymphomagenesis. There is complete consensus on the B cell derivation of the tumour in most cases, and on the relevance of Epstein-Barr virus infection and defective cytokinesis in at least a proportion of patients. The REAL/WHO classification recognises a basic distinction between lymphocyte predominance HL (LP-HL) and classic HL (CHL), reflecting the differences in clinical presentation and behaviour, morphology, phenotype, and molecular features. CHL has been classified into four subtypes: lymphocyte rich, nodular sclerosing, with mixed cellularity, and lymphocyte depleted. The borders between CHL and anaplastic large cell lymphoma have become sharper, whereas those between LP-HL and T cell rich B cell lymphoma remain ill defined. Treatments adjusted to the pathobiological characteristics of the tumour in at risk patients have been proposed and are on the way to being applied.

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.

Diffuse large B-cell lymphoma with primary retroperitoneal presentation: clinico-pathologic study of nine cases

Diffuse large B-cell lymphoma primarily presenting in the retroperitoneum (PRLBCL) has been the object of occasional reports, all based on dated techniques.

MATERIALS AND METHODS

Nine PRLBCLs--with clinical information and paraffin blocks available--were reviewed on morphologic, immunohistochemical and molecular grounds.

RESULTS

At microscopic examination, the cases were characterized by a diffuse proliferation of large cells (CD20+, CD79a+, CD3-), displaying a wide rim of cytoplasm (clear in seven instances and acidophilic in two), associated with sclerosis and frequent compartmentalization. Phenotypic and molecular analyses showed that: a) three cases were bcl-2+, bcl-6+, HLA-DR+, and CD10+ (1/3), with associated follicular dendritic cell (FDC) component and bcl-2 gene rearrangements; b) four cases were bcl-2, bcl-6, HLA-DR, CD10, FDC, and bcl-2 gene rearrangement negative; c) two cases had border-line characteristics (bcl-2+, bcl-6+, FDC+, HLA-DR-, CD10-, and bcl-2 gene rearrangement-). The first subgroup was thought to be of follicular derivation, as was the third due to bcl-6 and FDC stains. Of the corresponding five patients, three are in complete remission and two died of disease within 12 months. No obvious, normal counterpart was detected in the remaining four tumors: the corresponding patients died of disease in 3-23 months. The problem of similarities between PRLBCL and primary mediastinal LBCL is discussed.

CONCLUSIONS

Although the present series is small, our findings suggest that PRLBCL may represent a more heterogeneous group of tumors than previously thought, which merits further phenotypic and molecular studies to broaden the understanding of its histogenesis and behavior.

Primary mediastinal large B-cell lymphoma: a comparative study with nodular sclerosis-type Hodgkin's disease

The clinicopathological features of 10 patients with primary mediastinal large B-cell lymphoma (PMLBCL) are described. The patients were aged 19 to 63 years, with a median age of 25.5 years. There were 5 men and 5 women. All patients presented with chest symptoms, and 6 presented with superior vena cava syndrome. Nine patients had bulky mediastinal tumors. The disease was confined within the thorax and contiguous lymph nodes, although multiple liver tumors were observed in 1 patient. Laboratory findings included high lactate dehydrogenase levels and elevated C-reactive protein levels. The soluble interleukin 2-receptor level was high in 6 patients tested. A comparative study of PMLBCL and nodular sclerosis-type Hodgkin's disease (NS-HD) with a mediastinal mass revealed substantial overlap in clinical features. Histopathological examination of biopsy specimens of PMLBCL revealed clusters of CD20+ large cells; however, CD30+ Hodgkin/Reed-Sternberg-like cells were occasionally seen, raising the potential to misdiagnose PMLBCL as NS-HD. The patients with PMLBCL were treated with CHOP (cyclophosphamide, doxorubicin, vincristine, and prednisolone), biweekly CHOP, or MACOP-B (methotrexate, doxorubicin, cyclophosphamide, vincristine, prednisolone, and bleomycin) regimen, and 6 received consolidation radiotherapy to the involved field. With the exception of 1 patient who was primarily refractory to therapy, 9 patients (90%) achieved complete response and 7 (70%) remain in continuous remission with a mean follow-up of 24 months.

