The recognition and classification of lymphoproliferative disorders of the gut. Hum Pathol. 2014;45:899-916. [PMID: 24613566 DOI: 10.1016/j.humpath.2013.12.001]

ACVIM consensus statement guidelines on diagnosing and distinguishing low-grade neoplastic from inflammatory lymphocytic chronic enteropathies in cats

BACKGROUND

Lymphoplasmacytic enteritis (LPE) and low-grade intestinal T cell lymphoma (LGITL) are common diseases in older cats, but their diagnosis and differentiation remain challenging.

OBJECTIVES

To summarize the current literature on etiopathogenesis and diagnosis of LPE and LGITL in cats and provide guidance on the differentiation between LPE and LGITL in cats. To provide statements established using evidence-based approaches or where such evidence is lacking, statements based on consensus of experts in the field.

ANIMALS

None.

METHODS

A panel of 6 experts in the field (2 internists, 1 radiologist, 1 anatomic pathologist, 1 clonality expert, 1 oncologist) with the support of a human medical immunologist, was formed to assess and summarize evidence in the peer-reviewed literature and complement it with consensus recommendations.

RESULTS

Despite increasing interest on the topic for clinicians and pathologists, few prospective studies were available, and interpretation of the pertinent literature often was challenging because of the heterogeneity of the cases. Most recommendations by the panel were supported by a moderate or low level of evidence. Several understudied areas were identified, including cellular markers using immunohistochemistry, genomics, and transcriptomic studies.

CONCLUSIONS AND CLINICAL IMPORTANCE

To date, no single diagnostic criterion or known biomarker reliably differentiates inflammatory lesions from neoplastic lymphoproliferations in the intestinal tract of cats and a diagnosis currently is established by integrating all available clinical and diagnostic data. Histopathology remains the mainstay to better differentiate LPE from LGITL in cats with chronic enteropathy.

Classical Hodgkin Lymphoma Presenting as a Sigmoid Mass

Primary classical Hodgkin lymphoma (CHL) in the colon is exceedingly rare and shares many histologic features with other lymphoproliferative disorders in the gastrointestinal tract. Here we report a case of CHL forming a sigmoid mass. An elderly man with a past medical history of mantle cell lymphoma presented with constipation. Imaging revealed an ulcerated, circumferential mass in the sigmoid colon. Endoscopic biopsy of the mass showed ulcerated colonic mucosa with an underlying diffuse mixed inflammatory infiltrate admixed with Hodgkin and Reed-Sternberg cells. Immunohistochemistry was performed to characterize these cells. They were weakly positive for Pax-5, strongly positive for CD30, variably positive for CD15, and negative for CD45, CD20, CD3, and SOX-11. In situ hybridization was positive for Epstein-Barr virus (EBV) and negative for cytomegalovirus or herpes simplex virus. This immunophenotype is diagnostic for CHL in the clinical context of a large mass. It is not possible in this case to determine whether this is de novo CHL or progression from a precursor lesion like EBV-positive mucocutaneous ulcer. Since diagnosis, this patient underwent colectomy followed by chemotherapy and has remained in complete remission.

Pediatric hematolymphoid pathology in the gastrointestinal tract

Hematolymphoid processes involving the gastrointestinal tract in the pediatric and adolescent young adult (AYA) populations include processes occurring primarily within the gastrointestinal tract as well as systemic diseases with predilection for gastrointestinal involvement. Here, we present a focused review of reactive and neoplastic entities occurring in the pediatric and AYA age groups.

Update on B-cell lymphoproliferative disorders of the gastrointestinal tract

The gastrointestinal (GI) tract is home to a significant portion of the immune system, which interacts daily with the antigenic milieu of its contents. Therefore, the presence of white blood cells within the walls of the GI tract upon histologic examination is a familiar sight on GI biopsies-both in health and disease. The GI tract is the most common site of extranodal lymphomas, most of which are B-cell neoplasms. Here, we review common and uncommon B-cell neoplasms of the GI tract - extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma), mantle cell lymphoma, duodenal-type follicular lymphoma, diffuse large B-cell lymphoma, plasmablastic lymphoma, EBV-positive mucocutaneous ulcer, and post-transplant lymphoproliferative disorders - with special focus on literature published during the past five years. Along with the other articles in this edition of Seminars in Diagnostic Pathology, it is the authors' hope that this review proves to be a useful resource in the workup of the array of hematopoietic processes that can involve the GI tract.

