CD56+ putative natural killer cell lymphomas: production of cytolytic effectors and related proteins mediating tumor cell apoptosis?

Summary and comparison of the perforin in teleosts and mammals: A review

Perforin, a pore-forming glycoprotein, has been demonstrated to play key roles in clearing virus-infected cells and tumour cells due to its ability of forming 'pores' on the cell membranes. Additionally, perforin is also found to be associated with human diseases such as tumours, virus infections, immune rejection and some autoimmune diseases. Until now, plenty of perforin genes have been identified in vertebrates, especially the mammals and teleost fish. Conversely, vertebrate homologue of perforin gene was not identified in the invertebrates. Although recently there have been several reviews focusing on perforin and granzymes in mammals, no one highlighted the current advances of perforin in the other vertebrates. Here, in addition to mammalian perforin, the structure, evolution, tissue distribution and function of perforin in bony fish are summarized, respectively, which will allow us to gain more insights into the perforin in lower animals and the evolution of this important pore-forming protein across vertebrates.

Identification of T-cell receptor expression in EBV-positive neoplastic cells in extranodal NK/T-cell lymphoma, nasal-type, and comparison with T-cell receptor gene rearrangement by BIOMED-2 assay

The cellular lineage of extranodal NK/T-cell lymphoma, nasal-type (ENKTL), is determined by expression of T-cell receptor (TR) or TR gene rearrangement. In ENKTL, from TR immunohistochemistry, it may often be difficult to decide whether TR-positive cells are tumor cells or not, especially when TR is expressed in a subset of tumor cells. To analyze TR expression pattern and TR rearrangement in T-lineage ENKTL, we performed double immunofluorescence staining for Epstein-Barr virus-encoded small RNAs (EBER)/T-cell receptor (TCR) βF1 and CD56/TCR βF1 in 12 cases of ENKTL that showed TCR βF1 expression in immunohistochemistry. TR gene rearrangement was analyzed using a commercial BIOMED-2 multiplex polymerase chain reaction system. Immunohistochemistry showed that all 12 cases expressed TCR βF1 in a wide range of infiltrating cells from 100% to <1%. Two of them expressed both TCR βF1 and TCR cγM1. EBER/TCR-βF1-positivity was confirmed in 10 cases by double staining. One case failed to show EBER/TCR-βF1-positive cells but showed a CD56/TCR βF1-positive result. Among 12 cases, 5 had poor-quality DNA, 3 of them showed no polymerase chain reaction product, and 2 cases showed nonspecific peak of low height. Five of 7 cases with good DNA quality demonstrated monoclonal TR gene rearrangement. Based on TR expression and TR gene rearrangement, 10 of 12 cases of ENKTL were decided as a T-lineage tumor. In conclusion, because of common TR silence and poor DNA quality, consideration of both immunohistochemistry and TR gene rearrangement is necessary to determine the lineage of ENKTL.

Flow cytometric detection and quantification of CD56 (neural cell adhesion molecule, NCAM) expression in diffuse large B cell lymphomas and review of the literature

AIM

To report unusual CD56 (neural cell adhesion molecule, NCAM) expression on diffuse large B cell lymphoma (DLBCL).

METHODS AND RESULTS

CD56 expression was first detected and quantified on tissues obtained from five cases of DLBCL by flow cytometry (FC), then confirmed by immunohistochemistry. The CD56 expression pattern was heterogeneous among the cases [the molecular equivalent of soluble fluorochrome (MESF) level ranged from 2214 to 133 466]. All were CD10 and Bcl-6 positive, suggesting their germinal centre origin; one was also CD5 positive. An extranodal presentation occurred in three of five cases.

CONCLUSIONS

CD56 expression in B cell lymphoma is a rare occurrence. FC is able to identify aberrant immunophenotypes that can be useful in the identification and monitoring of B cell lymphoma subtypes. The presence of CD56 reported by the literature on certain DLBCL with extranodal presentation might be related to mechanisms involved in growth and expansion.

