Classification Of Peripheral T-cell Lymphomas Research Articles

Aggressive T-cell lymphomas: 2024: Updates on diagnosis, risk stratification, and management.

Aggressive T-cell lymphomas continue to have a poor prognosis. There are over 30 different subtypes of peripheral T-cell lymphoma (PTCL), and we are now beginning to understand the differences between the various subtypes beyond histologic variations. Gene expression profiling and other molecular techniques have enabled deeper understanding of differences in various subtypes as reflected in the latest 5th WHO classification of PTCL. It is becoming increasingly clear that therapeutic approaches that target specific cellular pathways are needed to improve the clinical outcomes of PTCL. There are many targeted agents currently in various stages of clinical trials for PTCL that take advantage of the differential expression of specific proteins or receptors in PTCL tumors. This includes the CD30 directed antibody drug conjugate brentuximab vedotin. Other notable targets are phosphatidylinositol 3-kinase inhibitors, histone deacetylase inhibitors, CD25, and chemokine receptor 4. Anaplastic lymphoma kinase (ALK) inhibitors are promising for ALK expressing tumors. Allogeneic stem cell transplant continues to be the curative therapy for most aggressive subtypes of PTCL. The use of checkpoint inhibitors in the treatment of PTCL is still controversial, with best results seen in cases of extranodal natural killer cell/T-cell lymphoma. Bispecific antibody-based treatments and chimeric antigen receptor cell-based therapies are in clinical trials.

What is new in the classification of peripheral Tcell lymphomas?

In this review focus article, we highlight the main modifications introduced in the latest 2022 International Consensus Classification and World Health Organization classification (ICC and WHO-HAEM5) of matureT (and NK) cell neoplasms (PTCLs) and consequent implications for diagnostic practice. The changes result from recent advances in the genomic and molecular characterization of PTCLs and enhanced understanding of their pathobiology. Specifically, consideration is given to the following groups of diseases: Epstein-Barr virus (EBV)-associated neoplasms; follicular helper Tcell lymphoma; anaplastic large cell lymphomas; primary intestinalT and NK cell lymphomas and lymphoproliferative disorders; and PTCL, not otherwise specified.

Novel T Follicular Helper-like T-Cell Lymphoma Therapies: From Preclinical Evaluation to Clinical Reality.

Simple SummaryThis work reviews the multiple efforts that have been and are being invested by researchers as well as clinicians to improve the treatment of a specific T-cell lymphoma called follicular helper peripheral T-cell lymphoma. Still, though treatments for B-cell lymphomas have improved, this particular T-cell lymphoma has little to no new therapeutic options that show marked improvements in the survival of the patients compared to treatment with chemotherapy. We report here the evaluation of targeted new therapies for this T-cell lymphoma in new preclinical models for this cancer or in clinical trials with the objective to offer better (combination) treatment options.The classification of peripheral T-cell lymphomas (PTCL) is constantly changing and contains multiple subtypes. Here, we focus on Tfh-like PTCL, to which angioimmunoblastic T-cell lymphoma (AITL) belongs, according to the last WHO classification. The first-line treatment of these malignancies still relies on chemotherapy but gives very unsatisfying results for these patients. Enormous progress in the last decade in terms of understanding the implicated genetic mutations leading to signaling and epigenetic pathway deregulation in Tfh PTCL allowed the research community to propose new therapeutic approaches. These findings point towards new biomarkers and new therapies, including hypomethylating agents, such as azacytidine, and inhibitors of the TCR-hyperactivating molecules in Tfh PTCL. Additionally, metabolic interference, inhibitors of the NF-κB and PI3K-mTOR pathways and possibly novel immunotherapies, such as antibodies and chimeric antigen receptors (CAR) directed against Tfh malignant T-cell surface markers, are discussed in this review among other new treatment options.