Overview of Gastrointestinal Lymphoproliferative disorders✰

Lymphoproliferative processes which occur in the gastrointestinal tract range from benign reactive processes such as follicular hyperplasia (rectal tonsil) to high grade malignant lymphomas and histiocytic sarcoma. The WHO Classification of Tumors: Digestive System Tumors, 5th Edition was published in 2019 and shows several impactful changes as compared to the 4th Edition published in 2010. WHO Classification of Tumors of Hematopoietic and Lymphoid Tissues 2017 also included detailed changes in hematopoietic neoplasms within the gastrointestinal tract. New entities or renamed hematolymphoid lesions include monomorphic epitheliotropic intestinal T-cell lymphoma, duodenal-type follicular lymphoma, intestinal T-cell lymphoma, NOS and indolent T-cell lymphoproliferative disorder of the gastrointestinal tract. A brief overview of WHO classification of digestive tumors and WHO classification of tumors of hematopoietic and lymphoid tissue is discussed focusing on the changes in the most recent WHO texts. In depth discussions will be presented in other papers in this series.

Mantle cell lymphoma simulating inflammatory bowel disease

We report a case of colorectal involvement by a mantle cell lymphoma (MCL) that had been considered before as inflammatory bowel disease. Diagnosis of low-grade MCL can be difficult, and here we highlight the importance of thorough histopathological examination in case of supposed inflammatory bowel disease that does not react to therapy.

Clinical, pathological and molecular features of plasmablastic lymphoma arising in the gastrointestinal tract: A review and reappraisal

Plasmablastic lymphoma (PBL) is a CD20-negative large B-cell lymphoma with a plasmacytic phenotype and a dismal prognosis, which has been defined as a distinct entity only in the 2008 WHO Classification of Haematopoietic and Lymphoid Tissue and confirmed in the 2017 Edition. Current knowledge of the biological, clinical and prognostic features of PBL is mostly limited, resulting in diagnostic issues, as well as in lack of standard of care and effective therapeutic options. PBL commonly affects the oral cavity of HIV-positive individuals, however the gastrointestinal (GI) tract is the most common extraoral site, and in this location most patients are HIV-negative. In this review, we focus on the clinical, morphological and prognostic features of PBL arising in the GI tract, in order to improve knowledge on this rare, but aggressive disease.

Practical Approach to the Histologic Diagnosis of Gastrointestinal Lymphomas Through the First-line Marker Battery of CD20, CD3, CD30, and Epstein-Barr Virus-encoded RNAs

The gastrointestinal (GI) tract is a prevalent site for extranodal lymphomas. Some subtypes of GI tract lymphomas are aggressive and have dismal clinical outcomes. Therefore, prompt histopathologic detection of such types can be very important. We thus introduce a practical approach in the histopathologic diagnosis of GI lymphomas according to the revised World Health Organization (WHO) classification. When lymphocyte proliferation is found in the GI tract, a stepwise approach can help narrow down the differential diagnoses. When considering subtype incidence, macroscopic findings, and microscopic patterns, applying a first-line marker battery of CD20, CD3, CD30, and Epstein-Barr virus-encoded RNAs can effectively narrow down the top differential diagnoses at the initial step. Generally, the most common subtype among GI tract lymphomas is B-cell non-Hodgkin lymphoma identified by CD20 expression, followed by T-cell and NK-cell non-Hodgkin lymphomas identified by the CD3 expression, and some subtypes are defined by Epstein-Barr virus infection or CD30 expression. Macroscopically, lymphomas present as various gross types, such as large masses, small lesions, superficial and shallow lesions, polyp-like or polyposis-like features, or ulcer/necrosis/perforation. Microscopically, large pleomorphic cells or small to medium-sized tumor cells grow with various architectures and tumor microenvironments. Incorporation of macroscopic and microscopic features and the stepwise immunophenotyping may be a practical approach to the differential diagnosis of aggressive lymphoma, indolent/low-grade lymphoma, or benign to indolent lymphoproliferative disease. Exceptions always exist; this approach focuses on the relatively prevalent circumstances of lymphomatous lesions initially encountered in the GI tract.

