Frequency and diagnostic patterns of lymphomas in liver biopsies with respect to the WHO classification

The recent World Health Organization (WHO) classification of hematopoietic and lymphoid tissue tumors represents the first worldwide consensus classification of these malignancies. However, the applicability of this classification to a representative number of hepatic lymphomas in liver biopsy specimens has not yet been investigated. The frequency and infiltration pattern of a series of 205 liver biopsies with lymphoma manifestations was analyzed with the aid of immunohistochemical and molecular pathological analyses. Diffuse large B-cell lymphoma (DLBCL) was by far the most frequent entity, comprising 45% of the cases analyzed. Using a previously published immunohistochemical algorithm, 35% of 80 DLBCL were assigned to a germinal center B-cell-like (GCB) and 65% to a non-GCB group. Most B-cell lymphoma entities involving the liver revealed a characteristic infiltration pattern. Diagnostically challenging entities were T-cell-rich B-cell lymphomas, anaplastic large cell lymphomas and peripheral T-cell lymphomas, which frequently required additional molecular clonality assessment. Overall, the percentage of T-cell lymphomas in the liver (12%) was higher as compared to other extranodal sites except for the skin and the small intestine. This study provides relevant data on the distribution of hepatic lymphomas and demonstrates the applicability of the WHO classification proposing a diagnostic algorithm for liver biopsies.     

Histologic patterns of lung infiltration of B-cell, T-cell, and Hodgkin lymphomas

Secondary lung infiltration by lymphomas occurs frequently. To our knowledge, however, no recent studies have attempted to discriminate histologic patterns of lung infiltration in the lymphoma subtypes. We retrospectively evaluated the frequency of lung infiltration and the respective infiltration patterns by lymphomas at autopsy, during an 11-year period. Lymphomas were classified according to the 2001 World Health Organization Classification of hematologic malignancies in B-cell, T-cell, and Hodgkin lymphomas (HLs). In 21,157 autopsies, 414 reports with lymphoma diagnosis were reviewed histologically, and 85 showed lung infiltration (20.5%). We studied 14 HLs, 43 B-cell lymphomas, and 20 T-cell lymphomas. Five infiltration patterns were identified: peribronchial-perivascular, nodular alveolar, interstitial, and pleural. Approximately half of the lymphomas had more than 1 infiltration pattern (mean, 1.7); peribronchial-perivascular and pleural were the most frequent. The frequency of nodular infiltration was larger in HL than in B-cell lymphomas. T-cell lymphomas had a larger frequency of the interstitial infiltration pattern compared with B-cell lymphomas. Recognizing the frequency and patterns of lung infiltration in the light of a more recent classification is certainly useful for physicians dealing with lymphoma diagnostic procedures, such as radiologists and pathologists.     

Expression of transmembrane adaptor protein PAG/Cbp in diffuse large B-cell lymphoma: immunohistochemical study of 73 cases

PAG/Cbp is a transmembrane adaptor protein involved in proximal immune signaling. It is expressed in reactive germinal centers (GC) of secondary lymphatic follicles and related malignant lymphomas. We studied PAG/Cbp expression in GC-like and non-GC-like diffuse large B-cell lymphoma (DLBCL) subtypes. Seventy-three cases of DLBCL identified among 155 malignant lymphomas were classified as GC-like DLBCL (CD10+ or CD10-, bcl-6+, and MUM1-) and non-GC-like DLBCL (CD10-, MUM1+ or CD10-, bcl-6+, MUM1+). PAG/Cbp was detected by monoclonal antibody MEM-255 following routine immunohistochemical procedures. Thirty-five of 40 GC-like DLBCLs (88%) and 20 of 33 non-GC-like DLBCL cases (61%) expressed PAG/Cbp. Four of 12 bcl-6-negative non-GC-like DLBCL cases (33%) were PAG/Cbp positive, and only 4 of 20 bcl-6-positive non-GC-like DLBCL cases (25%) were PAG/CBP negative. All 37 FL and all 5 Burkitt's lymphomas (BL) expressed PAG/Cbp, whereas all 6 mantle cell lymphomas (MCL) and 4 of 5 chronic lymphocytic leukemias (CLL/SLL) were PAG/Cbp negative. PAG/Cbp is a reliable GC marker. Its expression correlates with GC-like DLBC phenotype in a significant majority of cases. It is typically absent in MCL and SLL/CLL.     

