Primary testicular diffuse large B-cell lymphomas have activated B-cell-like subtype characteristics

IELSG30 phase 2 trial: intravenous and intrathecal CNS prophylaxis in primary testicular diffuse large B-cell lymphoma

ABSTRACT

Primary testicular diffuse large B-cell lymphoma (PTL) is characterized by high risk of contralateral testis and central nervous system (CNS) relapse. Chemoimmunotherapy with intrathecal (IT) CNS prophylaxis and contralateral testis irradiation eliminates contralateral recurrences and reduces CNS relapses. The IELSG30 phase 2 study investigated feasibility and activity of an intensified IT and IV CNS prophylaxis. Patients with stage I/II PTL who had not received treatment received 2 cycles of IV high-dose methotrexate (MTX) (1.5 g/m2) after 6 cycles of the R-CHOP regimen (rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone, every 21 days). IT liposomal cytarabine was administered on day 0 of cycles 2 to 5 of 21-day R-CHOP regimen. Contralateral testis radiotherapy (25-30 Gy) was recommended. Fifty-four patients (median age: 66 years) with stage I (n = 32) or II (n = 22) disease were treated with R-CHOP, 53 received at least 3 doses of IT cytarabine, 48 received at least 1 dose of IV MTX, and 50 received prophylactic radiotherapy. No unexpected toxicity occurred. At a median follow-up of 6 years, there was no CNS relapse; 7 patients progressed, and 8 died, with 5-year progression-free and overall survival rates of 91% (95% confidence interval [CI], 79-96) and 92% (95% CI, 81-97), respectively. Extranodal recurrence was documented in 6 patients (in 2 without nodal involvement). In 4 cases, the relapse occurred >6 years after treatment. Causes of death were lymphoma (n = 4), second primary malignancy (n = 1), cerebral vasculopathy (n = 1), unknown (n = 2). Intensive prophylaxis was feasible and effective in preventing CNS relapses. Late relapses, mainly at extranodal sites, represented the most relevant pattern of failure. This trial was registered at www.clinicaltrials.gov as #NCT00945724.

Recent updates on central nervous system prophylaxis in patients with high-risk diffuse large B-cell lymphoma

The use of central nervous system (CNS) prophylaxis for patients with diffuse large B-cell lymphoma (DLBCL) remains controversial. Although uncommon, CNS relapses are invariably fatal in this otherwise curable disease. Accurate identification of patients at risk and the optimal approach to CNS prophylaxis therefore remains an area of unmet need. The existing literature, largely retrospective in nature, provides mixed conclusions regarding the efficacy of CNS prophylaxis. The utility of CNS prophylaxis has itself been challenged. In this review, we dissect the issues which render the value of CNS prophylaxis uncertain. We first compare international clinical guidelines for CNS prophylaxis. We then interrogate the factors that should be used to identify high-risk patients accurately. We also explore how clinical patterns of CNS relapse have changed in the pre-rituximab and rituximab era. We then discuss the efficacy of CNS-directed approaches, intensification of systemic treatment and other novel approaches in CNS prophylaxis. Improved diagnostics for early detection of CNS relapses and newer therapeutics for CNS prophylaxis are areas of active investigation. In an area where prospective, randomized studies are impracticable and lacking, guidance for the use of CNS prophylaxis will depend on rigorous statistical review of retrospective data.

[Lymphomas and other hematological neoplasms in the testicles]

BACKGROUND

The testis may be infiltrated by hematological neoplasias. However, only few entities present as primary testicular diseases.

OBJECTIVES

To present hematological neoplasias in the testis, especially primary testicular hematological diseases.

MATERIALS AND METHODS

Selective literature research ( http://www.ncbi.nlm.nih.gov ) was combined with the clinico-pathological experience of the authors.

RESULTS

We present the experience of the lymph node registry Kiel with hematological neoplasias of the testis and develop a staining recommendation. According to our data, the testis is mainly involved by diffuse large B‑cell lymphomas (~70% of cases) followed by precursor cell neoplasias (~20%). Most precursor cell neoplasias are disseminated diseases involving the testis. Primary testicular lymphomas are nearly exclusively diffuse large B‑cell lymphomas that show specific clinical, pathological, and molecular features discriminating them from nodal/disseminated lymphomas. Primary testicular follicular lymphomas, which have been described in the literature, seem to be extremely rare.