American Registry of Pathology Expert Opinions: Evaluation of poorly differentiated malignant neoplasms on limited samples - Gastrointestinal mucosal biopsies

This review reflects a collaboration between the American Registry of Pathology (the publisher of the Armed Forces Institute of Pathology Fascicles) and Annals of Diagnostic Pathology. It is part of a series of expert recommendations on topics encountered in daily practice. The authors, three pathologists with expertise in gastrointestinal tract pathology and immunohistochemistry, met on 30 July 2019 tasked with developing expert recommendations for evaluating poorly differentiated and undifferentiated malignant neoplasms encountered on mucosal biopsies of the gastrointestinal tract. We focused on esophageal, gastric, small intestinal, colorectal, and anal (i.e., tubal gut) samples. When faced with diagnostic uncertainty on the initial H&E, it is best to begin by trying to assign the broad tumor class with screening markers such as pankeratin, S100 protein or SOX10, and CD20 or CD45. Once a broad tumor class is established, more specific differentiation markers can be pursued (e.g., lineage-restricted transcription factors for adenocarcinoma; p40 for squamous cell carcinoma; chromogranin A and synaptophysin or INSM1 for neuroendocrine neoplasms). Every small biopsy containing tumor should be considered a potential molecular pathology sample; cutting extra unstained slides with this testing in mind is strongly encouraged.

The clinical manifestation, survival outcome and predictive prognostic factors of 137 patients with primary gastrointestinal lymphoma (PGIL): Strobe compliant

This retrospective study aimed to investigate clinical characteristics and prognostic factors in patients with primary gastrointestinal lymphoma (PGIL) of Chinese population.From January 2001 to December 2015, 137 patients diagnosed with PGIL were recruited. The clinical features, treatment, and follow-up information were analysed.The median patient age was 62.3 years. With 18.47 months follow-up, the 2-year progress-free survival and overall survival rate was 74.9% and 75.5%, respectively. The overall response rate was 33.6%. Age≥60 years, advanced Lugano staging (≥stage IIE), elevated lactate dehydrogenase (LDH) levels, ≥2 extra-nodal involved sites, National Comprehensive Cancer Network International Prognostic Index (NCCN-IPI)≥4, Ki-67≥50% were associated with worse prognosis in univariate analysis (P < .05). By multivariate analyses, we determined that the involvement of extra-nodal involved sites was the only statistically significant poor prognostic factor in PGIL.Age, staging, LDH levels, NCCN-IPI, Ki-67 especially involvement of multiple extra-nodal sites were associated with poor overall survival of PGIL.

Lymphoproliferative Diseases of the Gut: A Survival Guide for the General Pathologist

The gastrointestinal tract is the most common extranodal site of involvement by lymphoma, with B-cell tumors outnumbering T-cell tumors by a wide margin. Diffuse large B-cell lymphoma is the most common lymphoid neoplasm involving the gastrointestinal tract; but a variety of other B- and T-cell neoplasms occur in the gastrointestinal organs, often with characteristic associations and/or manifestations. Although the diagnosis of gastrointestinal lymphomas can sometimes seem daunting to general pathologists, a knowledge of the most commonly encountered entities, in combination with a reasoned and pragmatic approach to the diagnostic workup, makes it possible to approach most cases with confidence.

Asymptomatic Multiple Lymphomatous Polyposis Identified during Staging Bidirectional Endoscopy of Mantle Cell Lymphoma

Multiple lymphomatous polyposis (MLP) as an extranodal manifestation of mantle cell lymphoma (MCL) in the gastrointestinal tract is rare and not often reported in the literature. We describe the case of a 63-year-old female with asymptomatic MLP found during staging bidirectional endoscopy of MCL. The patient presented only with dyspnea, but was found on physical exam to have diffuse lymphadenopathy, and subsequent positron emission tomography (PET) CT showed extensive lymph node adenopathy consistent with lymphoma. Excisional lymph node biopsy revealed high-risk MCL. Prior to therapy, staging bidirectional endoscopy was performed, which revealed duodenal bulb polyps and diffuse polyposis in the colon. Biopsies showed atypical lymphoid infiltrate identical to the initial excisional lymph node biopsy. The patient underwent aggressive induction therapy, chemotherapy and bone marrow transplantation. Four months later, repeat colonoscopy and biopsies showed normal mucosa, and repeat PET CT showed no evidence of systemic disease. Eight months later, the patient began having symptoms consistent with cauda equina syndrome, and she was found to have leptomeningeal recurrence of MCL. In spite of other medical treatment, the patient's MCL progressed and she passed away 3 years after the initial presentation.