T-NHL subtypes and clinical perspective

Peripheral T-cell lymphomas (PTCL) are a distinct pathological entity with clinical advancements lagging behind its B-cell lymphoma counterpart. A significant proportion (15–20%) of PTCL cases are misdiagnosed as reactive or a different lymphoma subtype. An accurate diagnosis routinely requires analysis of the immunophenotype in conjunction with cellular morphology, analysis of lymph node architecture and molecular genetic analysis. Recent major advances in genomic studies examining gene expression profiling (GEP) and the genetic landscape of T-cell and NK-cell neoplasms have resulted in diagnostic, prognostic and therapeutic implications and has consequently led to revisions in the classification of PTCLs and introduction of new provisional entities. Incorporating these molecular and genetic markers, the latest 2016 WHO classification, an update of the current fourth edition, has identified 25 definitive and 6 provisional entities and further groups these lymphomas according to their usual presentation into disseminated disease (leukaemias), predominantly nodal, predominantly extra-nodal or cutaneous lymphomas. Nodal PTCLs represent the most prevalent PTCL subtype and include peripheral T-cell lymphoma - not otherwise specified (PTCL-NOS), angioimmunoblastic T-cell lymphoma (AITL), follicular T-cell lymphoma (FTCL), nodal PTCL with T follicular helper (TFH) phenotype, and systemic anaplastic large cell lymphoma (sALCL) either ALK-positive or ALK-negative. Due to better understanding of the cell of origin in T-cell lymphomas, AITL, FTCL and PTCL with TFH phenotype have been recognised as being derived from TFH cells as these neoplastic cells express at least two or three TFH cell antigens which include CD279/PD1, CD10, BCL6, CXCL13, ICOS, SAP and CCR5. In addition to the common cell of origin, these lymphomas share pathological and clinical features as well as recurrent genetic abnormalities such as mutations in TET2, IDH2, DNMT3A, RHOA and CD28, and gene fusions such as ITK-SYK and CTLA-CD28. Such features suggest that these lymphomas belong to the same spectrum of disease and are therefore now unified under a common heading. PTCL-NOS encompasses those which do not match the classification of other PTCL categories. This subtype mostly has a CD4+/CD8– phenotype and shows extreme cytological and phenotypical heterogeneity but GEP have identified at least three subgroups characterised by overexpression of GATA3, TBX21 and cytotoxic genes associated with varied clinical behaviour. Systemic ALCLs have a primarily aggressive nodal presentation and are further subdivided to ALK-positive or ALK-negative based on whether they carry the nucleoplasmin (NPM) anaplastic lymphoma kinase (ALK) translocation between chromosome 2 and 5, designated as t(2;5). We now know that a subset of ALCL, ALK-negative cases harbour rearrangement at the locus containing DUSP22 and IRF4 in chromosome 6p25, which induces down regulation of DUSP22, a dual specific phosphatase that inhibits TCR signalling. Another subset of ALK-negative ALCL has rearrangements in TP63. Clear distinction of PTCL with high CD30 expression from ALCL, ALK-negative have also been possible through GEP and as such, the former is no longer considered a provisional entity. Breast implant associated ALCL, a unique form of ALCL, ALK-negative arising in association with breast implants, is increasingly being recognised and has been included as a provisional entity. Cutaneous ALCL (cALCL), ALK-negative, the fourth subtype, is an indolent form limited to the skin. Whilst notorious to have an aggressive clinical course and an extremely poor overall prognosis, clinicians are constantly challenged with low rates of complete remissions, early relapses and failures to achieve long-term remissions despite aggressive first-line chemotherapy, in the majority of patients. More recently, improved understanding of disease biology and the molecular profile of specific PTCL subtypes has opened the door to the potential of more targeted therapies with a number of new biological therapies approved by regulatory agencies in the last few years.

Defining signatures of peripheral T-cell lymphoma with a targeted 20-marker gene expression profiling assay.

Peripheral T-cell lymphoma comprises a heterogeneous group of mature non-Hodgkin lymphomas. Their diagnosis is challenging, with up to 30% of cases remaining unclassifiable and referred to as “not otherwise specified”. We developed a reverse transcriptase-multiplex ligation-dependent probe amplification gene expression profiling assay to differentiate the main T-cell lymphoma entities and to study the heterogeneity of the “not specified” category. The test evaluates the expression of 20 genes, including 17 markers relevant to T-cell immunology and lymphoma biopathology, one Epstein-Barr virus-related transcript, and variants of RHOA (G17V) and IDH2 (R172K/T). By unsupervised hierarchical clustering, our assay accurately identified 21 of 21 ALK-positive anaplastic large cell lymphomas, 16 of 16 extranodal natural killer (NK)/T-cell lymphomas, 6 of 6 hepatosplenic T-cell lymphomas, and 13 of 13 adult T-cell leukemia/lymphomas. ALK-negative anaplastic lymphomas (n=34) segregated into one cytotoxic cluster (n=10) and one non-cytotoxic cluster expressing Th2 markers (n=24) and enriched in DUSP22-rearranged cases. The 63 TFH-derived lymphomas divided into two subgroups according to a predominant TFH (n=50) or an enrichment in Th2 (n=13) signatures. We next developed a support vector machine predictor which attributed a molecular class to 27 of 77 not specified T-cell lymphomas: 17 TFH, five cytotoxic ALK-negative anaplastic and five NK/T-cell lymphomas. Among the remaining cases, we identified two cell-of-origin subgroups corresponding to cytotoxic/Th1 (n=19) and Th2 (n=24) signatures. A reproducibility test on 40 cases yielded a 90% concordance between three independent laboratories. This study demonstrates the applicability of a simple gene expression assay for the classification of peripheral T-cell lymphomas. Its applicability to routinely-fixed samples makes it an attractive adjunct in diagnostic practice.

