Usefulness of follicular dendritic cell pattern in classification of peripheral T-cell lymphomas

A personalized approach to lymphoproliferations in patients with inborn errors of immunity

Biopsies from patients with inborn error of immunity (IEI) may pose a diagnostic challenge due to the abnormal anatomy of their lymphoid organs and the tendency for the development of lymphoproliferations in various organs, some of which may lead to the wrong impression of malignant lymphoma which may prompt aggressive unnecessary treatment. In this article we will review typical histologic findings in various IEI's described in the literature and discuss the appropriate approach to the diagnosis of lymphoproliferations in these patients by presenting illustrative cases.

Recent Advances in Diagnosis and Therapy of Angioimmunoblastic T Cell Lymphoma

Angioimmunoblastic T cell lymphoma (AITL) is a common subtype of mature peripheral T cell lymphoma (PTCL). As per the 2016 World Health Organization classification, AITL is now considered as a subtype of nodal T cell lymphoma with follicular helper T cells. The diagnosis is challenging and requires a constellation of clinical, laboratory and histopathological findings. Significant progress in the molecular pathophysiology of AITL has been achieved in the past two decades. Characteristic genomic features have been recognized that could provide a potential platform for better diagnosis and future prognostic models. Frontline therapy for AITL was mainly depending on chemotherapy and the management of relapsed or refractory AITL is still unsatisfactory with a very poor prognosis. Upfront transplantation offers better survival. Novel agents have been introduced recently with promising outcomes. Several clinical trials of combinations using novel agents are underway. Herein, we briefly review recent advances in AITL diagnosis and the evolving treatment landscape.

Use of Smooth Muscle Myosin Heavy Chain as an Effective Marker of Follicular Dendritic Cells

Smooth muscle myosin heavy chain (SMMHC) is a major structural component of the contractile apparatus in smooth muscle cells. Even though it is considered a relatively specific marker for terminal smooth muscle cell differentiation, expression in other cell types such as follicular dendritic cells (FDCs) has rarely been reported. To determine whether SMMHC represents an effective FDC marker in lymphoid tissues, we compared the immunohistochemical results for SMMHC with those of the traditional FDC markers podoplanin (D2-40) and CD21. Paraffin sections of 44 lymphoid tissues were analyzed, including 31 cases of follicular hyperplasia, 6 cases of follicular lymphoma, 2 cases of peripheral T-cell lymphoma, 3 cases of diffuse large B-cell lymphoma arising in follicular lymphoma, 1 case of nodular sclerosis classical Hodgkin lymphoma, and 1 case of small lymphocytic lymphoma. There was no statistically significant difference between the number of SMMHC-positive and D2-40-positive or CD21 lymph nodes (P>0.05). The extent and intensity of SMMHC-positive FDCs were similar to those of D2-40-positive FDCs (P=0.127 and 0.733, respectively), but significantly lower compared with those of CD21 cells (P=0.009 and 0.00002, respectively). However, in contrast to CD21 which was also positive in some germinal center B cells, SMMHC expression was restricted to FDCs. Our results indicate that SMMHC is an excellent marker for FDCs and can be particularly helpful in demonstrating the underlying architecture in lymphoid processes.

Clinicopathologic characteristics of angioimmunoblastic T-cell lymphoma: analysis of the international peripheral T-cell lymphoma project

PURPOSE

The International Peripheral T-Cell Lymphoma Project was undertaken to better understand the subtypes of T-cell and natural killer (NK) -cell lymphomas.

PATIENTS AND METHODS

Angioimmunoblastic T-cell lymphoma (AITL) was diagnosed according to the 2001 WHO criteria by a central review process consisting of panels of expert hematopathologists. Clinical, pathologic, immunophenotyping, treatment, and survival data were correlated.