Alteration of chromosome arm 6p is characteristic of primary mediastinal B-cell lymphoma, as identified by genome-wide allelotyping

Five cases of primary mediastinal B-cell lymphoma (PMBL) each have been studied with 375 microsatellite markers from all 22 autosomes. Of the 151 genomic alterations among the 1,875 assays, only five were allelic losses. The remainder of the microsatellite alterations consisted of 114 allelic imbalances and 32 instabilities. Microsatellite alterations were found in all cases on chromosomal arms 6p and 9p. These allelic imbalances most likely are indicative of genetic amplification, a finding agreeing well with those of studies using either comparative genomic hybridization or arbitrarily primed polymerase chain reaction, in which amplification of chromosome arm 9p in PMBL has been found. The allelic imbalances on chromosome arm 6p always included marker D6S276 located at 6p21.3-p22.3, where the MHC class I genes reside. These allelic imbalances may be reflective of alterations in the expression of the MHC gene products, characteristic of PMBL. Allelic anomalies close to the MYB gene locus on 6q were detected in two cases and prompted the analysis of MYB rearrangements in a series of 30 lymphomas. One rearrangement was detected in one of 18 cases of PMBL and in none of 10 diffuse, large B-cell lymphomas and two T-cell lymphomas. Our genome-wide microsatellite analysis provides independent confirmation that PMBL is characterized by infrequent chromosomal losses and by frequent genetic alterations involving chromosomal arm 9p. For the first time, chromosomal arm 6p has been identified as a highly frequent target of genetic alterations in this tumor type. Finally, MYB may also be involved occasionally in PMBL pathogenesis.

Primary mediastinal B-cell lymphoma: a review of pathology and management

PURPOSE

Primary mediastinal B-cell lymphoma (PMBL) is recognized as a separate disease entity in the REAL classification. There is uncertainty about the relevance and especially the optimal management of this disorder. In this review, we discuss clinical presentation, pathology, pathobiology, and management of PMBL in order to provide a platform for initiation of further clinical and biologic studies.

MATERIALS AND METHODS

Studies were identified through a MEDLINE search and from the bibliographies of relevant articles.

RESULTS

PMBL is a tumor of young adults who present with a rapidly proliferating tumor. At diagnosis, the tumor is usually limited to intrathoracic organs. Spread to parenchymal organs such as liver, kidneys, and CNS is common at recurrence. Fibrosis and the presence of so-called clear cells are distinctive morphologic features of PMBL, although they are not pathognomonic or even necessary for diagnosis. On the other hand, biologic features relating to oncogene rearrangement and overexpression as well as cytogenetic features clearly differentiate PMBL from other types of diffuse large B-cell lymphoma. Phase II studies and retrospective series indicate cure rates that range from 38% to 88%. The role of chemotherapy, radiation, and high-dose chemotherapy with stem cell rescue in the management of PMBL is reviewed.

CONCLUSION

PMBL has unique clinical and biologic characteristics that are radically different from those of other types of diffuse large B-cell lymphoma. Although relatively rare, its aggressive growth and its occurrence in young patients increase the clinical relevance of this entity. The consistent recognition and study of PMBL will allow the development of new approaches to its management.

Large-cell lymphoma arising in the mediastinum in children and adolescents is associated with an excellent outcome: a Children's Cancer Group report

PURPOSE

Large-cell lymphoma (LCL) arising in the mediastinum (LCL-M) is a heterogeneous group of non-Hodgkin's lymphoma (NHL) that includes B-cell lymphomas as well as T-cell lymphomas, including anaplastic LCL. LCL-M is well recognized in young adults but is less well characterized and infrequent in children and adolescents.