CONCLUSION

Primary testicular lymphomas are predominantly diffuse large B‑cell lymphomas. The diagnosis is possible with few immunohistochemical stainings. However, histology cannot replace clinical staging to discriminate primary testicular lymphoma from secondary infiltration by a nodal/disseminated disease.

Testicular Diffuse Large B-Cell Lymphoma-Clinical, Molecular, and Immunological Features

Simple Summary

Testicular diffuse large B-cell lymphoma (T-DLBCL) is a rare and aggressive lymphoma entity that mainly affects elderly men. It has a high relapse rate with especially the relapses of the central nervous system associating with dismal outcome. T-DLBCL has a unique biology with distinct genetic characteristics and clinical presentation, and the increasing knowledge on the tumor microenvironment of T-DLBCL highlights the significance of the host immunity and immune escape in this rare lymphoma, presenting in an immune-privileged site of the testis. This review provides an update on the latest progress made in T-DLBCL research and summarizes the clinical perspectives in T-DLBCL.

Abstract

Primary testicular lymphoma is a rare lymphoma entity, yet it is the most common testicular malignancy among elderly men. The majority of the cases represent non-germinal center B-cell-like (non-GCB) diffuse large B-cell lymphoma (DLBCL) with aggressive clinical behavior and a relatively high relapse rate. Due to the rareness of the disease, no randomized clinical trials have been conducted and the currently recognized standard of care is based on retrospective analyses and few phase II trials. During recent years, the tumor microenvironment (TME) and tumor-related immunity have been the focus of many tumor biology studies, and the emergence of targeted therapies and checkpoint inhibitors has significantly modulated the field of cancer therapies. Testicular DLBCL (T-DLBCL) is presented in an immune-privileged site of the testis, and the roles of NF-κB pathway signaling, 9p24.1 aberrations, and tumor-infiltrating immune cells, especially immune checkpoint expressing lymphocytes and macrophages, seem to be unique compared to other lymphoma entities. Preliminary data on the use of immune checkpoint inhibitors in the treatment of T-DLBCL are promising and more studies are ongoing.

Metachronous extranodal natural killer/T-cell lymphoma of nasal type and primary testicular lymphoma

We report a rare case of metachronous lymphoma with two distinct cell lineages in a 75-year-old man. The patient complained about having nasal obstruction for 2 years and extranodal natural killer (NK)/T-cell lymphoma of the nasal type was diagnosed from a biopsy. The immunohistochemical staining for CD56 and in situ hybridization for Epstein-Barr virus (EBV)-encoded small RNA (EBER-ISH) were positive and the tumor cells were negative for CD20. After 13 months of concurrent chemoradiotherapy, the patient presented with swelling of the left testis. Positron emission tomography scan detected an abnormal uptake in the testis. A diffuse large B-cell lymphoma, not otherwise specified, was diagnosed from subsequent radical orchiectomy. The immunohistochemical staining revealed to be positive for CD20, BCL2, BCL6, and MYC and negative for CD10 and EBER-ISH.

Lymphomas arising in immune-privileged sites: insights into biology, diagnosis, and pathogenesis

Session 2 of the 2018 European Association of Hematopathology/Society for Hematopathology Workshop focused on lymphomas arising in immune-privileged sites: both lymphomas arising in the traditionally described "immune sanctuary" sites of the central nervous system (CNS) and testes, as well as those arising at sites of local immune privilege. Primary CNS large B cell lymphoma and primary testicular large B cell lymphoma were discussed, and the biology of these unique tumors was highlighted by several cases showing the classic mutation profile including MYD88 L265P and CD79B. The tendency of these tumors to involve both the CNS and testis was also reinforced by several cases. Four cases of low-grade B cell lymphomas (LGBCL) of the CNS were discussed. Two were classic Bing-Neel syndrome associated with LPL, and two were LGBCL with plasmacytic differentiation and amyloid deposition without systemic disease. Rare examples of systemic T and NK cell lymphomas involving the CNS were also discussed. Several cases of breast implant-associated anaplastic large cell lymphoma (BI-ALCL) were submitted showing the typical clinicopathologic features. These cases were discussed along with a case with analogous features arising in a patient with a gastric band implant, as well as large B cell lymphomas arising alongside foreign materials. Finally, large B cell lymphomas arising in effusions or localized sites of chronic inflammation (fibrin-associated diffuse large B cell lymphoma [DLBCL] and DLBCL associated with chronic inflammation) were described. The pathogenesis of all of these lymphomas is believed to be related to decreased immune surveillance, either innate to the physiology of the organ or acquired at a local site.