RESULTS

Of 1,314 patients, 243 (18.5%) were diagnosed with AITL. At presentation, generalized lymphadenopathy was noted in 76% of patients, and 89% had stages III to IV disease. Skin rash was observed in 21% of patients. Hemolytic anemia and hypergammoglobulinemia occurred in 13% and 30% of patients, respectively. Five-year overall and failure-free survivals were 33% and 18%, respectively. At presentation, prognostic models were evaluated, including the standard International Prognostic Index, which comprised the following factors: age ≥ 60 years, stages III to IV disease, lactic dehydrogenase (LDH) > normal, extranodal sites (ENSs) > one, and performance status (PS) ≥ 2; the Prognostic Index for Peripheral T-Cell Lymphoma, comprising: age ≥ 60 years, PS ≥ 2, LDH > normal, and bone marrow involvement; and the alternative Prognostic Index for AITL (PIAI), comprising: age > 60 years, PS ≥ 2, ENSs > one, B symptoms, and platelet count < 150 × 10(9)/L. The simplified PIAI had a low-risk group (zero to one factors), with 5-year survival of 44%, and a high-risk group (two to five factors), with 5-year survival of 24% (P = .0065).

CONCLUSION

AITL is a rare clinicopathologic entity characterized by an aggressive course and dismal outcome with current therapies.

Ratio of M2 macrophage expression is closely associated with poor prognosis for Angioimmunoblastic T-cell lymphoma (AITL)

Angioimmunoblastic T-cell lymphoma (AITL) is a peripheral T-cell lymphoma characterized by systemic disease with polymorphous infiltrate including macrophages. Although many studies of tumor-associated macrophage (TAM) populations in various malignant tumors have been published, only a few have dealt with activation of macrophage phenotypes such as M1 and M2 in tumor tissue. Because M2 macrophages highly express CD163, we suspected that CD163 may be a useful marker for identification of activation of macrophage phenotypes in AITL. We performed a retrospective study of immunohistochemical expression using two markers for macrophages [CD68 (PG-M1), CD163] and of the correlation of these expressions with overall survival of 42 AITL patients. The number of CD68-positive cells in AITL tissues did not correlate with overall survival (P= 0.59), whereas the number of CD163-positive cells and overall survival correlated to some extent (P= 0.08). Meanwhile, a higher ratio of CD163-positive to CD68-positive cells in AITL significantly correlated with worse overall survival (P= 0.036). Considering that this ratio reflects the proportion of macrophages polarized to the M2 phenotype, our findings indicate that activation of macrophages towards the M2 phenotype correlates with worse prognosis. Our findings indicate that the ratio of M2 macrophages expressed may be a useful marker for prognosis of AITL.

Immunohistochemical analysis for CD21, CD35, Caldesmon and S100 protein on dendritic cells types in oral lymphomas

Objective:

Follicular dendritic cells (FDCs) and interdigitating dendritic cells (IDCs) are dendritic cells found in lymphoid follicles, reactive follicles and in lymphomas. The goal of this study was to evaluate the presence and distribution of FDCs and IDCs in oral lymphomas.

Material and Methods:

Immunohistochemistry reactions were applied to 50 oral lymphomas using the antibodies anti-CD21, anti-CD35 and anti-caldesmon to FDCs, and anti-S100 protein to IDCs. Caldesmon+/FDCs and S100+/IDCs were quantified in Imagelab® software.

Results:

FDCs revealed by CD21 and CD35 were positively stained in two cases of diffuse large B-cell lymphoma, one MALT lymphoma, and in one case of mantle cell lymphoma. FDCs were immunopositive to caldesmon in all cases, as well as IDCs to S100 protein. Burkitt lymphoma presented a lower amount of caldesmon+/FDCs and S100+/IDCs than diffuse large B-cell lymphoma and plasmablastic lymphoma of the oral mucosa type.

Conclusions:

The microenvironment determined by neoplastic lymphoid cells in oral lymphomas is responsible by the development and expression of dendritic cells types.

Angioimmunoblastic T-cell lymphoma: clinical and laboratory features at diagnosis in 77 patients