Pathobiology of Epstein-Barr virus-driven peripheral T-cell lymphomas

In the present review, the authors described the pathobiological features of Epstein-Barr virus (EBV)-driven T/natural killer cell-derived malignancies. These rare tumors appear to be quite heterogeneous with regard to both clinical and pathologic features. Nonetheless, some elements, especially regarding the possible role of EBV (ie, genomic predisposition, pathogenesis, pattern of latency), are similar, enforcing the concept of a causative role for the virus. In clinical practice, although definitely rare in Western countries, the tumors are not exceptional; thus, they should be taken into account in the differential diagnosis of T-lymphoproliferative disorders, also considering the need for extremely prompt intervention. The prognosis of such tumors is generally poor using current approaches. A better understanding of their molecular pathogenesis may lead to significant therapeutic improvements. For example, the nuclear factor-KB pathway and platelet-derived growth factor receptor inhibition may represent 2 options to be tested in clinical trials.

Aberrant antigenic expression in extranodal NK/T-cell lymphoma: a multi-parameter study from Thailand

Background

Extranodal NK/T-cell lymphoma, nasal type (ENKTL) is not common worldwide, but it is the most common T- and NK-cell lymphomas in many Asian countries. Immunophenotypic profiles were studied based on limited series. The authors, therefore, studied on ENKTL according to characterize immunophenotypic profiles as well as the distribution of EBV subtype and LMP-1 gene deletion.

Methods

By using tissue microarray (TMA), immunohistochemical study and EBV encoded RNA (EBER) in situ hybridization were performed. T-cell receptor (TCR) gene rearrangement, EBV subtyping, and LMP-1 gene deletion were studied on the available cases.

Results

There were 22 cases eligible for TMA. ENKTL were positive for CD3 (91%), CD5 (9%), CD7 (32%), CD4 (14%), CD56 (82%), TIA-1 (100%), granzyme B (95%), perforin (86%), CD45 (83%), CD30 (75%), Oct2 (25%), and IRF4/MUM1 (33%). None of them was positive for βF1, CD8, or CD57. TCR gene rearrangement was negative in all 18 tested cases. EBV was subtype A in all 15 tested cases, with 87% deleted LMP-1 gene. Cases lacking perforin expression demonstrated a significantly poorer survival outcome (p = 0.008).

Conclusions

The present study demonstrated TIA-1 and EBER as the two most sensitive markers. There were a few CD3 and/or CD56 negative cases noted. Interestingly, losses of CD45 and/or CD7 were not uncommon while Oct2 and IRF4/MUM1 could be positive in a subset of cases. Based on the present study in conjunction with the literature review, determination of PCR-based TCR gene rearrangement analysis might not be a useful technique for making diagnosis of ENKTL.

Extranodal NK/T-cell lymphoma, nasal type (angiocentric T-cell lymphoma): A review about the terminology

Extranodal NK/T-cell lymphoma, nasal type (ENKL) is a rare lymphoid neoplasm, which in the past has been grouped with a variety of granulomatous diseases. It is an aggressive non-Hodgkin’s type characterized clinically by aggressive, nonrelenting destruction of the midline structures of the palate and nasal fossa. Despite the malignant clinical course, histological diagnosis can be difficult because of extensive tissue necrosis and multiple biopsies that are often required and has an ominous prognosis, as the average survival rate is between 6 and 25 months as reported with a large number of Asian studies. Several American and European studies have shown similar results. This is the case report of a 60-year-old male patient who presented with nasal obstruction and foul smelling, ulcerative lesion over the palate of 6 months duration, which had been treated with antibiotics and anti-inflammatories without success. After performing a number of diagnostic tests, it was found histologically and confirmed by immunohistochemical analysis that the patient had an ENKL, nasal type (also known as angiocentric T-cell lymphoma).

Extranodal NK/T-cell lymphoma: toward the identification of clinical molecular targets

Extranodal natural killer (NK)/T-cell lymphoma of nasal type (NKTCL) is a malignant disorder of cytotoxic lymphocytes of NK or more rarely T cells associated with clonal Epstein-Barr virus infection. Extranodal NKTCL is rare in Western countries, but in Asia and Central and South America it can account for up to 10% of non-Hodgkin's lymphomas. It is an aggressive neoplasm with very poor prognosis. Although the pathogenesis of extranodal NKTCL remains poorly understood, some insights have been gained in the recent years, especially from genome-wide studies. Based on our own experience and knowledge of the literature, we here review some of the genomic and functional pathway alterations observed in NKTCL that could provide a rationale for the development of innovative therapeutic strategies.