Excellent outcomes and lack of prognostic impact of cell of origin for localized diffuse large B-cell lymphoma in the rituximab era

Therapeutic options for limited-stage diffuse large B cell lymphoma (DLBCL) include short- or full-course R-CHOP (rituximab, cyclophosphamide, doxorubicin, vincristine, prednisolone) ± radiotherapy. The optimal treatment remains unclear. The prognostic value of cell-of-origin (COO) in early stage DLBCL is unknown. Patients with limited-stage DLBCL (stage I or stage II, non-bulky) treated with R-CHOP ± involved field radiotherapy (IFRT) from 1999 to 2012 were included. COO by the Hans algorithm was analysed in a subset of patients. Of 261 patients, 30% were stage I (N = 82), 37% stage IE (N = 96), <1% stage IXEE (N = 1), 18% stage II (N = 46) and 14% stage IIE (N = 37). The stage-modified International Prognostic Index stratified patients into prognostically relevant groups. There was no significant difference in progression-free survival (PFS) or overall survival (OS) for patients in the germinal centre B-cell-like (GCB; n = 65) and non-GCB cohorts (n = 22). Seventeen patients received R-CHOP × 3-4 cycles (Arm A), 147 received R-CHOP × 3-4 cycles + IFRT (Arm B), 48 received R-CHOP × 6 cycles (Arm C), and 50 received R-CHOP × 6 cycles + IFRT (Arm D). The outcomes were excellent, with 5-year PFS of 82% and 5-year OS of 93%, and were similar across the 4 treatment groups. In the rituximab era, outcomes for limited-stage DLBCL, regardless of treatment approach, were excellent. Baseline COO was not a significant prognostic factor in patients treated with short-course R-CHOP + IFRT.

High prevalence of the MYD88 mutation in testicular lymphoma: Immunohistochemical and genetic analyses

The activating mutation of MYD88 has been identified in diffuse large B-cell lymphoma (DLBCL). We investigated the mutational status and both the gene amplification and protein expression of MYD88 in 23 cases of testicular DLBCL. To detect the MYD88 mutations, we employed the allele-specific PCR and Sanger sequencing. MYD88 gene amplification and protein expression were analyzed by quantitative PCR and by immunohistochemistry, respectively. There were 17 cases of primary testicular DLBCL: 94% (16/17) exhibited a non-Germinal center B-cell (non-GCB) subtype, 82% (14/17) showed the MYD88 L265P, and 65% (11/17) had intense expression of MYD88. When compared with normal lymph nodes, the MYD88 is significantly amplified in primary testicular DLBCL. However, the amplification status showed no correlation with its mutational status or protein expression. Moreover, neither the MYD88 mutational status nor the expression pattern affected overall survival. Six cases were secondary testicular DLBCL with an 83% (5/6) and an 80% (4/5) incidence of the non-GCB subtype and of the MYD88 L265P, respectively. In conclusion, we demonstrated a high prevalence of the non-GCB subtype and the common MYD88 L265P in both primary and secondary testicular DLBCL. Our data suggest that the MYD88 mutation is a fairly consistent genetic feature in testicular DLBCL.

Treatment of primary testicular diffuse large B cell lymphoma without prophylactic intrathecal chemotherapy: a single center experience

Background

Primary testicular diffuse large B-cell lymphoma (DLBCL) is a rare but aggressive extranodal lymphoma, and its relapse in the central nervous system (CNS) is a major concern during treatment. Despite this, the role of intrathecal prophylaxis in primary testicular DLBCL remains controversial.

Methods

We retrospectively reviewed the medical records of 14 patients with primary testicular DLBCL diagnosed between November 2000 and June 2012, and analyzed the CNS relapse rate in patients treated without intrathecal prophylaxis. Survival curves were estimated using the Kaplan-Meier method.