We retrospectively analyzed 77 patients with pathologically diagnosed angioimmunoblastic T-cell lymphoma from a single city. There were 43 men and 34 women; the median age was 64.5 years (range, 30-91 yr). Average time between first symptoms of the disease and diagnosis was 3.6 months. At diagnosis, peripheral nodes were present in all but 1 patient, and were generalized in 90% of cases. Constitutional symptoms were reported in 77% of cases and spleen enlargement in 51%. A cutaneous eruption--morbilliform, urticarial, or more polymorphic--was present in 45% of patients; in one-third of them, the eruption occurred after drug administration. Other clinical manifestations included pleuritis (22%); arthralgia or arthritis (17%); ear, nose, and throat involvement (14%); central or peripheral neurologic manifestations (10%); and ascites (5%). Most patients presented with advanced disease at diagnosis (bone marrow involvement in 60% of cases). The main laboratory abnormalities were elevated lactate dehydrogenase levels (71%), inflammatory syndrome (67%), hypergammaglobulinemia (50%), anemia (51%), and lymphopenia (52%). Auto- or disimmune manifestations were reported in one-third of patients: autoimmune hemolytic anemia was present at diagnosis in 19% of patients and thrombocytopenic purpura in 7%. Documented vasculitis was described in 12% of cases. Clonality was analyzed in lymph nodes in 47 patients: T-cell and B-cell clones were found in 45 (96%) and 20 (45%) patients, respectively. Chromosomal abnormalities were identified in 62% of cases: trisomies 3, 5, 18, 19, additional X chromosome, and deletion of chromosome 7 were the most common abnormalities. The current study underlines the diversity of presenting manifestations of angioimmunoblastic T-cell lymphoma.

Adult T-cell Lymphoma/Leukemia With Angioimmunoblastic T-cell Lymphomalike Features: Report of 11 Cases

In adult T-cell lymphoma/leukemia (ATLL), the neoplastic lymphoid cells are usually medium-sized to large, often with pronounced nuclear pleomorphism compatible with the diagnosis of diffuse pleomorphic peripheral T-cell lymphoma. We describe here 11 patients with the rare morphologic variant of ATLL, angioimmunoblastic T-cell lymphoma (AILT)-like type. The examined lymph nodes showed proliferation of high endothelial venules and presence of various infiltrating inflammatory cells including plasma cells and eosinophils. The lymphoma cells were medium-to-large size with clear cytoplasm. These findings were suggestive of AILT. However, immunohistochemical features of AILT, namely, CD10 and CXCL13 expression in lymphoma cells and proliferation of CD21-positive follicular dendritic cells, were not detected. Two cases were CXCR3-positive, whereas 9 expressed CCR4, which are usually positive in ATLL. All patients were positive for antiadult T-cell leukemia/lymphoma-associated antigen, which is a specific antibody for human T-cell lymphotropic virus type-I. Southern blot analysis revealed proviral DNA integration in lymphoma cells in 9 patients. The latter was not evident in the first biopsy of 2 patients but in the second biopsy obtained within several months after the first biopsy revealed definite proviral integration. Almost all patients showed aggressive clinical course and poor survival (median survival: 5 mo). This is the first report of ATLL with AILT-like morphologic features.

Follicular Dendritic Cell Immunohistochemical Markers in Angioimmunoblastic T-Cell Lymphoma

Angioimmunoblastic T-cell lymphoma is characterized by a paracortical proliferation of medium to large neoplastic T cells, often with clear cytoplasm, in a background of arborizing high endothelial venules, many surrounded by follicular dendritic cells (FDCs). IHC staining may be applied to highlight these extrafollicular FDCs, traditionally using CD21, or CD23. Several alternative FDC markers have been described, including CNA.42, cystatin A/acid cysteine proteinase inhibitor (ACPI, involved in antigen presentation), and fascin (an actin binding protein). The authors stained a collection of 45 angioimmunoblastic T-cell lymphomas with CD21, CD23, CNA.42, cystatin A, and fascin for direct comparison of FDC staining characteristics in this setting. CD21 highlighted the expected dendritic network of cell processes, within residual follicles and outside of follicles, often adjacent to proliferating vessels. CD23 exhibited similar staining quality but was less sensitive than CD21. CNA.42 showed only diffuse weak labeling of FDCs. Cystatin A stained the cytoplasm of follicular dendritic cells within and outside of follicles; however, staining was often not sharply localized to dendritic cell processes, and scoring was further complicated by reactivity with other cell types in over half of the cases. Likewise, fascin stained a variety of cell types, including strong staining of interdigitating dendritic-like cells, moderate staining of endothelial cells, and only weak staining of follicular dendritic cells within and outside of follicles. Thus, CD21 remains the most reliable marker of follicular dendritic cells in angioimmunoblastic T-cell lymphoma.

Diagnostic application of Epstein-Barr virus-encoded RNA in situ hybridisation

AIMS

Epstein-Barr virus (EBV) has been implicated in the pathogenesis of nasopharyngeal carcinoma and a range of proliferative lymphoid conditions. In situ hybridisation (ISH) looking for virus-encoded RNA (EBER) transcripts is performed simply using a commercially available probe. We aimed to examine the application of this test in a routine diagnostic setting.