Perforin: more than just a pore-forming protein

Cellular apoptosis induced by T cells is mainly mediated by two pathways. One, granule exocytosis utilizes perforin/granzymes. The other involves signaling through death receptors of the TNF-alpha R super-family, especially FasL. Perforin plays a central role in apoptosis induced by granzymes. However, the mechanisms of perforin-mediated cytotoxicity are still not elucidated completely. Perforin is not only a pore-forming protein, but also performs multiple biological functions or perforin performs one biological function (cytolysis), but has multiple biological implications in the cellular immune responses, including regulation of proliferation of CD8+ CTLs.

Expression of CD56 and WT1 in ovarian stroma and ovarian stromal tumors

The immunophenotype of ovarian stroma and spindle cell tumors derived from ovarian stroma has not been well studied. We studied the expression of CD56, WT1, estrogen receptor-beta (ER-beta), progesterone receptor (PR), smooth muscle actin, S-100, CD34, and muscle specific actin in 16 normal ovaries, 17 ovarian fibromas, 11 ovarian cellular fibromas, 10 ovarian fibrothecomas, and 11 ovarian leiomyomas. In addition, we studied CD56 and WT1 expression in 7 cases of normal endometrium, 8 uterine smooth muscle tumors, 5 endometrial stromal tumors and 64 nongynecologic (GYN) spindle cell sarcomas. All normal ovaries, ovarian fibromas, fibrothecomas, and ovarian leiomyomas were positive for CD56 and WT1. Most of the normal ovaries, ovarian fibromas, ovarian fibrothecomas, and ovarian leiomyomata also expressed ER-beta and PR. Eight of 17 ovarian fibromas, 5 of 11 ovarian cellular fibromas, and 4 of 10 ovarian fibrothecoma with focal fibroblastic differentiation were positive for smooth muscle actin. A few cases of these tumors also expressed S-100 and CD34. Only rare cases of non-GYN spindle cell sarcomas expressed WT1. Our study results show that ovarian fibromas, fibrothecomas, and leiomyomas have a similar immunophenotype (positive for CD56, WT1, ER-beta, and PR) to that of ovarian stromal cells, supporting an ovarian stromal origin for these neoplasms. However, unlike normal ovarian stromal cells, ovarian fibromas, fibrothecomas, and leiomyomas can also show fibroblastic, smooth muscle, Schwannian, and solitary fibrous tumorlike differentiation. WT1 is a fairly specific marker for spindle cell tumors of gynecologic organs, including ovarian spindle cell tumors, endometrial stromal tumors, and uterine smooth muscle tumors. Non-GYN spindle cell sarcomas rarely express WT1. CD56 is strongly expressed in ovarian stromal cells but not in endometrial stromal cells. CD56 is often expressed by a wide variety of spindle cell sarcomas, thus, it has no value in differentiating GYN from non-GYN spindle cell tumors.

Necrotizing sialometaplasia of the palate associated with angiocentric T-cell lymphoma

In this article we present 2 cases of necrotizing sialometaplasia (NS) associated with angiocentric lymphoma of the midline. Immunohistochemical analysis confirmed a T-cell origin, and in situ hybridization in one case revealed its relationship to Epstein-Barr virus. These findings suggest that vascular occlusion by the neoplastic cells produces ischemia, which leads to local infarction contributing to the salivary gland lesion. To our knowledge, the association between angiocentric lymphoma and NS has been previously reported in only one instance, and we suggest that this particular type of lymphoma should be added to the list of related conditions for NS.

Extranodal NK/T-cell lymphoma, nasal type: study of clinicopathologic and prognosis factors in a series of 78 cases from Peru

It is well known that extranodal NK/T-cell lymphoma (NK/TCL) nasal type clusters in Asian countries. A large series of 78 cases of nasal NK/TCL from Peru is analyzed in the present study. Two histologic groups 1 (monomorphic) and 2 (polymorphic), were segregated according to the proportion of large cells (above and below 30%, respectively). Catalyzed signal amplification technique was performed for enhancement of immunohistochemistry reactivities. Epstein-Barr virus (EBV) sequences and types were investigated using polymerase chain reaction. Clinical characteristics, stage, outcome, and response to treatment were evaluated in both groups. Fourteen cases (18%) and 64 cases (82%) corresponded to groups 1 and 2, respectively. Except for nasal obstruction, more common in group 2, all other symptoms were similar in both groups. Local extension and staging were also comparable. Both groups showed CD3c+ CD2+ CD56+ CD3s- CD20- immunophenotype. All cases were positive for EBV. In this series type-2 EBV was found more frequent than type-1 EBV, contrarily to that observed in Asian series. However, about one-third of cases simultaneously harbored both viral types. Both groups received an average of 50-Gy dose of radiation therapy (RT), with or without chemotherapy. Complete therapeutic response was achieved in 89% of group 1 and in 74% of group 2, but this difference was not statistically significant. There were no significant differences between the groups regarding disease-free survival, failure-free survival, relapse, and overall survival. The overall survival, in both groups, was longer for patients treated with RT alone compared with those treated with combined RT therapy and chemotherapy. The present study has shown that dividing nasal NK/TCL in monomorphic and polymorphic variants, according to frequency of large cells, does not correlate with clinical and prognostic factors.