Results

The median age at diagnosis was 57 years (range, 41-79 years). Unilateral testicular involvement was observed in 13 patients. Nine patients had stage I, 1 had stage II, and 4 had stage IV disease. The international prognostic index was low or low-intermediate risk in 12 patients and high-intermediate risk in 2 patients. Thirteen patients underwent orchiectomy. All the patients received systemic chemotherapy without intrathecal prophylaxis, and prophylactic radiotherapy was administered to the contralateral testis in 12 patients. The median follow-up period of surviving patients was 39 months (range, 10-139 months). Median overall survival was not reached and the median progression-free survival was 3.8 years. Four patients experienced relapse, but CNS relapse was observed in only one patient (7.1%) with stage IV disease, 27 months after a complete response.

Conclusion

Even without intrathecal prophylaxis, the rate of relapse in the CNS was lower in the Korean patients with primary testicular DLBCL compared to prior reports.

Primary testicular lymphoma

Primary testicular lymphoma (PTL) is a rare, clinically aggressive form of extranodal lymphoma. The vast majority of cases are histologically diffuse large B-cell lymphoma, but rarer subtypes are clinically important and must be recognized. In this review, we discuss the incidence, clinical presentation, and prognostic factors of PTL and present a summary of the recent advances in our understanding of its pathophysiology, which may account for the characteristic clinical features. Although outcomes for patients with PTL have historically been poor, significant gains have been made with the successive addition of radiotherapy (RT), full-course anthracycline-based chemotherapy, rituximab and central nervous system–directed prophylaxis. We describe the larger retrospective series and prospective clinical trials and critically examine the role of RT. Although rituximab plus cyclophosphamide, doxorubicin, vincristine, and prednisone given every 21 days with intrathecal methotrexate and locoregional RT is the current international standard of care, a substantial minority of patients progress, representing an unmet medical need. Finally, we discuss new treatment approaches and recent discoveries that may translate into improved outcomes for patients with PTL.

High prevalence of oncogenic MYD88 and CD79B mutations in diffuse large B-cell lymphomas presenting at immune-privileged sites

Activating mutations in CD79 and MYD88 have recently been found in a subset of diffuse large B-cell lymphoma (DLBCL), identifying B-cell receptor and MYD88 signalling as potential therapeutic targets for personalized treatment. Here, we report the prevalence of CD79B and MYD88 mutations and their relation to established clinical, phenotypic and molecular parameters in a large panel of DLBCLs. We show that these mutations often coexist and demonstrate that their presence is almost mutually exclusive with translocations of BCL2, BCL6 and cMYC, or Epstein–Bar virus infection. Intriguingly, MYD88 mutations were by far most prevalent in immune-privileged site-associated DLBCL (IP-DLBCL), presenting in central nervous system (75%) or testis (71%) and relatively uncommon in nodal (17%) and gastrointestinal tract lymphomas (11%). Our results suggest that MYD88 and CD79B mutations are important drivers of IP-DLBCLs and endow lymphoma-initiating cells with tissue-specific homing properties or a growth advantage in these barrier-protected tissues.

Primary testicular lymphoma

Primary testicular non-Hodgkin lymphoma (PTL) comprises around 9% of testicular cancers and 1-2% of all non-Hodgkin lymphomas. Its incidence is increasing and it primarily affects older men, with a median age at presentation of around 67 years. By far the most common histological subtype is diffuse large B-cell lymphoma, accounting for 80-90% of PTLs. Most patients present with a unilateral testicular mass or swelling. Up to 90% of patients have stage I or II disease at diagnosis (60 and 30%, respectively) and bilateral testicular involvement is seen in around 35% of patients. PTL demonstrates a continuous pattern of relapse and propensity for extra-nodal sites such as the central nervous system and contralateral testis. Retrospective data have emphasised the importance of prophylactic radiotherapy in reducing recurrence rates within the contralateral testis. Recent outcome data from the prospective IELSG-10 trial have shown far better progression-free and overall survival than historical outcomes. This supports the use of orchidectomy followed by Rituximab- cyclophosphamide, doxorubicin, vincristine and prednisolone (R-CHOP), central nervous system prophylaxis and prophylactic radiotherapy to the contralateral testis with or without nodal radiotherapy in patients with limited disease. Central nervous system relapse remains a significant issue and future research should focus on identifying the best strategy to reduce its occurrence. Here we discuss the evidence supporting combination chemotherapy and radiotherapy in PTL.