METHODS

In total, 26 cases in which EBV ISH was requested for diagnostic purposes were examined. We looked at the indication for testing, the result and its implication for the final diagnosis.

RESULTS

Cases were classified into three categories: possible nasopharyngeal carcinoma; possible EBV-related lymphoma; and possible immunodeficiency-associated lymphoproliferative disorder. Six of nine cases of possible nasopharyngeal carcinoma were EBV ISH positive (3/3 primary and 3/6 secondary), confirming the diagnosis. Three of 14 possible lymphoma cases were EBV ISH positive which, along with appropriate ancillary tests, assisted in making the diagnoses of Burkitt's lymphoma, lymphomatoid granulomatosis and extranodal NK/T-cell lymphoma of nasal type. All of three immunodeficiency-associated cases were EBV ISH positive. Two of these were post-transplant lymphoproliferative disorders, monomorphic type. The third case was classified as HIV-related polymorphic lymphoproliferative disorder.

CONCLUSIONS

In our experience, EBV ISH is a straightforward and rapid procedure to perform, giving unequivocal results. Used in the appropriate clinicopathological setting it can be a highly useful ancillary diagnostic aid.

The role of the perifollicular sinus in determining the complex immunoarchitecture of angioimmunoblastic T-cell lymphoma

The growth of angioimmunoblastic T-cell lymphoma (AIL) in lymph node often produces complex patterns of neoplastic T cells and nonneoplastic B cells that complicate diagnosis. To understand better how these different patterns of B-cell expansion arise, we compared the microanatomic localization of B cells and T cells within the follicular, paracortical, and sinusoidal compartments in 30 patients with AIL (including 10 with multiple sequential samples) with that seen in 33 cases of other types of T-cell lymphoma. With early or partial nodal involvement in AIL, germinal center B-cell expansions were relatively undisturbed and often associated with a variably distended D2-40+ CD31+ perifollicular sinus that surrounded most of the follicular compartment. Identifiable tumor T cells resided mostly in the paracortex. In later stages of AIL with more complete nodal effacement, bcl-6+ follicular B-cell proliferations shifted to distorted FDC networks arrayed along patent trabecular sinuses and were more intermixed with tumor T cells. In both AIL and other T-cell lymphomas, the density and locations of follicular B cells as well as bcl-6-negative monocytoid B cells were largely related to the patency of adjacent sinuses, except in Epstein-Barr virus (EBV)+ and histiocyte-rich B-cell proliferations, which arose in paracortical locations. The prominence of the perifollicular sinus in early stages of AIL resembled that seen in reactive lymphadenitis during conditions of lymphatic engorgement and implicates cytokines within lymph fluid in maintaining both the normal and altered germinal center reactions. Patterns of sinus drainage largely explain the useful changes in B-cell distribution that occur in nodal T-cell lymphomas and represent an important tool in classification and diagnosis of these tumors.

Disappearance of CD21-positive follicular dendritic cells preceding the transformation of follicular lymphoma: immunohistological study of the transformation using CD21, p53, Ki-67, and P-glycoprotein

Some follicular lymphomas histologically transform into diffuse aggressive lymphomas, the prognosis of which is poor. There are, however, no reliable histological criteria for predicting which cases will later undergo such transformation. In low-grade B-cell lymphomas, follicular dendritic cells form dense mesh-like networks that contain accumulating neoplastic B-cells. These are rare in high-grade lymphomas. We immunohistochemically analyzed CD21-positive follicular dendritic cells in 32 follicular lymphomas, including 3 transformed lymphomas, in addition to immunohistological study using P-glycoprotein, p53, and Ki-67. We found that the mesh-like networks in follicles are more clearly defined in low-grade lymphomas than in high-grade lymphomas (p = 0.015). Neoplastic follicles in 2 transformed lymphomas lost the networks of follicular dendritic cells before transformation despite the existence of morphologically clear follicles. This differed from the non-transformed cases of the same cytological grades. Prognosis was statistically better for patients with low-grade tumor than for those with high-grade tumor (p = 0.026), and there was a trend toward poorer survival among CD21-negative cases (p = 0.186). P-glycoprotein, p53, and Ki-67 expressions did not provide sufficient information to predict the transformation of follicular lymphoma. The presence of CD21-positive follicular dendritic cells in neoplastic follicles might help predict the potential of follicular lymphoma to transform to diffuse large B-cell lymphoma.