The pathology of NK-cell lymphomas and leukemias

Natural killer (NK) cell lymphomas and leukemias are a rare but clinically important group of neoplasms. Most of these tumors are aggressive, with a high rate of mortality. They include extranodal NK/T-cell lymphomas of nasal type and aggressive NK-cell leukemias. Both are Epstein-Barr virus (EBV) associated and show similar epidemiologic features. A closely related entity seen mainly in children is hydroa vacciniforme-like lymphoma, which also is EBV positive. EBV influences the pathophysiology of these tumors, through the induction of cytokines and chemokines. The differential diagnosis of NK-cell malignancies includes fulminant EBV-associated T-cell lymphoproliferative disorder, a condition referred to in the past as fatal infectious mononucleosis. Benign proliferations of NK cells can be seen in association with viral infection. The disease formerly referred to as blastic NK-cell lymphoma is now considered to be a malignancy derived from a dendritic cell precursor.

Natural killer cell neoplasms: a distinctive group of highly aggressive lymphomas/leukemias

Natural killer (NK) cell neoplasms, which include extranodal NK/T-cell lymphoma (nasal and extranasal) and aggressive NK cell leukemia, are generally rare, but they are more common in people of Oriental, Mexican and South American descent. These neoplasms are highly aggressive, and show a strong association with Epstein-Barr virus. Extranodal NK/T-cell lymphoma most commonly affects the nasal cavity and other mucosal sites of the upper aerodigestive tract. Patients present with nasal obstruction or midfacial destruction. Despite the early stage of disease at presentation, overall survival is poor. Patients with the extranasal form of the lymphoma often present with high-stage disease, commonly involving the skin, gastrointestinal tract, testis, and soft tissue, and the prognosis is even worse. Histologically, the lymphoma can show a broad cytologic spectrum, but apoptosis, necrosis, and angioinvasion are common. The most common immunophenotype is CD2(+), surface CD3(-), cytoplasmic CD3(+), CD56(+). Based on currently available data, treatment of nasal NK/T-cell lymphoma should consist of radiotherapy, with or without multiagent chemotherapy. More research is required to ascertain the role of high-dose chemotherapy with stem cell rescue and that of non-multidrug resistance-related chemotherapeutic agents. Aggressive NK cell leukemia affects younger patients, who present with poor general condition, fever, and disseminated disease; they often die within a short time from systemic disease or complications such as multi-organ failure. The peripheral blood and bone marrow show atypical large granular lymphocytes, which exhibit an immunophenotype similar to that of extranodal NK/T-cell lymphoma. Aggressive NK cell leukemia must be distinguished from T-cell large granular lymphocyte leukemia and indolent NK cell lymphoproliferative disorder, both of which are indolent.