Aggressive B-cell lymphomas: frequency,immunophenotype, and genetics in a reference laboratory population

Diffuse large B-cell lymphoma (DLBCL) is the most common type of lymphoma worldwide. The current World Health Organization classification includes several subtypes based on a combination of clinical, immunohistochemical, and genetic differences. Other aggressive variants of B-cell lymphomas, including Burkitt lymphoma and double-hit lymphomas are part of the differential diagnosis and often have overlapping features with DLBCL. In this study, we evaluated 760 of cases of DLBCL and other aggressive B-cell lymphomas using a relatively uniform immunohistochemical panel and genetic methods. We assessed the frequency of different subtypes and locations and documented distinctive immunophenotypic and genetic findings of these cases. Most cases in the study group were DLBCL (89%), including 38 CD5+ DLBCL, 28 T-cell/histiocyte-rich large B-cell lymphomas, and 33 Epstein-Barr virus–positive DLBCL (including 6 cases in elderly patients). The study also included 39 Burkitt lymphoma and 39 cases of double-hit lymphoma. In general, our results support the World Health Organization classification approach as well as other studies of DLBCL. In this study, we focus on specific issues of interest including cell-of-origin classification testing, comparing the Hans classifier with the tally classifier, correlation of MYC immunohistochemistry with MYC fluorescence in situ hybridization, and Epstein-Barr virus positivity in aggressive B-cell lymphomas.     

A reassessment of primary thyroid lymphoma: high-grade MALT-type lymphoma as a distinct subtype of diffuse large B-cell lymphoma

AIMS: Primary lymphoma of the thyroid gland (PTL) is a relatively rare disease. During an 18-year period, 53 cases of primary non-Hodgkin's lymphoma involving this extranodal site were seen at our institutions. The aims of this study were to evaluate the spectrum of PTLs using current lymphoma classification concepts and immunocytochemical markers, determine whether features of MALT-type lymphoma were evident in PTL, and if there was any clinical significance of such a finding. METHODS AND RESULTS: The cases were retrospectively studied clinically, histologically and immunohistochemically. The tumours were classified according to the Revised European-American Lymphoma Classification of lymphoid malignancies (REAL classification). Thirty-eight patients were females, 15 were males and mean age at diagnosis was 66.3 years (range 38-90). Three cases were low-grade marginal zone lymphomas (low-grade MALT-type lymphomas). There were 45 diffuse large B-cell lymphomas (DLBCL) of which there were 27 DLBCL-NOS and 18 high-grade MALT-type lymphomas. Within the diffuse large B-cell lymphoma (DLBCL) category, cases were subdivided into those without (DLBCL-NOS) and those with features of 'high-grade' MALT-type lymphoma based on presence of a low-grade component or large cell lymphoepithelial lesions (HG MALT-type lymphoma). In addition there were three follicle centre lymphomas, one anaplastic large cell lymphoma and one peripheral T-cell lymphoma. Twenty cases were stage IE, 18 stage IIE, and four stage IV. All patients with low-grade MALT-type lymphoma are alive without disease. The 5-year survivals for DLBCL-NOS and HG MALT-type lymphoma were 75% and 25%, respectively. Univariate analysis (log rank) among the DLBCLs showed stage (P < 0.001) and subtype (P = 0.005) were associated with survival. Stage was associated with type of DLBCL, 65% of DLBCL-NOS being stage IE compared to 20% of HG MALT-type lymphomas. CONCLUSIONS: We conclude that primary thyroid lymphomas occur most commonly in elderly women and are frequently present in clinical stage IE and IIE. Low-grade MALT-type lymphomas are relatively uncommon but appear to have a favourable prognosis. DLBCL is the most common lymphoma and features of MALT can be seen in over one-third of cases. As a group, HG MALT-type lymphomas had a worse outcome than DLBCL-NOS, primarily due to higher clinical stage at diagnosis. These two subtypes of DLBCL appear to be distinct clinical and histological entities.     