Nodular lymphoid hyperplasia complicated with ileal Burkitt's lymphoma in an adult patient with selective IgA deficiency

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Burkitt's lymphoma in adults can occur on the basis of nodular lymphoid hyperplasia.

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Nodular lymphoid hyperplasia is associated with selective IgA deficiency.

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Nodular lymphoid hyperplasia associates IgA deficiency with Burkitt's lymphoma.

Introduction

Primary lymphomas of the small intestine are rare. Burkitt's lymphoma (BL) occurs sporadically in adults. Nodular lymphoid hyperplasia (NLH) is a rare disorder characterized by diffuse nodular lesions, which represent hyperplastic lymphoid follicles, and it is often associated with immunodeficiency syndromes.

Presentation of case

We present a 38-year-old male patient in a state of surgical emergency, suspected of Crohn’s disease, who had an unusual combination of NLH and BL of the proximal ileum. Furthermore, retrospectively analyzed documentation revealed selective IgA deficiency.

Discussion

Association between NLH and intestinal lymphomas in patients with immunodeficiency syndromes was indicated before. This case report supports the notion on NLH as a transition state between immunodeficiency and intestinal lymphomas.

Conclusion

This is one of the first case reports which presents the combination of NHL and BL. The awareness of the existence of this rare combination, especially in young adult males, can improve the diagnostic accuracy and the treatment management.

Clinical characteristics and prognostic factors of primary gastric lymphoma: A retrospective study with 165 cases

Primary gastric lymphoma (PGL) is the most common extranodal non-Hodgkin lymphoma. This retrospective study aimed to analyze the clinical characteristics, prognostic factors, and roles of different treatment modalities in patients with PGL.From January 2003 to November 2014, 165 patients who were diagnosed with PGL at West China Hospital were enrolled in this study. The clinical features, treatment, and follow-up information were analyzed.In this study, diffuse large B-cell lymphoma (DLBCL) (108, 65.5%) and mucosa-associated lymphoid tissue (MALT) lymphoma (52, 31.5%) were two predominant histological subtypes. One-year and 5-year overall survival (OS) rates of all patients were 95.2% and 79.5%, respectively; in whom 110 (66.7%) underwent surgery, 110 (66.7%) received chemotherapy, 12 (7.3%) received radiotherapy, and 10 (6.1%) received Helicobacter pylori eradication. And 75 patients (45.5%) were treated with at least 2 different types of therapies. Elevated lactic dehydrogenase (LDH) levels, poor performance status (PS), advanced stage, International Prognostic Index (IPI) score ≥3, conservative treatment, and high-grade histological subtype were associated with worse prognosis in univariate analysis. Cox regression analysis showed that LDH levels, PS, staging, and histological subtype were independent predictors of survival outcomes. In the DLBCL type, 5-year OS was significantly better in the surgically treated group (80.1%) than that of patients conservatively treated (49.8%) (P = 0.001). Surgical treatment had almost no impact on OS in the MALT type than conservative treatment (P = 0.597). The proportion of patients received conservative treatment increased from 4.5% in period 1 to 51.7% in period 4.High LDH levels, poor PS, advanced staging, and malignant pathological type at diagnosis are significantly associated with poor OS. Our data suggest that surgery is superior in prognosis over conservative treatment in the DLBCL type, but not in the MALT type. Recently, conservative treatment is becoming more preferred approach in patients with PGL.

Synchronous Upper and Lower Gastrointestinal Mucosa-Associated Lymphoid Tissue Lymphomas

Mucosa-associated lymphoid tissue lymphoma (MALToma) is a subtype of B-cell non-Hodgkin's lymphoma, comprising ∼17% of all gastrointestinal (GI) tract lymphomas. It is associated with chronic inflammation and autoimmunity, for example Helicobacter pylori gastritis and Sjogren's syndrome, respectively. Approximately 50% of GI MALTomas occur in the stomach, with small bowel and colonic lesions being less frequent. Synchronous upper and lower GI MALTomas occur rarely, with few cases reported. We present the case of a 73-year-old patient who presented with change in bowel habit and was found to have synchronous multifocal upper and lower GI MALTomas, which did not respond to H. pylori cure or to rituximab therapy, but did respond to a combination of surgery and chemotherapy with rituximab and bendamustine.