Partial plasma cell differentiation as a mechanism of lost major histocompatibility complex class II expression in diffuse large B-cell lymphoma

Loss of major histocompatibility complex class II (MHC II) expression is associated with poor patient outcome in diffuse large B-cell lymphoma (DLBCL). As MHC II molecules are lost with plasmacytic differentiation in normal cells, we asked whether MHC II loss in DLBCL is associated with an altered differentiation state. We used gene expression profiling, quantum dots, and immunohistochemistry to study the relationship between MHC II and plasma cell markers in DLBCL and plasmablastic lymphoma (PBL). Results demonstrate that MHC II(-) DLBCL immunophenotypically overlap with PBL and demonstrate an inverse correlation between MHC II and plasma cell markers MUM1, PRDM1/Blimp1, and XBP1s. In addition, MHC II expression is significantly higher in germinal center-DLBCL than activated B cell-DLBCL. A minor subset of cases with an unusual pattern of mislocalized punctate MHC II staining and intermediate levels of mRNA is also described. Finally, we show that PBL is negative for MHC II. The results imply a spectrum of MHC II expression that is more frequently diminished in tumors derived from B cells at the later stages of differentiation (with complete loss in PBL). Our observations provide a possible unifying concept that may contribute to the poor outcome reported in all MHC II(-) B-cell tumors.

First-Line Treatment for Primary Testicular Diffuse Large B-Cell Lymphoma With Rituximab-CHOP, CNS Prophylaxis, and Contralateral Testis Irradiation: Final Results of an International Phase II Trial

Purpose

Primary testicular lymphoma (PTL) has poor prognosis with failures in contralateral testis, CNS, and extranodal sites. To prevent these events, we designed an international phase II trial (International Extranodal Lymphoma Study Group 10 [IELSG-10]) that addressed feasibility and activity of conventional chemoimmunotherapy associated with CNS prophylaxis and contralateral testis irradiation. The trial was conducted by the IELSG and the Italian Lymphoma Foundation.

Patients and Methods

Fifty-three patients (age 22 to 79 years) with untreated stage I or II PTL were treated with six to eight courses of rituximab added to cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP) every 21 days (R-CHOP21); four doses of intrathecal methotrexate (IT-MTX) and radiotherapy (RT) to the contralateral testis (30 Gy) for all patients and to regional lymph nodes (30 to 36 Gy) for stage II disease.

Results

All patients received R-CHOP21, 50 received CNS prophylaxis, and 47 received testicular RT. With a median follow-up of 65 months, 5-year progression-free survival and overall survival rates were 74% (95% CI, 59% to 84%) and 85% (95% CI, 71% to 92%), respectively. Ten patients relapsed or progressed: two in lymph nodes, five in extranodal organs, and three in the CNS. The 5-year cumulative incidence of CNS relapse was 6% (95% CI, 0% to 12%). No contralateral testis relapses occurred. Ten patients died: lymphoma (n = 6), secondary leukemia (n = 2), heart failure (n = 1), and gastric cancer (n = 1). Grade 3 to 4 toxicities were neutropenia, 28%; infections, 4%; and neurologic, 13%. No deaths occurred as a result of toxicity.

Conclusion

This international prospective trial shows that combined treatment with R-CHOP21, IT-MTX, and testicular RT was associated with a good outcome in patients with PTL. RT avoided contralateral testis relapses, but CNS prophylaxis deserves further investigation.

The isotype of the BCR as a surrogate for the GCB and ABC molecular subtypes in diffuse large B-cell lymphoma