The relationship between primary gastric B-cell lymphoma and immunoglobulin heavy chain (IgH) gene rearrangement--a histopathological study of primary gastric lymphomas

The aim of this study was to review our primary gastric lymphoma cases according to the new WHO classifications and to investigate the histopathological features of B-cell lymphomas. In addition, B-cell monoclonality was analyzed for immunoglobulin heavy chain (IgH) gene rearrangement using the polymerase chain reaction at the site of the lymphoma lesion, transitional lesion, and the non-lymphoma lesion. Specimens resected from 31 primary gastric lymphomas were examined. There were 28 cases (90.3%) of B-cell lymphoma and three cases (9.7%) of T-cell lymphoma. The B-cell lymphomas were classified as low-grade mucosa-associated lymphoid tissue (MALT) lymphoma (LGML) (9%), high-grade MALT lymphoma (HGML) (42%), and diffuse large B-cell lymphoma (DLBCL) (29%). Histopathologically, lymphoepithelial lesions (LEL) were higher in LGML (100%) than in DLBCL (22%), with statistical significance (p < 0.05). A monoclonal pattern of IgH rearrangement was detected in LGML (50.0%), HGML (60.0%), and DLBCL (80.6%), with a statistically significant difference between LGML and DLBCL (p < 0.01). The IgH monoclonal pattern may reflect the gross appearance of lymphoma or the lymphoma infiltration depth. Superficial spreading and shallow growth in LGML may correspond to an oligoclonal pattern, and mass-forming and deep invasive growth in DLBCL may correspond to a more monoclonal pattern.     

Lymphomas involving the spleen

Splenectomy is undertaken for diagnosis, and in later stages of management, of patients with a diverse range of lymphomas. High quality histological sections, requiring careful attention to tissue fixation, are needed to assess these lesions adequately. Increasing use of fine-needle aspiration, needle core biopsy and laparoscopic surgery add further diagnostic challenges. In addition to involvement by dissemination of lymphomas based primarily in lymph nodes, bone marrow or other tissues, spleen is the predominant site of disease in several distinctive types of lymphoma. In particular, splenic marginal zone B-cell lymphoma, hairy cell leukaemia and T-cell and macrophage-rich large B-cell lymphoma are recognized as clinicopathologically distinct entities. Research into the cellular and molecular origins of these lymphomas is ongoing; variants and new entities are becoming evident. Histological and immunohistochemical features of the spleen following treatment for lymphoma are complex and may cause diagnostic confusion. Inflammatory and reactive processes in the spleen can also provide clinical, radiological or pathological mimicry of lymphomatous involvement.     

Lymphomas involving the spleen

Splenectomy is undertaken for diagnosis, and in later stages of management, of patients with a diverse range of lymphomas. High quality histological sections, requiring careful attention to tissue fixation, are needed to assess these lesions adequately. Increasing use of fine-needle aspiration, needle core biopsy and laparoscopic surgery add further diagnostic challenges. In addition to involvement by dissemination of lymphomas based primarily in lymph nodes, bone marrow or other tissues, spleen is the predominant site of disease in several distinctive types of lymphoma. In particular, splenic marginal zone B-cell lymphoma, hairy cell leukaemia and T-cell and macrophage-rich large B-cell lymphoma are recognized as clinicopathologically distinct entities. Research into the cellular and molecular origins of these lymphomas is ongoing; variants and new entities are becoming evident. Histological and immunohistochemical features of the spleen following treatment for lymphoma are complex and may cause diagnostic confusion. Inflammatory and reactive processes in the spleen can also provide clinical, radiological or pathological mimicry of lymphomatous involvement.     