Sinonasal NK/T-cell lymphomas in the United States

Sinonasal natural killer (NK)/T-cell lymphomas are common in Asia and areas of South and Central America but are rarely seen in the United States, where they have not been as well characterized. Fifteen cases diagnosed in Southern California were studied with respect to histologic features, immunophenotype, Epstein-Barr virus EBER in-situ hybridization (EBV EBER-ISH), and T-cell receptor gamma chain (TCR-gamma) gene rearrangement. Although ethnic background was available for only seven patients, six were of Asian or Hispanic descent with only one non-Hispanic white known. Twelve presented as sinonasal lesions, but three were limited to the oropharynx. Most cases (11 of 15) demonstrated both necrosis and an angiodestructive pattern. All cases demonstrated cytoplasmic CD3 positivity (15 of 15), and were positive for both TIA-1 and granzyme B (14 of 14). Perforin was positive in 5 of 14. CD56 was expressed in 10 of 15 and CD8 in 3 of 15. EBV EBER-ISH was positive in 14 of 14 and TCR-gamma gene rearrangement was detected in 1 of 14 cases. None (0 of 14) were positive for CD16 or CD57. Although CD16-positive histiocytes were abundant, double-label EBER-ISH/IHC failed to identify CD16 expression on EBV-positive tumor cells. Three cases with pleomorphic large cell morphology showed focal CD30 positivity, raising the differential diagnosis of anaplastic large cell lymphoma, but all were ALK-1-negative and otherwise similar to the other cases of NK/T-cell lymphoma. Sinonasal NK/T-cell lymphomas in the United States most often occur in ethnic groups from areas of reported high frequency (Asia, Central and South America), although less commonly than in endemic populations, and are otherwise similar phenotypically. A combined approach, including immunohistochemistry, EBV EBER-ISH, and TCR gene rearrangement studies, is most helpful to arrive at the correct diagnosis.

Lymphomatous features of aggressive NK cell leukaemia/lymphoma with massive necrosis, haemophagocytosis and EB virus infection

AIMS

Aggressive natural killer (NK) cell leukaemia will be categorized as a distinct entity in the new WHO classification of malignant lymphomas. However, its non-leukaemic features remain unclear. We therefore investigated the morphological and immunophenotypic features of this lymphoma.

METHODS AND RESULTS

Four cases with aggressive NK cell lymphoma were morphologically and immunohistochemically studied. All cases followed an aggressive course with death occurring within about 3 months of initial presentation. In these cases, the neoplastic cells disseminated throughout systemic lymph nodes and invaded various tissues and organs. The lymphoma cells were large cells showing nuclear irregularity and a pattern of sinusoidal invasion in lymph nodes. Apoptosis and coagulation necrosis were both frequently observed. Haemophagocytosis was observed in all cases. Neoplastic cells in paraffin-embedded tissue specimens from these patients had CD3(CD3epsilon)+ CD56(123C3)+ granzyme+ TIA-1+ EBERT+ CD43(MT1)- CD45RO(UCHL-1)- CD57(Leu7)- CD20(L26)- phenotypes. In the two cases where tissue was available for immunohistochemical study in frozen sections, neoplastic cells showed CD56(Leu19)+ perforin+ Fas ligand(FasL)+ CD2(Leu5b)- CD3(Leu4)- CD4(Leu3)- CD5(Leu1)- CD7(Leu9)- CD8(Leu2)- betaF1- TCRdelta1- phenotypes. CD16(Leu11b) was positive in one case.

CONCLUSIONS

: Natural killer cell lymphomas appear to represent a non-leukaemic counterpart of aggressive natural killer cell leukaemia, a relationship similar to that in adult T-cell leukaemia/lymphoma. Awareness and diagnosis of this aggressive lymphoma is important because of its fulminant course.

Expression of cytotoxic proteins in peripheral T-cell and natural killer-cell (NK) lymphomas: association with extranodal site, NK or Tgammadelta phenotype, anaplastic morphology and CD30 expression

Most peripheral T-cell lymphomas (PTCL) express the alphabeta T-cell receptor (TCR) whereas rare PTCL express the gammadelta TCR. Most if not all gammadelta PTCL are extranodal lymphomas and among them, hepatosplenic gammadelta PTCL constitute a distinct clinicopathological entity. Besides alphabeta and gammadelta PTCL, there is a recently recognized group of extranodal, mainly nasal tumours, which display, in most instances, phenotypic and genotypic features of Natural-Killer cell non-Hodgkin's lymphomas (NK-NHL). Cytotoxic cells, including NK cells and cytotoxic alphabeta and gammadelta T lymphocytes may induce lysis of the target by using granule-associated cytotoxic proteins such as the T-cell intracellular antigen-1 (TIA-1), perforin and granzyme B. Expression of TIA-1 can be detected in all cytotoxic cells whereas granzyme B and perforin expression can be detected in high levels only in activated cytotoxic cells. Recently, several studies showed that the expression of these cytotoxic proteins in tumour cells of PTCL and NK-NHL is associated with a) extranodal site of clinicopathological presentation b) NK or Tgammadelta-cell phenotype c) CD30 expression in cutaneous T-cell lymphoproliferations and d) anaplastic morphology in nodal PTCL. This latter finding contrasts with the data that only rare Hodgkin lymphomas (HL) express cytotoxic proteins in Hodgkin and Reed-Sternberg cells. Altogether the data of the literature indicate that most extranodal T and NK-NHL are activated cytotoxic lymphomas with the notable exception of hepatosplenic gammadelta PTCL which represent tumours of non-activated cytotoxic cells. On this basis, it is suggested that the expression of cytotoxic proteins may be useful for the identification and classification of extranodal T and NK-cell lymphomas and, to some extent, for the differential diagnosis between HL and CD30+ anaplastic large cell lymphomas. Cytotoxic lymphomas are preferentially localized in extranodal sites such as skin, lung, upper respiratory and gastrointestinal tracts, which are continuously exposed to various antigens. Since cytotoxic T and NK cells are regarded as first line of defense in these sites, and some cytotoxic tumours such as nasal lymphomas and enteropathy-type intestinal lymphomas are associated with EBV and gliadin, respectively, it is likely that chronic antigen exposure may play a role in the pathogenesis of cytotoxic lymphomas occurring in mucosa and/or skin. Besides chronic antigenic stimulation, chronic immunosuppression may also have pathogenetic significance in cytotoxic lymphomas in view of their increased incidence in immunocompromised patients.