METHODS

A retrospective review of Children's Cancer Group therapeutic studies for nonlymphoblastic lymphomas (CCG-551, CCG-503, CCG-552, and CCG-5911) identified 20 patients with LCL-M, representing 7.2% of all LCLs classified by central pathology review.

RESULTS

The patients ranged in age from 4 to 19 years (median, 12.5 years; mean, 12 years); 55% of the patients were male. Although a variety of chemotherapy regimens were used, response was excellent, with all 20 patients (100%) achieving a complete response. Four patients (20%) experienced relapse locally or in distant sites including brain and kidney. One patient died of sepsis during therapy. For the 20 patients with LCL-M, the product-limit estimated 5-year event-free survival (EFS) and 5-year overall survival (OS) rates are 75% +/- 10% and 85% +/- 8%, respectively. For disseminated LCLs (192 cases), the EFS and OS rates were 50% +/- 4% and 63% +/- 4%, respectively, which differ significantly from the those of the LCL-M cases (EFS, P =.025; OS, P =.034). The 5-year EFS and OS rates for patients with localized LCL (67 cases) were 92 +/- 3% and 97 +/- 2%, respectively.

CONCLUSION

LCL-M is a heterogeneous group of NHLs that makes up approximately 7.2% of LCL in children and adolescents. Response to therapy and OS in this young age group seems excellent and superior to that of disseminated LCLs but inferior to that of other localized LCL. Future studies of LCL-M will evaluate short intense chemotherapy administered without radiation therapy.

Treatment and Clinical Management of Primary Mediastinal Large B-Cell Lymphoma With Sclerosis: MACOP-B Regimen and Mediastinal Radiotherapy Monitored by 67Gallium Scan in 50 Patients

To evaluate the efficacy of a combined modality treatment (MACOP-B plus mediastinal radiotherapy) and the advantages of Gallium-67-citrate single-photon emission (67GaSPECT) over computed tomography (CT) for restaging in patients with primary mediastinal large B-cell lymphoma (PMLBCL) with sclerosis. Between 1989 and 1998, 50 previously untreated patients with PMLBCL with sclerosis (70% with bulky mass) were treated with MACOP-B regimen plus mediastinal radiotherapy. The radiologic clinical stage with evaluation of tumor size included CT and 67GaSPECT at diagnosis, after chemotherapy, and after radiotherapy. Forty-three patients (86%) achieved a complete response and 7 were nonresponders to treatment. For the imaging evaluation, only 47 patients were evaluable because 3 had disease progression during chemotherapy. After treatment, 3/5 (60%) patients with positive 67GaSPECT and negative CT scan relapsed, as against 0/21 (0%) with negative 67GaSPECT and CT scan. Twenty-one patients had a positive CT scan: of these, the 4 with positive 67GaSPECT all progressed, whereas there were no relapses among the 17 with negative 67GaSPECT. After radiotherapy, there was a decrease of positive CT (from 33 to 21 cases) and of positive 67GaSPECT (from 31 to 9 cases). Relapse-free survival rate was 93% at 96 months (median 39 months). In patients with PMLBCL with sclerosis, MACOP-B plus radiation therapy is a very useful first-line treatment and radiation therapy may play an important role. As regards restaging, 67GaSPECT should be considered the imaging technique of choice at least in patients who show CT positivity.

Beta-HCG aberrant expression in primary mediastinal large B-cell lymphoma

We report on a primary mediastinal large B-cell lymphoma with aberrant expression of beta-human chorionic gonadotropin (beta-hCG). The patient, a 33-year-old man, had cough, dyspnea, fever, superior vena cava syndrome, and a mediastinal bulky tumor. A biopsy showed that the latter was characterized by large cells, sclerosis, and compartmentalization. The neoplastic elements expressed CD45, CD20, CD79a and, partially, CD30, whereas they were negative for CD3, epithelial membrane antigen and cytokeratins. Surprisingly, they displayed a clear-cut positivity for beta-hCG. The remaining oncofetal markers applied (PLAP and alpha1-fetoprotein) were negative. Electron microscopy demonstrated the presence of numerous nuclear pockets and the lack of intercellular junctions. DNA analysis by polymerase chain reaction showed clonal rearrangement of Ig heavy-chain genes. The patient responded promptly to the administration of MACOP-B. To the best of our knowledge, this is the first example of B-cell lymphoma showing positivity for beta-hCG; a similar aberrant expression was previously observed only in three Japanese patients with human T-cell lymphotropic virus type I+ adult T-cell lymphoma/leukemia. Because primary mediastinal large B-cell lymphoma has in the past been frequently confused with germ cell tumors, pathologists should be aware of possible beta-hCG expression by lymphomatous cells to avoid the risk of misdiagnosis.