Follicular dendritic reticulum cell tumor mimicking inflammatory pseudotumor of the spleen

In the course of a routine clinical check up of the 54 year old male a splenic well circumscribed tumor like mass of 12 cm in diameter was discovered. Splenectomy with removal of splenic hilar lymph nodes and liver wedge biopsy were performed. Four years later the patient is symptom free. In the removed spleen the tumor like lesion showed a pattern consistent with the diagnosis of inflammatory pseudotumor. However, besides lymphocytes, plasma cells, macrophages, eosinophils and myofibroblasts a high number of slightly polymorphic, frequently binucleated cells positive for CD21 and CD23 were seen. These cells which were scattered or formed smaller or larger groups and fascicles were considered to represent follicular dendritic reticulum cells (FDRCs) and the lesion a FDRC tumor. Flow cytometric DNA ploidy analysis showed a hyperdiploid cell population inside the tumor like lesion. Besides FDRC tumors of high and of intermediate malignancy the present case may represent a low grade type of moderate proliferation activity. The FDRCs of the lesion and a few smaller spindle cells were EBER positive indicative of the presence of EBV. No EBER positive cells were seen in the uninvolved spleen.

CD10 Expression in Extranodal Dissemination of Angioimmunoblastic T-cell Lymphoma

Angioimmunoblastic T-cell lymphoma (AITL) is a systemic disease that often has evidence of extranodal involvement at presentation. In a recent study of lymph nodes in AITL, we showed that the neoplastic T cells in most cases can be identified by aberrant expression of CD10. The aim of this study was to investigate whether CD10 expression by the neoplastic T cells is maintained in extranodal sites. Ten cases of AITL with histologic and immunophenotypic evidence of extranodal dissemination were studied. Seven cases of peripheral T-cell lymphoma unspecified (PTLu), that included biopsies of involved extranodal sites, two cases of enteropathy type T-cell lymphoma (ETTL), and one case of extranodal NK/T lymphoma, nasal type were selected as controls. Diagnostic lymph node biopsies and biopsies of extranodal sites were reviewed. PCR for T-cell clonality and single layer immunostaining for CD3, CD20, CD10, and CD21 and double layer immunostaining for CD20/CD10 were performed. All 10 cases of AITL had characteristic histologic features and molecular evidence of the disease in lymph node biopsies. In these cases, aberrant CD10 expression was maintained in the lung, cecum, tonsil, nasopharynx, and one of six involved bone marrow trephines. In these extranodal biopsies, the distribution of CD10-positive tumor cells correlated with that of the follicular dendritic cell meshwork (FDC). The five bone marrow trephines that lacked aberrant CD10 expression were devoid of morphologic and immunohistochemical evidence of FDC. In these five cases, there was evidence of aberrant CD10 expression in other involved sites that had FDC. The neoplastic cells in PTLu, ETTL, and extranodal NK/T lymphoma, nasal type were CD10 negative. Our data show that aberrant CD10 expression is a useful phenotypic marker for diagnosis of AITL in most involved extranodal sites, except bone marrow, and suggest a possible role of FDC in the pathogenesis of AITL.

Angioimmunoblastic T cell lymphoma is derived from mature T-helper cells with varying expression and loss of detectable CD4