Expression of cyclin-dependent kinase 6 (cdk6) and frequent loss of CD44 in nasal-nasopharyngeal NK/T-cell lymphomas: comparison with CD56-negative peripheral T-cell lymphomas

Lymphomas involving the nasal and nasopharyngeal region mainly include CD56-positive natural killer (NK)/T-cell lymphomas, CD56-negative peripheral T-cell lymphomas (PTL), and B-cell lymphomas. Among these, the CD56-positive lymphoma, presumably of an NK/T-cell nature, is frequently seen in Asian, Mexican, and South American patients. NK cells are proposed to be closer developmentally to T cells than to other lymphoid cells, because bipotential common progenitor cells of NK/T-cell lineage have been isolated. In this study, we collected 47 cases of nasal lymphoma and investigated the phenotypic difference between NK/T-cell lymphoma and PTL by examining the pattern of the developmentally differentially expressed molecules cdk6 (cyclin-dependent kinase 6), CD44, CD117, and by examining the rearrangement of the T-cell receptor gene (TcR-GR). cdk6, an essential regulator of the cell cycle in G1 progression, was over-expressed in a subset of cortical thymocytes, but absent in mature thymocytes. In contrast, CD44, a glycosylated adhesion molecule, was absent in cortical thymocytes, but present in mature thymocytes and peripheral activated T cells. We found both over-expression of nuclear cdk6 (n-cdk6) and frequent absence of CD44 in nasal CD56-positive NK/T-cell lymphomas, in contrast to most nasal CD56-negative PTL, which were CD44-immunoreactive with weak or no expression of n-cdk6. Almost all tested cases of NK/T-cell lymphoma displayed a germ-line configuration of TcR, without evidence of gene rearrangement. Thus, there seems to be a useful distinction between the classical NK/T type of nasal lymphoma (CD56+/n-cdk6+/CD44-/TcR-GR-) and PTL (CD56-/n-cdk6-/CD44+/TcR-GR+) involving the nasal region. The presence of Epstein-Barr virus does not seem to be a good marker for distinguishing between NK/T lymphoma and PTL involving the nasal region.

Angiodestruction and tissue necrosis of skin-involving CD56+ NK/T-cell lymphoma are influenced by expression of cell adhesion molecules and cytotoxic granule and apoptosis-related proteins

We compared the expression of cell adhesion molecules (CAMs), cytotoxic granule proteins, and apoptosis-related proteins by immunohistology and in situ terminal deoxynucleotidyl transferase-mediated digoxigenin-dUTP nick end labeling (TUNEL) of 10 cases of cutaneous CD56+ NK/T cell lymphoma with and 6 cases without angiodestruction. Lymphoma cells in cases with angiodestruction frequently expressed CAMs CD2, CD11a, and CD49d and their ligands CD58, CD54, and CD106 and were positive for CD122 and cytotoxic granule proteins TIA1, perforin, and granzyme B. Lymphoma cells in cases without angiodestruction mostly were negative for CD2, CD58, CD54, CD106, and TIA1 and weakly positive for perforin and granzyme B. In the TUNEL method, mean apoptotic indices (AI) for cases with angiodestruction showed a higher percentage than those without angiodestruction. CD95L, CD95, apoptosis-induced cysteine protease CPP32, apoptosis-promoting protein Bax, and proliferating marker (MIB1) frequently were positive in the lymphoma cells of cases with angiodestruction, but there was no expression of apoptosis-inhibitor protein Bcl2. In most cases without angiodestruction, lymphoma cells were positive for CD95L and Bax and negative for CD95, CPP32, and MIB1. CAMs and the 3 cytotoxic granule proteins and an apoptosis pathway might be important factors in the paracrine and autocrine mechanisms of tissue necrosis in cutaneous CD56+ NK/T cell lymphoma.