Aggressive B-cell lymphomas with a primary bone marrow presentation

Aggressive B-cell lymphomas present as a heterogeneous spectrum of disease. A primary diagnosis in the bone marrow (BM) may be challenging in terms of diagnostic classification and clinical handling, owing to limited architectural information. Aggressive B-cell lymphomas can be subdivided into entities that typically present primarily in the BM, and cases with BM involvement in which the bulk of disease is present in other organs. One main topic at the 2018 BM workshop of the European Association of Haematopathology/Society of Hematopathology was therefore aggressive B-cell lymphomas with a primary BM presentation. The spectrum of cases submitted to this topic gave a good overview of commonly encountered problems, as well as unusual manifestations, and highlighted areas of imprecise disease definitions and diagnostic grey zones. The categories submitted to the workshop included cases of Burkitt lymphoma (BL) with unusual features, high-grade B-cell lymphomas (HG-BCLs) with and without so-called double/triple-hit, and diffuse large B-cell lymphomas (DLBCLs) with a primary BM presentation. Areas of difficulties included the morphological boundaries of HG-BCL not otherwise specified, cases with MYC and bcl-2 or bcl-6 translocations and terminal deoxynucleotidyl transferase (TdT) expression, which were categorised as B-cell lymphoblastic leukaemia/lymphoma if most cells showed TdT positivity, and the clinicopathological overlap between intravascular large B-cell lymphoma, CD5-positive DLBCL, and DLBCL with primary presentations in the BM, spleen, and liver. This review summarises our understanding of the main aggressive B-cell lymphoma categories with a common primary BM presentation and potential problem areas, and makes suggestions for the immunophenotypic and genetic work-up, illustrated by the interesting and challenging cases submitted to the workshop.     

Nodal T/NK-cell lymphoma of nasal type: a clinicopathological study of six cases

Aims:  To investigate the clinicopathological features of six unusual cases of nodal CD56+ and Epstein–Barr virus (EBV)+ T/natural killer (NK)-cell lymphoma, a putative nodal counterpart of nasal NK/T-cell lymphoma (nodal T/NK-cell lymphoma of nasal type) in comparison with nasal NK/T-cell lymphoma with secondary lymph node involvement ( n  = 24) and peripheral T-cell lymphoma (PTCL) of cytotoxic molecule (CTM)+ and EBV+ type ( n  = 21).
Methods and results:  All cases of nodal T/NK-cell lymphoma of nasal type exhibited diffuse infiltration of pleomorphic medium-sized to large tumour cells, reminiscent of those in CTM+ EBV+ PTCL. The tumour cells had a typical phenotype of nasal NK/T-cell lymphoma: CD2+, CD3ε+, CD4−, CD5−, CD56+, T-cell intracellular antigen-1+, granzyme B+, perforin+ and EBV+. However, four of six cases demonstrated clonal T-cell receptor γ-gene rearrangement on polymerase chain reaction analysis, unlike nasal NK/T-cell lymphoma. Comparison of clinical parameters and overall survival among the three groups demonstrated only minor differences.
Conclusions:  Nodal T/NK-cell lymphoma may occupy the grey zone between extranodal nasal-type NK/T-cell lymphoma and nodal CTM+ PTCL in a spectrum of NK to T-cell lymphomas that are EBV+. The close relationship between NK/T-cell lymphomas and cytotoxic T-cell lymphomas was also substantiated.     

Immunohistochemistry and gene rearrangement studies in the diagnosis of malignant lymphomas: a comparison of 152 cases.

One hundred fifty-two cases (155 specimens) of lymphoproliferative disorders were studied by immunohistochemistry and gene rearrangement analysis. Ninety-five of 96 B-cell lymphomas (99%) showed genotypic B-cell monoclonality. Of these, five cases had rearranged T-cell receptor (TCR) beta chain gene in addition to immunoglobulin heavy chain (IgH) and kappa light chain (Ig-K), one case had rearranged IgH and TCR-gamma chain but not Ig-K or TCR-beta, and two cases had only Ig-K rearrangement. One exceptional case in the B-cell lymphoma group had unrearranged, germline genotypes. In contrast, only 10 of 19 (53%) phenotypic T-cell lymphomas had rearranged TCR-beta, eight with concurrent TCR-gamma rearrangement. Of the remaining nine cases, six had germline configuration, two had rearranged Ig-K only, and one had both IgH and Ig-K rearrangement. This last case was reclassified as T-cell predominant, B-cell lymphoma. Thirteen of 16 cases of Hodgkin's disease had germline configuration; three cases had rearranged IgH and Ig-K, of which two were lymphocyte predominant with light chain monoclonality and one was a recurrence. Among 21 reactive lesions, 17 had germline configuration and four had rearranged IgH and Ig-K genes. Of these four cases, two were orbital lesions, one was a partially involved lymph node, and one developed a nodular lymphoma 9 months later. Our results indicate that almost all B-cell lymphomas have IgH and/or Ig-K rearrangement. In contrast, peripheral T-cell lymphomas have greater genotypic heterogeneity, and germline patterns for TCR genes are not uncommon. Reactive lesions and Hodgkin's disease tend to retain germline configuration, and any exception is often associated with an unusual clinical setting and/or histology. Genotypic analysis is thus most indicated in B-cell lymphomas with equivocal immunohistochemistry findings, T-cell lymphomas, and atypical cases of Hodgkin's disease and reactive lesions.     