Angioimmunoblastic T cell lymphoma (AILT) is a rare lymphoma that is regarded as a clinicopathologic entity but shows considerable histomorphologic diversity, variable immunophenotypes and inconsistent T cell receptor (TCR) gene rearrangement. One hundred four paraffin blocks of AILT were investigated defining tumor cell lineage by triple immunostains with a confocal laser scanning microscope and correlating morphology, immunophenotype and TCRgamma gene rearrangement to clinical outcome. Ninety-nine cases were CD4(+), some of them showing a mixture of CD4(+) and CD4(-) tumor cells. The remaining 5 specimens were CD3(+)/CD4(-)/CD8(-). A considerable number of T cells of different subtypes could always be found, but even in 13 cases predominated by CD8(+) cells, proliferation could be attributed to atypical CD4(+) cells. TCRgamma gene rearrangement was monoclonal in 48 cases (69%) among 70 tested. In 29 of these semi-quantitative gene scan analysis resulted in a median proportion of monoclonal peak of 35% of PCR-products. Clinical outcome was identical grouping patients by clonality of TCRgamma, absence or presence of clear cell clusters and international prognostic index. We conclude that AILT is mainly derived from CD2(+)CD3(+)CD4(+)CD5(+)CD7(-) mature T-helper cells with varying expression and partial loss of detectable CD4. A significant number of non-neoplastic T cells (resting CD4(+) T cells and activated small or medium-sized CD8(+) lymphocytes) may coexist with a minor neoplastic T cell population. Clinicopathologic correlation suggests AILT to be a well defined homogeneous entity with poor prognosis. Currently no prognostic factors can be derived.

Peripheral T-cell lymphoma with a nodular growth pattern

Peripheral T-cell lymphomas (PTCL) with nodular growth patterns are very rare, with only 17 cases reported previously. Here, we report a case of PTCL with a nodular growth pattern. The patient was an 81-year-old Japanese woman who complained of malaise, fever and generalized lymph node swelling. Cervical lymph node biopsy was performed, and histological examination revealed proliferation of medium- to large-sized atypical lymphoid cells with indented to irregular nuclei, distinct nucleoli and clear cytoplasm. The nodular growth pattern of the lymphoma cells was obvious. On immunohistochemistry, the atypical lymphoid cells proved to be of T-helper cell origin (CD2+CD3CD4+CD5+CD7+ CD8-CD10-CD25-CD30-CD57-). Polymerase chain reaction analysis of the T-cell receptor gamma-chain revealed a monoclonal rearrangement band. This unusual growth pattern should be distinguished among PTCL, as such cases could be confused with reactive nodular hyperplasia, nodular lymphoma, mantle cell lymphoma and marginal zone lymphoma with nodular colonization.

Neoplastic T cells in angioimmunoblastic T-cell lymphoma express CD10

Angioimmunoblastic T-cell lymphoma (AITL) is a systemic disease involving lymph nodes, spleen, and bone marrow. Although the histologic features have been well described, the diagnosis is often challenging, as there are no specific phenotypic or molecular markers available. This study shows that the neoplastic cells of AITL can be identified by aberrant CD10 expression. Archival material from 30 cases of AITL, 10 cases of peripheral T-cell lymphoma unspecified (PTL), and 10 cases of reactive lymphoid hyperplasia were reviewed. Single and double immunostaining for CD3, CD4, CD8, CD20, CD21, CD10, BCL6, Ki67, and LMP-1 in situ hybridization for Epstein-Barr early region and polymerase chain reaction (PCR) for T-cell receptor gamma chain gene and immunoglobulin heavy chain gene were performed. Three overlapping histologic patterns with hyperplastic follicles, depleted follicles, or without follicles were identified in AITL. Of the 30 cases of AITL, 27 contained CD10(+) T cells. No CD10(+) T cells were present in the cases of PTL or reactive hyperplasia. PCR confirmed a monoclonal or oligoclonal T-cell population in 29 of 30 cases of AITL and a monoclonal B-cell population in 6 cases. Analysis of microdissected CD10(+) single cells showed that they belonged to the neoplastic clone. In conclusion CD10 is a phenotypic marker that specifically identifies the tumor cells in 90% of AITL, including the early cases. The presence of these cells distinguishes AITL from other PTLs. This finding provides an objective criterion for accurate and early diagnosis of AITL.

Follicular dendritic cells in reactive and neoplastic lymphoid tissues: a reevaluation of staining patterns of CD21, CD23, and CD35 antibodies in paraffin sections after wet heat-induced epitope retrieval