Canine CD4+ T-cell lymphoma identified by flow cytometry exhibits a consistent histomorphology and gene expression profile.

T-cell lymphomas (TCL) are a diverse group of neoplasms with variable diagnostic features, pathophysiologies, therapeutic responses and clinical outcomes. In dogs, TCL includes indolent and aggressive tumours such as T-zone lymphoma (TZL) and peripheral T-cell lymphoma (PTCL), respectively. Delineation of molecular subtypes and investigation into underlying pathophysiologies of aggressive TCLs remains inadequate. We investigate the correlations between flow cytometry and histopathology of 73 cases of nodal TCL. The majority of cases (82.2%) were characterized as CD4+ TCL by flow cytometry. Fewer cases were classified as CD8+ TCL (6.8%) or CD4- CD8- TCL (11.0%). All cases, regardless of immunophenotype, exhibited conserved histologic features consistent with the WHO classification of PTCL. Histologic subsets of PTCL corresponding to immunophenotypic features were not identified. Neoplastic cell size determined by flow cytometry correlated significantly with mitotic rate. RNA-seq was performed on a subset of CD4+ PTCL cases (n = 6) and compared with sorted control CD4+ T-cells. The gene expression pattern of CD4+ PTCL was similar between all cases regardless of breed. PTCL was enriched in pathways representing G-coupled protein receptor signalling, extracellular matrix remodelling and vascular development, immune signalling and mitotic activity. Furthermore, global gene expression changes were consistent with downregulation of PTEN signalling and upregulation of the MTOR-PI3K-ATK axis. In this study, we evaluated the correlations between flow cytometry, histopathology and gene expression within a large cohort of nodal TCLs. We further demonstrate the ability of flow cytometry to identify a subtype of T-cell lymphoma, CD4+ PTCL, with a uniform histomorphology and gene expression profile.

Gene Expression Profiling Using a Reverse Transcriptase-Multiplex Ligation Dependant Probe Amplification Assay Allows for an Accurate Classification of Peripheral T-Cell Lymphoma and Highlights Novel Subgroups within the PTCL-NOS Category