Mad2 overexpression is associated with high cell proliferation and reduced disease-free survival in primary gastrointestinal diffuse large B-cell lymphoma

OBJECTIVES

Primary gastrointestinal diffuse large B-cell lymphoma (PGI-DLBCL) is a rare hematological malignancy with limited results on carcinogenesis and clinical characteristics. The aims of the current study were to examine mitotic arrest deficiency protein 2 (Mad2) expressions in PGI-DLBCL, and assess its association with Ki-67 expression, Helicobacter pylori (H. pylori) infection, BCL-6 gene rearrangement, and clinicopathological variables.

METHODS

Cancer tissues from 38 PGI-DLBCL patients were examined for Mad2, Ki-67, and H. pylori expression by immunohistochemistry, using normal gastrointestinal tissues and nodal DLBCL as controls. BCL-6 gene translocation was analyzed by fluorescence in situ hybridization (FISH), and Mad2 expression status was evaluated along with clinicopathological characteristics.

RESULTS

Mad2 expression was increased in PGI-DLBCL patients when compared with controls. The expression of Mad2 was 51.55 ± 22.88% in PGI-DLBCL, which was higher than reactive lymph node (28.77 ± 10.89%) and lymphoid nodule in normal gastrointestinal tissue (26.41 ± 11.30%) (P = 0.002), while it was comparable to nodal DLBCL (57.23 ± 20.79%) (P = 0.358). Mad2 overexpression had a positive correlation with Ki-67 proliferation index (r = 0.55, P = 0.01) in PGI-DLBCL, and patients with BCL-6 gene rearrangement had lower Mad2 expression (P = 0.032) than patients with intact BCL-6, while no relation was found between Mad2 expression and H. pylori infection. PGI-DLBCL patients with higher Mad2 expression had lower estimated disease-free survival (DFS) (17.10% vs. 53.00%) (P = 0.049). However, no correlation was found between Mad2 expression levels and overall survival (OS) (P = 0.443).

CONCLUSIONS

Aberrant Mad2 expression was associated with cell proliferation and genetic instability, which may contribute to the carcinogenesis of PGI-DLBCL. Mad2 overexpression indicated a poor DFS and may be a potential biomarker for estimating prognosis for PGI-DLBCL patients.

The first report of a previously undescribed EBV-negative NK-cell lymphoma of the GI tract presenting as chronic diarrhoea with eosinophilia

A 74-year-old man presented with a 2-month history of watery diarrhoea. His complete blood count showed lymphopaenia and marked eosinophilia. Investigations for common infectious causes including Clostridium difficile toxin, stool culture, ova and parasites were negative. Endoscopy revealed extensive colitis and a CT of the abdomen identified numerous large abdominal lymph nodes suspicious for lymphoma. Multiple tissue samples were obtained; colon, mesenteric lymph node and bone marrow biopsy, as well as pleural fluid from a rapidly developing effusion, confirmed the presence of metastatic lymphoma with an immunophenotype most consistent with an aggressive variant of Epstein-Barr virus (EBV)-negative natural killer (NK)-cell lymphoma. The patient's clinical condition rapidly deteriorated and he died shortly following diagnosis. To the best of our knowledge, this is the first case report of a primary gastrointestinal EBV-negative NK-cell lymphoma, and its clinical presentation highlights the importance of a broad differential in the management of chronic diarrhoea.

Rare gastrointestinal lymphomas: The endoscopic investigation

Gastrointestinal lymphomas represent up to 10% of gastrointestinal malignancies and about one third of non-Hodgkin lymphomas. The most prominent histologies are mucosa-associated lymphoid tissue lymphoma and diffuse large B-cell lymphoma. However, the gastrointestinal tract can be the site of rarer lymphoma subtypes as a primary or secondary localization. Due to their rarity and the multifaceted histology, an endoscopic classification has not been validated yet. This review aims to analyze the endoscopic presentation of rare gastrointestinal lymphomas from disease diagnosis to follow-up, according to the involved site and lymphoma subtype. Existing, new and emerging endoscopic technologies have been examined. In particular, we investigated the diagnostic, prognostic and follow-up endoscopic features of T-cell and natural killer lymphomas, lymphomatous polyposis and mantle cell lymphoma, follicular lymphoma, plasma cell related disease, gastrointestinal lymphomas in immunodeficiency and Hodgkin’s lymphoma of the gastrointestinal tract. Contrarily to more frequent gastrointestinal lymphomas, data about rare lymphomas are mostly extracted from case series and case reports. Due to the data paucity, a synergism between gastroenterologists and hematologists is required in order to better manage the disease. Indeed, clinical and prognostic features are different from nodal and extranodal or the bone marrow (in case of plasma cell disease) counterpart. Therefore, the approach should be based on the knowledge of the peculiar behavior and natural history of disease.