Primary mediastinal large B-cell lymphoma: a clinicopathologic study of 43 patients from the Nebraska Lymphoma Study Group

PURPOSE

To investigate whether primary mediastinal large B-cell lymphoma (PMLBL) is a distinct clinicopathologic entity with a more aggressive course than other diffuse large B-cell lymphomas (DLBL).

MATERIALS AND METHODS

All patients with CD20-positive DLBL who presented with a mediastinal mass measuring at least 5.0 cm and were treated with curative intent were identified. A control group of 352 patients with nonmediastinal DLBL was selected for comparison.

RESULTS

The 43 patients with PMLBL had a male to female ratio of 20:23 and a median age of 42 years. Stage I/II disease was present in 58% of the patients, with only 9% having bone marrow involvement. A complete remission was achieved in 63% of the patients, and the 5-year overall and failure-free survivals were 46% and 38%, respectively. Among the clinical variables, an elevated serum lactate dehydrogenase level, a low performance score, more than one extranodal site, and an intermediate or high International Prognostic Index score were predictive of poor survival. When compared with the DLBL group, a younger median age was the only clinical feature that was significantly different in the PMLBL group.

CONCLUSION

The clinical features of PMLBL do not appear to be significantly different from those of nonmediastinal DLBL. Although the younger age of onset, slight female predominance, mediastinal location, and size of the mass may justify the recognition of PMLBL as a clinical syndrome, additional evidence is needed to define it as a distinct disease entity.

Mediastinal B-cell lymphoma: a study of its histomorphologic spectrum based on 109 cases

Mediastinal B-cell lymphoma (MBL) is a distinct variant of aggressive non-Hodgkin's lymphoma with characteristic clinical and biological features but less well-defined histomorphology. We reevaluated 124 biopsy specimens from 109 MBL patients of an Italian/French/German retrospective clinical study. MBL was primarily diagnosed on clinical and histological grounds in conjunction with the detection of CD20 expression by immunohistology. Cytologically, MBL features limited intralesional but considerable interindividual cytological diversity, ranging from medium-sized to very large, atypical cells. Sclerosis and necrosis are restricted to extrathymic and extranodal sites of involvement, predominantly the lung, as is angioinvasion, which predominantly affects larger vessels. The medium-sized and the large cell variants resemble marginal zone lymphoma variants, whereas the very large cell variant of MBL has not so far been found to have any extramediastinal counterpart. We conclude that MBL displays a broad morphological spectrum covering more than is implied by the term "diffuse large cell lymphoma." Because statistical analysis of cytological and histological criteria failed to correlate with prognosis in this comprehensive group of patients, we think it inadvisable further to subclassify MBL.

Evaluation and management of the "new" lymphoma entities: mantle cell lymphoma, lymphoma of mucosa-associated lymphoid tissue, anaplastic large-cell lymphoma, and primary mediastinal B-cell lymphoma