IntroductionVarious Peripheral T-cell lymphoma (PTCL) entities are recognized in the World Health Organization (WHO) classification based on clinical, histopathological, phenotypic and molecular criteria. Their diagnosis is however often challenging for pathologists, and up to 30% of cases, currently not classifiable, are recognized as not otherwise specified (NOS). Recent gene expression profiling (GEP) studies have significantly improved the molecular and ontogenic characterization of these tumors, but such high-throughput technologies are hardly feasible in the routine clinical setting. There is therefore an important need for alternative diagnostic strategies to allow for the development of specific therapies. Here, we sought to create a parsimonious and robust GEP assay to differentiate the different PTCL entities and to better characterize the heterogeneity of PTCL-NOS.MethodsA Reverse Transcriptase-Multiplex Ligation dependant Probe Amplification (RT-MLPA) assay addressing 20 markers was applied to a cohort of 227 PTCLs biopsies enriched in PTCL-NOS (n=126). This assay determines the expression of seventeen genes routinely tested as immunohistochemical (IHC) markers or selected from high throughput GEP studies, together with the EBV infection status (EBER1 expression) and the presence of RHOAG17V and IDH2R172K/T mutations.ResultsUnsupervised hierarchical clustering analysis of 101 control cases representing the main PTCL entities other than PTCL-NOS by RT-MLPA accurately classified 28/29 Angioimmunoblastic T-cell lymphomas (AITL), 21/21 Anaplastic large T-cell lymphomas (ALCL) ALK+, 16/16 NK/T-cell lymphomas (NKTCL), 6/6 Hepatosplenic T-cell lymphomas (HSTL) and 12/12 Adult T-cell Leukemia/Lymphomas (ATLL)(Figure). AITL were classified according to the expression of Tfh markers (CXCL13, CXCR5, ICOS, BCL6) and RHOA mutations (n=18); NKTCLs according to EBER1, GZMB and Th1 markers (TBX21, IFNγ); HSTLs to CD56, GATA3, TBX21 and BCL6; ALCL ALK+ according to CD30, ALK and cytotoxic markers (PRF, GZMB); ATLLs to ICOS and Th2 markers (GATA3, CCR4). Interestingly, ALCL ALK- cases (n=17) were divided into 2 subgroups: one, associated with high expression of CD30 and cytotoxic markers (PRF, GZMB), clustered with ALCL ALK+ cases (n=11), the other showed absence of PRF and GZMB, but expression of CD30 and Th2 markers (n=6).Applied to 126 nodal PTCL-NOS, the RT-MLPA classifier identified 33 AITL-Like cases expressing Tfh markers and often presenting with RHOA mutations (15 cases). It also identified 5 NKTCL-like cases (EBV-cytoxic) and 1 ALCL-like case (cytotoxic-CD30).The CD30-Th2 signature was found in 15 cases, reinforcing the hypothesis that it may delineate a novel PTCL entity, at the frontier between ALCL ALK- and other PTCLs. In agreement with previous GEP studies, 23 cases expressed Th2 markers but no CD30 (often in association with a significant Tfh signature, probably reflecting a contribution from the microenvironment). Twenty-five other cases showed a hybrid cytotoxic-Th1 signature. The remaining 14 cases did not reveal any recognizable gene expression profile.Finally, we observed a strong correlation between RT-MLPA and IHC for most markers evaluated by both methods (p<10-3 for CD8, CD30, GZMB, PRF, ALK, CD56, CXCL13, ICOS and GATA3), indicating that our assay is reliable and may constitute a valuable alternative to IHC.ConclusionThis study demonstrates the applicability of a parsimonious RT-MLPA classifier for the classification of PTCLs. Its simplicity of use and its applicability on FFPE samples makes it an attractive alternative to high throughput GEP approaches and IHC. Its implementation in clinical trials, in combination with conventional pathological evaluation, may thus participate to improve the classification of PTCLs and therefore the management of PTCL patients. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Follicular T-cell lymphoma: a member of an emerging family of follicular helper T-cell derived T-cell lymphomas

Unlike B-cell lymphomas, where knowledge of normal B-cell origin and differentiation has greatly contributed to their classification, the current classification of peripheral T-cell lymphomas is limited by a lack of understanding of their cellular origin. In the current World Health Organization classification of lymphomas, follicular T-cell lymphoma was formally recognized as a morphologic variant of peripheral T-cell lymphoma, not otherwise specified. There is growing evidence, however, that follicular T-cell lymphoma may be a unique clinicopathologic entity based on its morphologic features and derivation from follicular helper T-cells. In addition, there are abundant recent data supporting the concept that follicular helper T-cells can give rise to other types of T-cell lymphoma, including angioimmunoblastic T-cell lymphoma, primary cutaneous CD4+ small/medium T-cell lymphoma, and a subset of neoplasms, in addition to follicular T-cell lymphoma, currently classified as peripheral T-cell lymphoma, not otherwise specified. In this review, we focus primarily on the clinicopathologic, immunophenotypic, and molecular features of follicular T-cell lymphoma and discuss its potential relationship with other types of T-cell lymphoma thought to be derived from follicular helper T-cells.

Functional Classification of Peripheral T-Cell Lymphomas as an Approach to Improve Outcome Prediction and Therapy Selection

Many types of peripheral T-cell lymphoma (PTCL) are currently classified by the World Health Organization (WHO) based on their predominant site of organ involvement (eg, intestinal or cutaneous types). However, this approach and traditional staging scores such as the IPI can provide limited prognostic information, especially in those PTCL types where morbidity and mortality are primarily related to immune dysregulation and cytokine syndromes driven by the lymphoma cells. These "immune participatory" PTCLs (including, commonly, angioimmunoblastic T-cell lymphoma and many extranodal types) can therefore have poor outcomes even at low tumor burdens. For these reasons, a classification that includes functional profiling of the lymphoma cells may add valuable prognostic information. Such data, including cytokine expression patterns and T-cell receptor signaling pathway activation status, whether normal or abnormal, need to be considered in future classification systems, especially when incorpating targeted therapy.