Structural alterations in the meshwork of follicular dendritic cells (FDCs) are frequently found in malignant lymphomas. Formaldehyde fixation and paraffin embedding, however, have long prevented consistent detection of FDCs. Wet heat-induced epitope retrieval in Dako Target Retrieval Solution (TRS) (pH 6.0) enabled the reliable detection of FDCs through CD21, CD23, and CD35 antigens in routinely processed tissues from 11 reactive and 69 neoplastic lymphoproliferations, thus allowing the distribution of the FDCs to be reevaluated. Germinal center FDCs in lymphoid hyperplasias and expanded FDC meshworks in the 8 mantle cell lymphomas, 7 low-grade MALT lymphomas, and 6 low-grade follicular lymphomas were intensely stained with all these markers. In 6 cases of B cell chronic lymphocytic leukemia, tumor cells were CD23+. In four cases of nodular lymphocyte predominance Hodgkin's disease (HD), expanded FDC meshwork's sharply delineating negative tumor cells and their rosetting T cell, were revealed mainly with the CD21 and CD35 antibodies. Follicular dendritic cells were also demonstrated in 11 cases of grade I nodular sclerosing HD, including follicular HD. Striking dendritic cell clusters were revealed with all 3 antibodies in 9 angioimmunoblastic T cell lymphomas. Sparse or no FDC meshworks were detected in the 4 cases of grade II nodular sclerosing HD, 5 follicular lymphomas with high-grade transformation, and 5 T cell-rich B cell lymphomas. CD35 immunostaining showed the most consistent labeling in the four FDC sarcomas studied in the current article. Reproducible demonstration of FDCs in routinely processed paraffin sections with CD21, CD23, and CD35 antibodies, as presented here, provides invaluable pieces of information in the diagnosis of lymphoproliferative disorders.

Peripheral T/NK-cell lymphoma: a report of the IXth Workshop of the European Association for Haematopathology

AIMS

In April 1998, The European Association for Haematopathology organized the IXth workshop on peripheral T-cell and NK-cell lymphomas and leukaemias. The workshop focused on unusual subtypes of these rare malignancies, allowing evaluation of the recently published WHO classification of neoplastic diseases of the lymphoid tissues.

METHODS AND RESULTS

One-hundred and three cases were centrally immunophenotyped and hybridized for EBER1/2 of Epstein--Barr virus. All cases were reviewed by a panel of experienced haematopathologists and classified according to the new WHO classification for lymphoid neoplasms. Three cases were considered as precursor T-cell and 95 cases as peripheral T/NK-cell lymphoma/leukaemia. Although the cases represented a selected series of unusual cases, the following conclusions could be made: (i) Most lymphomas except the hepatosplenic gamma/delta T-cell lymphomas showed a rather broad morphological spectrum, with differences both between and within individual tumours. (ii) This heterogeneity was also reflected by the immunophenotype, for instance a variable expression of CD30 was found in many enteropathy type T-cell lymphomas. (iii) Exceptions in phenotype were regularly found in almost all categories, indicating that phenotype should not be the final determining factor in classification. (iv) The great majority of T-cell lymphomas expressed the alpha/beta T-cell receptor, with the exception of all but one hepatosplenic T-cell lymphomas and a few other extranodal peripheral T cell lymphomas. (v) Malignancies of precursor cells, blastic NK-cell lymphoma/leukaemia, adult T-cell lymphoma/leukaemia and most AIL-type T-cell lymphomas did not express cytotoxic molecules such as TIA1 and granzyme-B. In contrast, all five aggressive NK/T-cell lymphomas/leukaemias, a single case of large granular lymphocyte leukaemia and 40 of 47 primary extranodal lymphoma/leukaemias expressed these molecules. In hepatosplenic gamma/delta T-cell lymphoma, five of six cases showed expression of TIA1 but not of granzyme-B. (vi) Seven tumours developed after organ-transplant, four cases being EBV-positive. No distinct phenotype could be attributed to these cases.

CONCLUSIONS

Most peripheral T/NK cell lymphomas could be categorized as distinct entities as described in the recently proposed WHO classification for lymphoid neoplasms.

Peripheral T-cell lymphoma with follicular involvement and a CD4+/bcl-6+ phenotype

A truly follicular pattern is thought to be restricted to B-cell lymphomas. We observed a prominent follicular growth pattern in three cases of nodal peripheral T-cell lymphomas, of which two were initially diagnosed as follicular lymphomas. All three patients were male, ranged in age from 50 to 70 years, and had generalized lymphadenopathy at the time of diagnosis. The follicles were sharply demarcated in two cases and large and vague in one case; in all cases, they contained abundant follicular dendritic cells. Neoplastic cells were small to medium, with irregular cleaved or round nuclei and clear cytoplasm, which was abundant in one case. Lymphoma cells in all cases were CD4+ CD8- CD57- bcl-6, with CD10 coexpression in 2 cases. Clonal rearrangement of the gamma chain of the T-cell receptor gene was demonstrated in each case. These cases expand the differential diagnosis of lymphomas with a follicular growth pattern and suggest that neoplastic T cells may have the capacity to induce or home to follicular structures.