Diffuse large B-cell lymphoma showing an interfollicular pattern of proliferation: a study of the Osaka Lymphoma Study Group

Aims:  Diffuse large B-cell lymphoma (DLBCL) usually proliferates effacing lymph follicles. In occasional cases, tumour cells show an interfollicular pattern of proliferation preserving lymph follicles. The aim was to analyse clinicopathological findings in DLBCL showing an interfollicular pattern of proliferation to determine whether this type of lymphoma is a distinct entity of DLBCL.
Methods and results:  Clinicopathological findings in 12 cases of DLBCL showing an interfollicular pattern of proliferation [interfollicular group (IF)] were examined and compared with those in 30 cases of DLBCL with ordinary morphology [control group (CG)]. IF showed a significantly lower lactate dehydrogenase level and International Prognostic Index scores than CG ( P  = 0.023 and P  < 0.01, respectively). The frequency of localized disease, clinical stage 1 and 2, in IF was higher than that in CG ( P  = 0.016). A morphologically polymorphous pattern of proliferation was found in seven of 12 cases (58.3%) in IF, which was higher than that in CG, five (16.7%) of 30 cases ( P  < 0.01). Clonality analysis with the polymerase chain reaction method revealed that all 11 IF cases examined showed a monoclonal pattern. Immunohistochemically, the majority (11 of 12) of IF cases showed a non-germinal centre B-cell phenotype and the frequency was higher than that in CG ( P  = 0.021).
Conclusion:  Diffuse large B-cell lymphoma with an interfollicular pattern of proliferation shows distinct clinical and pathological findings from ordinary DLBCL.     

Composite diffuse large B-cell lymphoma and CD20-positive peripheral T-cell lymphoma

Composite lymphoma is defined as two or more distinct types of lymphoma in a single anatomical site. Among various combinations, composite B-cell and T-cell non-Hodgkin's lymphomas (CBTL) are very infrequent. Herein we describe a 66-year-old female with CBTL presenting with lymphadenopathy, multiple bone lesions and an epidural tumor. Light microscopic examination of a biopsied cervical node revealed a dual population of lymphoid cells: sheets of large cells admixed with medium-sized cells. The large cells expressed B-cell markers and showed immunoglobulin light chain restriction, consistent with diffuse large B-cell lymphoma (DLBCL). The medium-sized cells were positive for CD20 as well as T-cell markers. Because polymerase chain reaction amplification showed monoclonal rearrangement of the T-cell receptor β chain gene, this population was compatible with peripheral T-cell lymphoma not otherwise specified (PTCL-NOS). We therefore made a diagnosis of composite DLBCL and CD20-positive PTCL-NOS. Complete remission was achieved after six cycles of R-CHOP regimen (rituximab, doxorubicin, vincristine, cyclophosphamide and prednisolone). This is the first report of CD20-positive PTCL-NOS associated with composite lymphoma. Moreover, a literature review of composite DLBCL and PTCL-NOS indicates that this rare clinical entity may be featured by efficacy of systemic chemotherapy in spite of prevalent extranodal lesions.     