Diffuse large B cell lymphoma expressing the natural killer cell marker CD56

The expression of the natural killer (NK) cell antigen, CD56, in hematological malignancies is rare. However, there are several reports that some hematological malignancies, such as T/NK cell lymphoma, multiple myeloma (MM) and acute myeloid leukemia (AML), express this molecule. In B cell non-Hodgkin's lymphomas (NHL), however, very limited number of cases have been reported to express CD56 molecule. Although one study has recently described that half of microvillous B cell lymphoma (MVL), an uncommon subset of large cell lymphoma, expressed CD56, there have been no reports about most common type of B-NHL, diffuse large B cell lymphoma (DLBL) other than a mention of weak CD56 expression in one of 83 DLBL. We herein presented the first case of diffuse large B cell lymphoma expressing CD56 clearly. The immunophenotype determined by immunostaining and flow cytometric analysis was CD10+, CD19+, CD20+, CD45RO-, CD3- and CD56+. On immunohistochemical study, neither bcl-2 nor TIA-1 was positive for tumor cell. Monoclonal immunoglobulin heavy chain (IgH) gene rearrangement was detected, and the sequence analysis of the variable region of IgH (VH) suggested that this tumor was derived from antigen selected post germinal center B cell. Conventional combination chemotherapy (CHOP) was administered, and the patient has still been in complete remission for 10 months.

Histological and immunophenotypic profile of nasal NK/T cell lymphomas from Peru: high prevalence of p53 overexpression

Nasal NK/T-cell lymphoma is a unique form of lymphoma highly associated with Epstein-Barr virus (EBV). These lymphomas are rare in Western populations and much more prevalent in some Asian and Latin American countries. Although there are several sizable studies from Asian countries, the same is not true from South America. The aim of this study was to analyze a series of 32 cases of nasal T-cell lymphoma from Peru and to further extend the characterization of this disease. Immunohistochemistry was performed on paraffin sections using the following antibodies: CD20 (L26), CD45RO, CD3, Ki67, CD57, CD56, TIA-1, bcl-2, and p53. The presence of EBV was investigated with immunohistochemical analysis for latent membrane protein (LMP)-1 and in situ hybridization using an antisense riboprobe to EBER 1. The 32 patients included 18 men and 14 women (M:F ratio, 1.2:1), with a median age of 43 years (11 to 72). Three categories were identified: (1) Nasal NK/T cell lymphomas (28 cases): The morphology ranged from small or medium-sized cells to large transformed cells. Necrosis was present in 86% of the cases, and angioinvasion was seen in 36% of the cases. All cases were positive for CD45RO, CD3, and for TIA-1. CD56 was positive in 21 of 27 cases (78%), and CD57 was negative in all cases. EBER 1 positivity was identified in most of the tumor cells in 27 of 28 cases (96%), including the six cases in which CD56 was negative. Overexpression of p53 was detected in 24 cases (86%). (2) Blastic NK cell lymphoma (1 case): The neoplastic cells resembled those of lymphoblastic lymphoma. CD56 and CD45RO were positive; TIA-1, TdT, and EBER-1 were negative. (3) Peripheral T-cell lymphoma (PTCL) unspecified (3 cases): CD56, TIA-1, and EBER-1 were negative. Nasal lymphomas from Peru with a T cell phenotype are predominantly EBV-associated NK/T cell lymphomas, similar to those described in Asian countries. The expression of CD56, TIA-1, and EBER-1, in combination, are very useful markers for the diagnosis of nasal NK/T cell lymphoma in paraffin-embedded tissue. The differential diagnosis of T-cell lymphomas in the nasal region should include rare cases of PTCL unspecified and the blastic variant of NK cell lymphoma. P53 is overexpressed in 86% of the cases. The significance of this finding with regard to clinical behavior and prognosis remains to be determined.