Update on the World Health Organization classification of peripheral T-cell lymphomas

Peripheral T-cell lymphomas (PTCLs) are a rare and heterogeneous group of lymphoproliferative disorders of postthymic origin. Progress in elucidating the pathobiology and appropriate therapy of these neoplasms has been slow, primarily because of their rarity, but also because until the early 1990s, they were generally grouped together and combined with B-cell lymphomas. It is now understood that most PTCLs are highly aggressive and respond poorly to standard chemo therapy, and thus they have a significantly poorer prognosis than their B-cell counterparts. In 1994, the Revised European and American Lymphoma classification provided the first uniform system to classify lymphoproliferative disorders on the basis of morphology, phenotype, genetics, and clinical features. Since then, the World Health Organization (WHO) has refined this system as additional information has evolved to further elucidate the origin of these neoplasms. More recently, several new distinct and provisional categories in the updated WHO classification have been defined. This review summarizes the changes in the fourth edition of the WHO classification of lymphoid tumors, with particular focus on the aggressive subtypes.

Gene expression profiling identifies molecular subgroups among nodal peripheral T-cell lymphomas

The classification of peripheral T-cell lymphomas (PTCL) is still a matter of debate. To establish a molecular classification of PTCL, we analysed 59 primary nodal T-cell lymphomas using cDNA microarrays, including 56 PTCL and three T-lymphoblastic lymphoma (T-LBL). The expression profiles could discriminate angioimmunoblastic lymphoma, anaplastic large-cell lymphoma and T-LBL. In contrast, cases belonging to the broad category of 'PTCL, unspecified' (PTCL-U) did not share a single molecular profile. Using a multiclass predictor, we could separate PTCL-U into three molecular subgroups called U1, U2 and U3. The U1 gene expression signature included genes known to be associated with poor outcome in other tumors, such as CCND2. The U2 subgroup was associated with overexpression of genes involved in T-cell activation and apoptosis, including NFKB1 and BCL-2. The U3 subgroup was mainly defined by overexpression of genes involved in the IFN/JAK/STAT pathway. It comprised a majority of histiocyte-rich PTCL samples. Gene Ontology annotations revealed different functional profile for each subgroup. These results suggest the existence of distinct subtypes of PTCL-U with specific molecular profiles, and thus provide a basis to improve their classification and to develop new therapeutic targets.

Th1, Th2, and activated T-cell marker and clinical prognosis in peripheral T-cell lymphoma, unspecified: comparison with AILD, ALCL, lymphoblastic lymphoma, and ATLL

AbstractA new World Health Organization classification was recently proposed. However, classification of peripheral T-cell lymphomas remains to be clarified. Particularly, unspecified type was considered as a heterogeneous category. Here we studied the expressions of chemokine receptors, Th1-associated CXCR3 and CCR5 and Th2-associated marker ST2(L), and activated T-cell receptor OX40/CD134 in 185 patients with nodal T-cell lymphoma, and evaluated the relationship to prognosis. Their expression patterns correlated with the specific subtype of nodal T-cell lymphoma, such as angioimmunoblastic T-cell lymphoma (AILD), anaplastic large cell lymphoma (ALCL), and in peripheral T-cell lymphoma (PTCL), unspecified. In AILD, almost all cases were immunoreactive for OX40/CD134 (96%) and for CXCR3 (89%). In ALCL, all cases were immunonegative for OX40/CD134, and only a few cases (24%) were immunoreactive for CXCR3, whereas almost all cases (94%) were positive for ST2(L). Cases of PTCL, unspecified, were divided into 2 groups; group 1 (cases positive for either ST2(L), CCR5, or CXCR3) tended to show favorable prognosis compared with group 2 (cases negative for ST2(L), CCR5, and CXCR3). Our results indicate that further subtyping of PTCL, unspecified, into groups 1 and 2 could be significant for evaluating prognosis and understanding the functional role of these tumors.