Primary Esophageal Extranasal NK/T Cell Lymphoma With Biphasic Morphology: A Case Report and Literature Review

We report a case of esophageal extranasal NK/T cell lymphoma with biphasic morphologic features revealed by a deep large piecemeal biopsy. A 40-year-old man present with pharyngalgia, dysphagia, recurrent fever, and 5-kg weight loss for 8 months. Endoscopy demonstrated progressing longitudinal ulcers and mucosal bridges along the esophagus. The first and second biopsies obtained superficial mucosa with scattered bland-looking small lymphocytes. A subsequent large piecemeal snare abscission for biopsy showed atypical lymphoid cells infiltrating into the deep lamina propria and muscularis mucosae, whereas the superficial lamina propria was highly edematous with scant small lymphocytes. Immunohistochemical studies confirmed that both underlying atypical cells and superficial small lymphocytes were neoplastic, sharing an identical immunophenotype: positive for CD2, CD3, CD43, CD8, CD56, TIA-1 and granzyme B. Epstein-Barr virus-encoded small RNAs were found in both cells. The histologic findings were diagnostic of primary esophageal extranasal NK/T cell lymphoma. However, the patient developed bone marrow depression during chemotherapy and died of massive cerebral hemorrhage after the first cycle of chemotherapy. Primary esophageal extranodal NK/T cell lymphoma nasal type is extremely rare. We show the biphasic morphology of this disease, which highlights the importance of deep biopsy for accurate diagnosis.

[Extranodal lymphomas in adults in Szabolcs-Szatmár-Bereg county, Hungary. Analysis of 30 years' epidemiologic data]

INTRODUCTION

In their previous work, the authors reported 27-year' findings on the epidemiology of extranodal lymphomas in Szabolcs-Szatmár-Bereg county, Hungary. There are no other studies on this topic available in Hungary.

AIM

The aim of this study was to analyse in detail the epidemiologic data of patients with non-Hodgkin's lymphoma who were recorded in the leukaemia/lymphoma registry of Szabolcs-Szatmár-Bereg county during a 30-year period, to compare the main epidemiologic features of the extranodal and nodal forms, and compare the results with data reported in the international literature.

METHOD

Between January 1, 1983 and December 31, 2012, 1123 adult patients with newly diagnosed non-Hodgkin's lymphoma were recorded in the leukaemia/lymphoma registry of Szabolcs-Szatmár-Bereg county. Of those, 347 patients suffered from extranodal, and 776 patients from nodal form of non-Hodgkin's lymphoma. The authors compared the incidence of the extranodal and nodal forms, the age and sex distribution of patients, the ratio of B- and T-cell, as well as the indolent and aggressive forms, the geographic distribution and the association with carcinomas. In addition, they studied the occurrence of familial appearance and the localisation of extranodal forms.

RESULTS

The occurrence of non-Hodgkin's lymphomas indicated an increasing tendency in their county. This tendency was true for both the extranodal and nodal forms, but it was more remarkable in the extranodal form of lymphomas. They found no substantial difference between the main epidemiologic features of the two forms. The gastrointestinal tract was the most frequent site of presentation for extranodal lymphomas.

CONCLUSIONS

These observations are in line with data reported in the international literature. The data are essentially similar to those published in populations from Western European countries and the United States.

Pathology of T-cell lymphomas: diagnosis and biomarker discovery

T-cell lymphomas are a group of predominantly rare hematologic malignancies that tend to recapitulate different stages of T-cell development, in a similar way that B-cell lymphomas do. As opposed to B-cell lymphomas, the understanding of the biology and the classification of T-cell lymphomas are somewhat rudimentary, and numerous entities are still included as 'provisional categories' in the World Health Classification of hematolopoietic malignancies. A relevant and useful classification of these disorders have been difficult to accomplish because of the rarity nature of them, the relative lack of understanding of the molecular pathogenesis, and their morphological and immunophenotypical complexity. Overall, T-cell lymphomas represent only 15 % of all non-Hodgkin lymphomas. This review is focused on addressing the current status of the categories of mature T-cell leukemias and lymphomas (nodal and extranodal) using an approach that incorporates histopathology, immunophenotype, and molecular understanding of the nature of these disorders, using the same philosophy of the most recent revised WHO classification of hematopoietic malignancies.