Clinicopathological features of aggressive B-cell lymphomas including B-cell lymphoma,unclassifiable, with features intermediate between diffuse large B-cell and Burkitt lymphomas: a study of 44 patients from Argentina

Aggressive B-cell lymphomas incorporate a wide spectrum of lymphomas that pose challenges in diagnosis as well as treatment. We evaluated the clinicopathological features of 44 patients with aggressive B-cell lymphomas which were classified into 3 groups based on the World Health Organization 2008 classification as follows: including 30 cases of diffuse large B-cell lymphoma (DLBCL), 8 cases of Burkitt lymphoma (BL) and 6 cases of B-cell lymphoma, unclassifiable, with features intermediate between Burkitt lymphoma and diffuse large B-cell lymphoma (BCLU). Male predominance was observed in BL and BCLU groups and the mean age varied from 29 years in BL, 61 years in DLBCL and 70 years in BCLU. Patients with BCLU presented at more advanced stages and had a higher international prognostic index. By immunohistochemistry, they shared characteristics of both BL (including more frequent expression of SOX11) and DLBCL. FISH analyses showed three cases with more than one rearrangement: one MYC/BCL2 and two BCL2/BCL6, in addition to which one case with BCL2/IGH translocation and another with MYC rearrangement were also detected. The mean follow-up survival time of BCLU was 6.6 months, which was significantly shorter in comparison to DLBCL (31 months) and BL (30 months), respectively. The importance of recognizing this BCLU group relies on its different clinical course, poor prognosis and shorter survival than DLBCL and BL. An accurate diagnosis is critical for risk stratification and to improve therapeutic approaches and outcomes.     

The world health organization classification of malignant lymphomas in japan: incidence of recently recognized entities. Lymphoma Study Group of Japanese Pathologists

New insights into the immunology and genetics of malignant lymphomas have allowed the recognition of new entities and the refinement of previously recognized disease categories. The relative incidence of these subtypes of malignant lymphoma is also known to differ according to geographic location. In order to clarify the current status of malignant lymphomas in Japan and the relative incidences of their subtypes, 3194 patients were classified according to the new World Health Organization (WHO) classification. Among these were 3025 cases (94.71%) of non-Hodgkin's lymphoma (2189 cases (68.53%) of B-cell lymphoma, 796 cases (24.92%) of T-cell lymphoma) and 141 cases (4.41%) of Hodgkin's lymphoma. The incidences of the major subtypes of non-Hodgkin's lymphoma were 33.34% for diffuse large B-cell lymphoma, 8.45% for marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue (MALT) type, 8.05% for plasma cell myeloma, 7.45% for adult T-cell leukemia/lymphoma (ATLL), 6.7% for follicular lymphoma, 6.67% for peripheral T-cell lymphoma of unspecified type, 2.79% for mantle cell lymphoma, 2.6% for nasal and nasal-type T/NK cell lymphoma, 2.35% for angioimmunoblastic T-cell lymphoma, and 2.35% for precursor B-cell lymphoblastic leukemia/lymphoma, in decreasing order. The other subtypes comprised less than 2%, mainly precursor T-cell lymphoblastic lymphoma/leukemia (1.72%), anaplastic large-cell lymphoma of T- and null-cell types (1.53%), and B-cell chronic lymphocytic leukemia/small lymphocytic lymphoma (1.31%). The incidence of ATLL was influenced by its high percentage (19.20%) in the south-western Japanese island, Kyushu, an endemic area of human T-cell leukemia virus type 1 (HTLV-1), but which appeared to be lower than that in a previous study. The nodular sclerosis and mixed cellularity types of Hodgkin's disease occupied 1.78% and 1.63%, respectively. These data are distinct from those in Western countries and similar in several ways to those in the East, although the relatively high rate of ATLL was attributed to the geographical difference in the etiologic factor, HTLV-1.     