Gamma-delta T-cell phenotype is associated with significantly decreased survival in cutaneous T-cell lymphoma

The importance of alpha beta versus gamma delta T-cell subset antigen expression in the classification of peripheral T-cell lymphomas is still unclear. The objective of this study was to investigate the prognostic value of T-cell receptor-delta 1 (TCR delta 1) expression in primary cutaneous T-cell lymphomas. TCR delta 1 cellular expression was assessed in skin biopsy specimens of 104 individuals with cutaneous T-cell lymphoma by immunohistochemistry. Both univariate (Kaplan-Meier) and multivariate (Cox regression) analyses were conducted to determine which variables (T-cell subtype, hemophagocytosis, histologic profile, age, sex, and adenopathy) were significantly associated with survival. Univariate analysis indicated that there was a statistically significant difference in survival between the patients with alpha beta cutaneous T-cell lymphoma and patients with gamma delta cutaneous T-cell lymphoma (P <.0001). There was also a statistically significant decrease in survival among patients who had subcutaneous involvement compared with patients who had epidermotropic and/or dermal involvement (P <.0001). Cox model analysis indicated that TCR delta 1 expression was the factor that was most closely associated with decreased survival (P <.0001). Among those patients with cutaneous gamma delta T-cell lymphoma (n = 33), there was a trend for decreased survival for patients who had histologic evidence of subcutaneous fat involvement in comparison with patients who had epidermotropic or dermal patterns of infiltration (P =.067). No other prognostic factors were identified as having a notable association with outcome in this subgroup. TCR delta 1 expression in primary cutaneous lymphomas is an independent prognostic factor associated with decreased survival.

New insights into peripheral T-cell lymphomas

Peripheral T-cell lymphomas comprise a morphologically diverse group of malignant lymphoproliferative disorders that arise from postthymic T cells. Currently, there exists no universally accepted system of classification of peripheral T-cell lymphoma. Recent efforts to elucidate pathogenetic mechanisms and define recognizable entities have begun to clarify the nature of these tumors. These and future studies may one day lead to a unified system of classification of peripheral T-cell lymphoma that is reproducible, biologically relevant, and more predictive of clinical behavior and prognosis.

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

Classification of peripheral T-cell lymphomas based on morphological criteria can present problems due to overlap in histological features amongst the subtypes. An immunohistochemical study was designed to study the follicular dendritic cell patterns in 21 cases of peripheral T-cell lymphoma which had been classified using the updated Kiel classification. Three patterns of distribution were observed: 1 follicular dendritic cells not detected (3 cases); 2 follicular dendritic cells restricted to remnant follicle centres (7); 3 follicular dendritic cells present as an expanded network of cells exceeding the confines of germinal centres (11). Ten out of 11 angioimmunoblastic lymphomas showed an expanded network of follicular dendritic cells. The only negative case showed features which, on review, were in keeping with a pleomorphic, medium and large cell lymphoma showing an unusual proliferation of small venules. Other than angioimmunoblastic lymphomas, only one other case showed follicular dendritic cell hyperplasia. This was an unclassified peripheral T-cell lymphoma. We conclude that follicular dendritic cell hyperplasia may be used an an aid to diagnosis of the angioimmunoblastic type of peripheral T-cell lymphoma, and we recommend the routine staining of these cells in typing of T-cell lymphomas to facilitate comparison between centres.

Recurrent chromosomal aberrations in peripheral T-cell lymphoma

Histological, immunological, and cytogenetic analysis of the same neoplastic tissues have been performed on seven patients with peripheral T-cell lymphomas (PTCL). Clonal chromosomal abnormalities in five cases are reported. The most common chromosomal aberration, observed in four patients, is a rearrangement of chromosome 14 with a breakpoint in q11.2. Aberrations of chromosome 8 also occurred in four patients, three of whom had an extra 8q. The data indicate that breakpoints of malignant diseases affecting similar cell types might cluster to specific chromosomal regions, which can be helpful in recognition and classification of PTCL.

Peripheral T-cell lymphoma. A clinicopathologic study of a morphologically diverse entity.

We analyzed the clinicopathologic features of 13 patients with immunologically confirmed peripheral T-cell lymphoma. The lymphomas were classified into poorly differentiated lymphocytic, mixed cell, and large cell types. Marked morphologic heterogeneity was noted within the mixed cell and large cell categories, and the various subtypes are described. Twelve of the 13 patients received multiagent chemotherapy. Only three of the nine patients with poorly differentiated or mixed cell lymphomas achieved a complete remission, and the median survival for this group was 11 months. In contrast, all three of the treated patients with large cell lymphomas achieved a complete remission, two of whom are alive without disease (14 and 29 months, respectively). Classification of peripheral T-cell lymphomas into lymphocytic, mixed cell, and large cell types, as well as further subclassification within the heterogeneous groups, is suggested so that pathologic features of prognostic significance can be identified.