Phenotypic and cytotoxic characteristics of peripheral T-cell and NK-cell lymphomas in relation to Epstein-Barr virus association

AIMS

We investigated the phenotypic and cytotoxic characteristics of different types of peripheral T-cell and NK-cell lymphomas and correlated the findings of cytotoxic phenotype with Epstein-Barr virus (EBV) association.

METHODS AND RESULTS

Eighty cases of peripheral T-cell and NK-cell lymphomas, classified according to the REAL classification, were investigated for cytotoxic phenotype (by studying T-cell intracellular antigen-1 (TIA-1) expression immunohistochemically) and EBV association (by in situ hybridization for EBV-encoded small non-polyadenylated RNAs), and the results were correlated with the specific clinicopathological types and the immunophenotype with special emphasis on CD56 expression and CD4/CD8 status. Overall, 39/80 cases (49%) expressed TIA-1. Angiocentric lymphoma (23/24 cases; 96%), aggressive NK-cell leukaemia ('large granular lymphocyte (LGL) leukaemia') (3/3 cases; 100%), intestinal T-cell lymphoma (5/6 cases; 83%) and anaplastic large cell lymphoma (4/6 cases; 67%) were the major subtypes showing a cytotoxic phenotype. Only four of the 27 cases (15%) of peripheral T-cell lymphoma, unspecified, were TIA-1+, while all the seven cases of angioimmunoblastic T-cell lymphoma, six cases of mycosis fungoides and one case of adult T-cell lymphoma/leukaemia were TIA-1-.

CONCLUSIONS

Within the group of peripheral T-cell and NK-cell lymphomas, angiocentric lymphoma, aggressive NK-cell leukaemia ('LGL leukaemia'), intestinal T-cell lymphoma and anaplastic large cell lymphoma are the major subtypes displaying a cytotoxic phenotype. The relationships between the cytotoxic phenotype and EBV association, CD56 expression or CD4/CD8 status are secondary to the relationship between cytotoxic phenotype and specific lymphoma subtype.

Peripheral T and putative natural killer cell lymphomas commonly coexpress CD95 and CD95 ligand

The CD95 (Fas)/CD95 ligand (CD95L) system is an important mechanism triggering apoptosis, and CD95L expression has recently been implicated for immune evasion and aggressive behavior in malignancies. This study aimed to investigate CD95 and CD95L expression in lymphomas and the possible relationship with tumor cell apoptosis, with emphasis on the natural killer (NK) cell lymphomas, which are highly aggressive neoplasms and frequently exhibit tumor cell apoptosis/necrosis. Frozen sections of 82 cases of lymphomas obtained from Queen Elizabeth Hospital and Caritas Medical Center, Hong Kong, were immunostained with polyclonal anti-CD95 and anti-CD95L antibodies. The NK-cell lymphomas were also studied for apoptosis by in situ end labeling (ISEL) method, and zonal tumor cell death was evaluated semiquantitatively. The cases studied included 27 NK-, 22 T-, and 33 B-cell lymphomas. CD95 was expressed in 25 (93%) NK-, 11 (50%) T-, and 14 (42%) B-cell lymphomas. CD95L was expressed in 19 (70%) NK-, 15 (68%) T-, and 3 (9%) B-cell lymphomas. There was significant difference in the frequency of CD95 expression between B- and NK- (P < .001), and between T- and NK-cell lymphomas (P < .05), and in CD95L expression between B- and T- (P < .01) or NK-cell (P < .01) lymphomas. Zonal tumor cell death was present in 21 (78%) NK-cell lymphomas and 1 (4.5%) T-cell lymphoma and showed no correlation with CD95 or CD95L expression. ISEL analysis showed apoptosis predominantly in the viable areas in only 5 (24%) NK-cell lymphomas. In conclusion, CD95L is frequently expressed in NK- and T-cell lymphomas, but rarely in B-cell lymphomas. Zonal tumor cell death is not correlated with CD95 or CD95L expression and thus the CD95/CD95L system probably does not contribute significantly to this phenomenon. We postulate that the frequent expression of CD95L by NK- and T-cell lymphomas may mediate local or systemic tissue damage and immune evasion, and may contribute to the clinical aggressiveness of these tumors.