Prognostic value of follicular dendritic cells in nodular sclerosing Hodgkin's disease

AIMS

In nodular sclerosing Hodgkin's disease (NSHD), the prognostic relevance of the histopathological grading in two subtypes NSI (low-grade) and NSII (high-grade) remains controversial. Analysis of follicular dendritic cells (FDC) may provide new prognostic parameters.

METHODS AND RESULTS

Tumours from 59 patients with NSHD were studied. Mean follow-up time was 8 years. Forty-one cases were classified as NSI and 18 as NSII. FDC were immunostained with the paraffin-resistant monoclonal antibodies CD21 and CNA.42. We distinguished three patterns in the neoplastic tissue: FDC1, the presence of well-defined follicle-like structures (n = 20); FDC2, the presence of largely destroyed FDC networks (n = 25); and FDC3, no or a few isolated FDC (n = 14). The three groups differed clearly regarding the frequency of relapse and the survival. The longest survival was seen in the FDC1 group, the shortest in the FDC3 group, the FDC2 group being intermediate (P = 0.0025). FDC status was a discriminating prognostic factor for all patients, and within various age and stage categories. Combining the FDC status and the NSI-NSII grading defined the best survival group as FDC1-NSI.

CONCLUSIONS

Assessment of FDC pattern, associated with histological subtyping, brings valuable data for predicting survival and outcome in NSHD.

Contemporary classification of histiocytic disorders. The WHO Committee On Histiocytic/Reticulum Cell Proliferations. Reclassification Working Group of the Histiocyte Society

Pathologists and pediatric hematologist/ oncologists of the World Health Organization's Committee on Histiocytic/Reticulum Cell Proliferations and the Reclassification Working Group of the Histiocyte Society present a classification of the histiocytic disorders that primarily affect children. Nosology, based on the lineage of lesional cells and biological behavior, is related to the ontogeny of histiocytes (macrophages and dendritic cells of the immune system). Dendritic cell-related disorders of varied biological behavior are dominated by Langerhans cell histiocytosis, but separate secondary proliferations of dendritic cells must be differentiated. Juvenile xanthogranuloma represents a disorder of dermal dendrocytes, another dendritic cell of skin. The hemophagocytic syndromes are the most common of the macrophage-related disorders of varied biological behavior. Guidelines for distinguishing the exceedingly rare malignant diseases of histiocytes from large cell lymphomas through the use of a battery of special studies are provided.

Peripheral T-cell lymphomas. Clinico-pathologic study of 168 cases diagnosed according to the R.E.A.L. Classification

BACKGROUND

One hundred sixty-eight peripheral T-cell lymphomas (PTCLs) were reviewed according to the Revised European-American Lymphoma (R.E.A.L.) Classification.

PATIENTS AND METHODS

The cases, originally diagnosed on the basis of the Updated Kiel Classification (UKC), were all provided with histological preparations, immunophenotype, clinical information, and follow-up data. The slides were reclassified by five observers, who integrated the R.E.A.L. criteria with cell size measurements. The prognostic value of clinical and pathologic findings was assessed by univariate and multivariate analysis.

RESULTS

The R.E.A.L. Classification was reproducibly applied by all of the observers. Clinically, anaplastic large cell lymphomas (ALCLs) differed from the remaining PTCLs by mean age (29.5 vs. 52.9 years), bulky disease (52.3% vs. 11.3%; P = 0.000), mediastinal mass (52.7% vs. 32%; P = 0.004), and disease-free survival (68.0% vs. 38.2%; P = 0.0001). Although each histological type displayed specific clinical aspects, PTCLs other than ALCL were basically characterised by a poor clinical outcome which was not influenced by the UKC malignancy grade. At multivariate analysis, the risk of a lower complete remission rate was related to bulky disease (P = 0.001), histologic group (non-ALCL) (P = 0.01), and advanced stage (III-IV) (P = 0.0002).

CONCLUSIONS

The present study supports the classification of T-cell lymphomas proposed by the R.E.A.L. scheme.