Non-Hodgkin's lymphomas (NHL) represent a major health problem worldwide, and incidence has been on the rise continuously for the last few decades. It is estimated that approximately 55,000 new cases of NHL will be diagnosed in the United States in 1998 and that slightly fewer than 25,000 patients will die of treatment failure or recurrent disease. The rising incidence of NHL is related not only to the acquired immunodeficiency syndrome epidemic but to also a steady increase in the number of cases diagnosed in older patients without immunosuppression. The new pathologic classification of NHL (revised European-American lymphoma classification, REAL) developed by the International Lymphoma Study Group (ILSG) is already resulting in more accurate disease-specific epidemiologic and clinical investigations. These studies have brought a new awareness of the existence and the relative prevalence of discrete NHL subtypes that appear to predominate among patients in different populations according to age, sex, geographic distribution, and predisposing conditions. This developing database has also the potential to result in the discovery of specific environmental causes, predisposing genetic factors, and therapeutic approaches. Some of the entities defined in the REAL classification, such as follicular lymphomas, diffuse B large-cell lymphomas, and T-cell lymphoblastic lymphomas, were already well described in the older classification systems (Kiel and Working Formulation). Others, such as mantle cell lymphoma, (MCL) anaplastic large-cell lymphoma (ALCL), lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma), and primary mediastinal B-cell lymphoma (PMBCL) are relatively new members of the family, and accurate data on their clinicopathologic features and natural histories have only recently begun to emerge. This review presents in detail the most recent data on the clinical presentation of, diagnostic evaluation of, and treatment options for the most common of the new NHL entities: MCL, MALT lymphoma, CD30+ (Ki-1+) ALCL, and PMBCL. These four entities combined represent approximately 20% of all cases of NHL and exemplify well the broad clinicopathologic spectrum of NHL and the diagnostic and therapeutic challenges facing those who care for patients affected by these conditions.

MACOP-B and involved field radiation therapy is an effective therapy for primary mediastinal large B-cell lymphoma with sclerosis

PURPOSE

To evaluate the clinical features of presentation and the response to two different third-generation regimens (F-MACHOP and MACOP-B) of primary mediastinal large B-cell lymphoma (MLBCL), a recently defined distinct clinicopathological entity of non-Hodgkin's lymphoma (NHL).

PATIENTS AND METHODS

Thirty-seven consecutive patients with MLBCL, eight male and 29 female (F/M ratio 1:3.5) with a median age of 35 years, were enrolled in the present study. Thirty-five (94.5%) patients presented disease confined to thorax, with chest symptoms of a rapidly enlarging mass in the mediastinum in 70% and superior vena cava syndrome (SCVS) in 43% of these patients. The first 10 patients received F-MACHOP and the succeeding 27 patients MACOP-B chemotherapy, associated in 24 (88.8%) with involved field radiation therapy (IFRT). 67Gallium scan was routinely performed pre- and post-IFRT in 18 patients.

RESULTS

All 37 patients were assessable for response: 10 of 10 (100%) in the F-MACHOP and 26 of 27 (96.3%) in the MACOP-B group achieved overall responses (CR + PR). Three of 24 (12.5%) patients in PR after chemotherapy obtained CR after IFRT. Persistent Gallium avidity was observed in 16 patients after chemotherapy and in only four patients after IFRT. Thus far, four of the 10 F-MACHOP and two of the 26 MACOP-B responders have presented disease progression. The probability of progression-free survival (PFS) was 91% and 60% (P < 0.02) while overall survival (OS) was 93% and 70% (P = n.s.) at a mean follow-up of 27 and 52 months in the MACOP-B + IFRT and F-MACHOP groups, respectively.

CONCLUSION

MACOP-B + IFRT has proved to be a highly effective and less toxic therapeutic approach for primary MLBCL and appears to be superior to other third-generation chemotherapy regimens.

Primary mediastinal B-cell lymphoma: update of its clinicopathologic features

The peculiar clinical, histomorphological and biological characteristics of PMBCL are reviewed. Special emphasis is given to the frequent aggressive clinical behaviour of this lymphoma in which conventional prognostic factors seem inadequate to identify high risk cases. The need for new clinical and/or biological prognostic markers is stressed.