Gene expression profiling has identified two major molecular subtypes of diffuse large B-cell lymphoma (DLBCL) that are histologically indistinguishable but differ in cure rates. Here, we investigated whether the isotype of the B-cell receptor (BCR) expressed by the tumoral cells correlated with the molecular subtype and survival. Gene expression analysis clustered the 53 patients included in this study into three subgroups, 17 germinal center B-cell-like (GCB) cases, 26 activated B-cell-like (ABC) cases and 10 intermediate cases. The molecular subtype was correlated with the isotype, as 15/17 GCB cases expressed a secondary isotype (immunoglobulin (Ig)G or IgA), whereas 24/26 ABC cases expressed a primary isotype (IgM or IgD) (P<0.0001). There was a trend toward a worse outcome for patients with an ABC DLBCL and a shorter overall survival for patients with IgM+ tumor (P=0.21 and 0.014, respectively). Finally, fluorescence in situ hybridization (FISH) analysis revealed a striking asymmetric pattern, as the IGHM gene is conserved only on the productive IGH allele in most IgM+ tumors. Taken together, these data indicate that the isotype of the BCR is a reliable indicator for the GCB and ABC subtypes in DLBCL, and suggest that the conservation of an IgM is required for ABC DLBCL lymphomagenesis to occur.

The molecular background of aggressive B cell lymphomas as a basis for targeted therapy

In contrast to classifications for the majority of solid tumours, non-Hodgkin's lymphomas have been defined on the basis of their genetic alterations for many years, providing a biologically highly relevant classification. However, for aggressive B cell lymphomas, which unfortunately is the most prevalent group of lymphomas in adults, the stratification is less optimal. Gene expression profiling, analyses of chromosomal alterations and functional assays have been instrumental in dissecting these tumours to support the distinction of essentially different diseases, such as diffuse large B cell lymphoma and Burkitt's lymphoma, and now start to identify the dominant driving oncogenetic pathways that may serve as rational therapeutic targets in this essentially heterogeneous group. In this review, the molecular background and the consequences of the molecular alterations in the context of the consequences for treatment in aggressive B cell lymphoma are discussed.

Primary testicular diffuse large B-cell lymphoma shows an activated B-cell-like phenotype

The most common type of primary testicular lymphoma is diffuse large B-cell type, which has a poor prognosis relative to other extra-nodal diffuse large B-cell lymphomas (DLBCL). These constitute a heterogeneous group of lymphomas with germinal center B-cell-like and activated B-cell-like subtypes. Such a distinction theoretically utilizes the immunohistochemical expression of CD10, Bcl-6, and MUM1. The purpose of this study was that we could stratify primary testicular lymphoma of diffuse large B-cell type according to this scheme, and further elucidate the reason why primary testicular diffuse large B-cell lymphoma possesses a poor clinical outcome. Seventeen Chinese patients with primary testicular DLBCL were examined by means of a 3-antibody panel (CD10, Bcl-6, MUM1). Among these 17 cases, 16 were assigned to the activated B-cell-like subtypes. One case was classified as germinal center B-cell-like type. Twelve of these 17 cases expressed high proliferative activity (>or=40% Ki-67 labeling). The majority of primary testicular DLBCLs have activated B-cell-like subtype characteristics and high proliferative activity. These features might be a significant factor; moreover, they are associated with poor prognosis.

Low levels of monoclonal small B cells in the bone marrow of patients with diffuse large B-cell lymphoma of activated B-cell type but not of germinal center B-cell type

BACKGROUND

Multiparameter flow cytometry allows the detection of minor monoclonal B-cell populations. Using this technique combined with morphology, we were struck by the presence of minor populations of small monoclonal B cells in bone marrows of patients with diffuse large B-cell lymphoma in routine diagnostic samples and performed a systematic retrospective study.

DESIGN AND METHODS

Bone marrows of 165 patients with primary diffuse large B-cell lymphoma without histological evidence of concurrent non-Hodgkin's lymphoma were studied by routine microscopy of trephines and smears, immunohistochemistry and multiparameter flow cytometry.

RESULTS

Diffuse large B-cell lymphoma infiltration in marrows was documented in 11 of 165 patients. Morphological examination consistently revealed a higher tumor load than evidenced by flow cytometry. Of interest, only 3 of 119 patients with diffuse large B-cell lymphoma not otherwise specified, the largest subtype, showed marrow infiltration. By contrast, flow cytometry revealed a minor monoclonal B-cell population in 24 of 165 patients, none of whom showed diffuse large B-cell lymphoma infiltration by morphology. Of interest, morphological examination revealed the presence of small B cells in the marrows of those patients. Moreover, 11 of 39 (28.2%) of patients with diffuse large B-cell lymphoma not otherwise specified of ABC subtype and only 3 of 80 (3.7%) with the GCB subtype showed these monoclonal small B cells (P=0.0002). In addition 4 of 8 (50%), 4 of 15 (26.7%) and 2 of 3 (66.7%) patients with primary testicular, primary central nervous system and leg-type diffuse large B-cell lymphoma, respectively, showed monoclonal small B cells.