Histone deacetylase 1, 2, 6 and acetylated histone H4 in B- and T-cell lymphomas

Aims:  Histone deacetylase (HDAC) inhibitors are novel therapeutics in the treatment of peripheral T-cell lymphoma, unspecified (PTCL) and diffuse large B-cell lymphoma (DLBCL), where, for unknown reasons, T-cell malignancies appear to be more sensitive than B-cell malignancies. The aim was to determine HDAC expression in DLBCL and PTCL which has not previously been investigated.
Methods and results:  The expression of HDAC1, HDAC2, HDAC6 and acetylated histone H4 was examined immunohistochemically in 31 DLBCL and 45 PTCL. All four markers showed high expression in both DLBCL and PTCL compared with normal lymphoid tissue. HDAC1 was more abundantly expressed in PTCL than in DLBCL ( P  = 0.0046), whereas acetylated H4 was more frequent in DLBCL ( P  < 0.0001), the latter suggesting a mechanism for T-cell lymphoma sensitivity to HDAC inhibitors. Moderate to strong HDAC6 expression was significantly correlated with favourable outcome ( P  = 0.016) in DLBCL patients, whereas the opposite effect was observed in PTCL patients ( P  < 0.0001). The other markers did not correlate with survival ( P  > 0.05).
Conclusions:  HDAC1, HDAC2, HDAC6 and acetylated H4 are overexpressed in DLBCL and PTCL relative to normal lymphoid tissue. Furthermore, HDAC6 may be an important prognostic marker associated with favourable outcome in DLBCL and a more aggressive course in PTCL.     

Indications for peripheral light-chain revision and somatic hypermutation without a functional B-cell receptor in precursors of a composite diffuse large B-cell and Hodgkin's lymphoma

Composite lymphomas are rare combinations of Hodgkin's lymphoma (HL) and non-Hodgkin's lymphoma in the same patient, where clonal relatedness has been observed in most of the few cases analyzed. Here, we report a composite classical HL and diffuse large B-cell lymphoma (DLBCL) with interesting molecular features. Micromanipulation of single cells and analysis of V gene rearrangements revealed clonal relatedness with shared and distinct mutations, indicative of derivation from a common germinal center (GC) B-cell precursor and also of further development of both lymphomas in a GC. In the DLBCL, a very high mutation load, including inactivating mutations, and two copies of the same clonal rearrangement with different mutations in single cells were observed. Intriguingly, in the DLBCL precursor somatic hypermutation activity continued after acquisition of destructive V gene mutations, a feature previously found only in Epstein-Barr virus (EBV) infected B-cell expansions. Furthermore, we found evidence of light-chain receptor revision in the lymphoma precursor during a GC reaction. Re-expression of the V(D)J recombination machinery may enhance genomic instability in GC B cells and contribute to lymphomagenesis.     

Das Lymphom im Magen

Differentiation of chronic gastritis from marginal zone B-cell lymphoma (MZoL) of MALT type is often difficult for the pathologist. Diagnostic tools include CD20 stain to highlight lymphoepithelial lesions, Wotherspoon grading of the infiltrate, and clonality analysis of the B-cells. MZoL may partially transform into a diffuse, large B-cell lymphoma, which the authors have named blastic MZoL. Blastic MZoL may be present with or without small cell MZoL. Without this component, blastic MzoL, while being CD10-negative, is presently difficult to positively diagnose since specific immune markers are still lacking. Blastic MZoL has a very favourable outcome compared to conventional diffuse large B-cell lymphomas (DLBCL). Moreover, there are conventional DLBCL in the stomach, mostly in a setting of a secondary organ involvement. The biology of these gastric DLBCL is identical to their extragastric counterparts. This is also true for primary gastric Burkitt lymphoma and mucosal involvement in B-CLL or mantle cell lymphoma. Unfavourable outcomes are always observed for EBV-triggered lymphoproliferations in immunodeficiency and peripheral T-cell lymphomas which might also arise or be initially diagnosed in the stomach.     

Gastrointestinal lymphomas: entities and mimics

The gastrointestinal tract is the most common extranodal site of lymphoma involvement. Although B-cell lymphomas are by far the most frequent type found in this location, gastrointestinal lymphomas are a diverse group of neoplasms, many of which are characterized by distinctive clinicopathologic settings. Diffuse large B-cell lymphoma and marginal-zone lymphoma of mucosa-associated lymphoid tissue are commonly encountered, but other less-common entities can pose diagnostic challenges, mimicking both benign, reactive conditions and each other. We describe several different lymphoma subtypes, with a focus on frequently encountered challenges in differential diagnosis.