Results of High-Dose Therapy and Autologous Bone Marrow/Stem Cell Transplantation During Remission in Poor-Risk Intermediate- and High-Grade Lymphoma: International Index High and High-Intermediate Risk Group

We have conducted a pilot study to investigate the role of high-dose therapy and autologous bone marrow/stem cell transplantation (ASCT) during first complete or partial remission in 52 patients with poor-risk aggressive lymphoma. There were 42 patients with intermediate-grade or immunoblastic lymphoma who were considered to be high (60%) and high-intermediate risk (40%) groups at diagnosis based on the age-adjusted International Prognostic Index (IPI) and 10 patients with high-grade, SNCCL (small non-cleaved cell, Burkitt's, and non-Burkitt's), who at presentation had poor-risk features defined as elevated serum lactate dehydrogenase level, stage IV, and bulky mass ≥10 cm. The median age was 34 years (range, 16 to 56 years). Thirty-nine were transplanted in first complete remission and 13 in first partial remission after conventional therapy. Conditioning regimens consisted of total body irradiation (TBI) administered as a single fraction 750 cGy in 3 patients and in fractionated doses for a total of 1,200 cGy in 44 patients, in combination with 60 mg/kg etoposide and 100 mg/kg cyclophosphamide. Five patients with prior radiotherapy received 450 mg/m2 carmustine instead of TBI. Stem cell sources were either bone marrow and/or peripheral blood. No in vitro purging was used. All patients engrafted. Two SNCCL patients died of venoocclusive disease at 25 days and acute leukemia at 27 months posttransplantation. There were six relapses at 1.5 to 12.8 months posttransplantation. At a median follow-up of 44 months (range, 1 to 113 months), the estimated 3-year overall survival (OS) and disease-free survival (DFS) for all patients was 84% (95% confidence interval [CI], 70% to 92%) and 82% (95% CI, 68% to 91%), respectively. In the subset of patients with intermediate-grade and immunoblastic lymphoma, the 3-year DFS was 89% (95% CI, 74% to 96%) for all patients, 87% (95% CI, 67% to 96%) for high-risk patients, and 92% (95 CI, 61% to 99%) for high-intermediate risk patients. The 3-year OS and DFS for SNCCL patients were identical at 60% (95% CI, 30% to 84%). These results suggest that high-dose therapy and ASCT during first remission may improve the survival and prognosis of patients with poor-risk intermediate- and high-grade lymphoma. A prospective randomized study comparing high-dose therapy and ASCT with conventional chemotherapy in IPI high-risk patients with aggressive non-Hodgkin's lymphoma should be undertaken.

Primary Mediastinal B-cell lymphoma with sclerosis: clinical and therapeutic evaluation of 22 patients

In the last decade, there have been several reports on what is now recognized as a new clinical and pathological entity termed primarily mediastinal B-cell lymphoma (PMBCL) with sclerosis. This lymphoma presents unique clinical characteristics with an aggressive outcome and, at present, the best approach seems to be a combination of chemotherapy and radiotherapy. Between June 1989 and September 1994, twenty-two previously untreated patients with PMBCL with sclerosis were treated with a combination of third-generation chemotherapy regimen (MACOP-B or F-MACHOP) and mediastinal irradiation. All the patients presented with bulky mediastinal involvement; the radiologic clinical stage with evaluation of tumor size included computed tomography and Gallium-67-citrate SPECT. Twenty-one patients (95%) achieved a complete response and only one was resistant to treatment. Regarding 67Ga SPECT, 6 patients, including the nonresponder, showed persistent abnormal 67Ga uptake after chemotherapy; however after the mediastinal radiotherapy, all the patients except for the nonresponder were 67Ga-negative. The overall survival was 87%, with a median follow-up of 24 months from the time of diagnosis. Two of the patients who achieved complete response relapsed 7 and 10 months after completion of treatment, respectively. The relapse-free survival rate was 89% at 62 months (median 20 months). In patients presenting with bulky mediastinal PMBCL with sclerosis combined modality treatment using third-generation chemotherapy regimens and radiotherapy induces a good remission rate with greater than 80% chance of surviving disease-free, at 2 years. A longer follow-up before definitive conclusions are drawn is still warranted.