CONCLUSIONS

Bone marrow infiltration with diffuse large B-cell lymphoma in patients with diffuse large B-cell lymphoma not otherwise specified is rare at diagnosis. By contrast, a high number of diffuse large B-cell lymphoma not otherwise specified of the ABC subtype but not of GCB subtype is associated with monoclonal small B cells in the marrow. Whether these monoclonal small B cells are precursors of diffuse large B-cell lymphoma of the ABC type or arise in a common background that favors clonal B-cell expansion remains to be demonstrated.

Specific expression of miR-17-5p and miR-127 in testicular and central nervous system diffuse large B-cell lymphoma

Recent studies have shown that certain non-coding short RNAs, called miRNAs, play an important role in diffuse large B-cell lymphomas. Patients with diffuse large B-cell lymphoma have great diversity in both clinical characteristics, site of presentation and outcome. The aim of our study is to validate the differential expression in germinal center and non-germinal center diffuse large B-cell lymphoma,s and to study to the extent to which the primary site of differentiation is associated with the miRNA expression profile. We studied 50 cases of de novo diffuse large B-cell lymphoma for the expression of 15 miRNAs (miR-15a, miR-15b, miR-16, miR-17-3p, miR-17-5p, miR-18a, miR-19a, miR-19b, miR-20a, miR-21, miR-92, miR-127, miR-155, miR-181a and miR-221). Apart from 19 nodal cases without extranodal dissemination (stages I and II), we selected two groups with unambiguous stages I and II extranodal presentation; 9 cases of primary central nervous system, 11 cases of primary testicular and 11 cases of other primary extranodal diffuse large B-cell lymphomas. All cases were analyzed with qRT-PCR. In situ hybridization for the most differentially expressed miRNAs was performed to show miRNA expression in tumor cells, but not in background cells. MiR-21 and miR-19b showed the highest expression levels. No significant differences were seen between germinal center and non-germinal center diffuse large B-cell lymphomas in either the total or the nodal group for any of the 15 miRNAs. Two miRNAs showed significant differences in expression levels for diffuse large B-cell lymphoma subgroups according to the site of presentation. MiR-17-5p showed a significant higher expression level in the central nervous system compared with testicular and nodal diffuse large B-cell lymphomas (P<0.05). MiR-127 levels were significantly higher in testicular than in central nervous system and in nodal diffuse large B-cell lymphomas (P<0.05). We conclude that the location of diffuse large B-cell lymphoma is an important factor in determining the differential expression of miRNAs.

Primary Follicular Lymphoma of the Testis and Epididymis in Adults

Primary testicular lymphomas typically occur in patients over 60 years of age. Most are diffuse large B-cell lymphomas with frequent dissemination and a poor prognosis. Primary follicular lymphoma of the adult testis has not been well characterized. However, a small number of primary testicular follicular lymphomas have recently been described in children. These showed stage 1E disease, a lack of BCL2 gene rearrangement and Bcl-2 protein expression, and a good clinical outcome. Here, we describe 5 cases of primary follicular lymphoma of the testis and epididymis in adults. These presented as unilateral testicular masses 12 to 40 mm in diameter and were characterized histologically by small neoplastic follicles in a sclerotic background. The neoplastic cells expressed CD10 and Bcl-6, but not Bcl-2 and lacked t(14;18)(q32;q21)/IGH-BCL2 and BCL6 gene rearrangements. Four of the five patients were 35 years old or younger, and 4 presented with stage 1EA disease. Although follow-up is 12 months or less in 2 of the 5 patients, to date each has followed an indolent clinical course. These features are different from those of most adult nodal follicular lymphomas but are very similar to those of the pediatric primary testicular follicular lymphomas. Together, the pediatric and adult cases represent a discrete clinicopathologic entity of t(14;18)(q32;q21)/IGH-BCL2-negative primary follicular lymphoma of the testis and epididymis, which typically present as clinically indolent localized disease in young males and should be distinguished from the diffuse large B-cell lymphoma more frequently seen in the testes of older adults.