Cutaneous γδ T-cell lymphomas: a spectrum of presentations with overlap with other cytotoxic lymphomas. Am J Surg Pathol. 2012;36:1656-1665. [PMID: 23073324 DOI: 10.1097/pas.0b013e31826a5038]

Primary Cutaneous Gamma-Delta T-Cell Lymphoma With Long-Term Indolent Clinical Course Initially Mimicking Lupus Erythematosus Profundus

Primary Cutaneous Gamma-Delta (γδ) T-Cell Lymphoma (PCGDTCL) is a rare primary cutaneous lymphoma of aggressive nature. Only a few cases with an initially indolent course over years have been published. PCGDTCL can mimic diseases with benign behavior in their clinical and histopathological presentation, such as lupus erythematosus profundus, but also other lymphomas, for example subcutaneous panniculitis-like T-cell lymphoma. In our patient, the results of histopathological, immunofluorescence microscopy, and clinical examinations of early lesions first led to the diagnosis of lupus erythematosus profundus. Two years after this diagnosis and 6 years after the first clinical symptoms appeared, the disease progressed with erosive and ulcerating plaques and a PCGDTCL with hemophagocytic syndrome with an aggressive course was diagnosed. A distinct correlation of clinical, histopathological, immunohistochemical, and molecular-pathological examinations is needed to differentiate between the potentially malignant and benign diseases. Re-biopsies of different skin lesions in uncertain cases are strongly indicated. This case demonstrates that an indolent clinical phenotype can precede an aggressive clinical course in PCGDTCL.

A Case of Fever and Erythema Nodosum-Like Lesions Leading to a New Diagnosis of Gamma-Delta T-Cell Lymphoma Complicated by Hemophagocytic Lymphohistiocytosis

A 69-year-old Vietnamese female presented with fever and new-onset tender subcutaneous nodules on her trunk and lower extremities initially thought to be clinically consistent with erythema nodosum. A biopsy showed an atypical, predominantly lobular lymphocytic panniculitis with admixed neutrophils, karyorrhectic debris, and histiocytes with subcutaneous fat necrosis. Immunohistochemistry was consistent with gamma-delta T-cell lymphoma. The patient was initiated on a chemotherapy regimen of cyclophosphamide, doxorubicin, vincristine, etoposide, and prednisone (CHOEP) with partial remission, and is currently undergoing evaluation for bone marrow transplant. This case highlights the ability of cutaneous gamma-delta T-cell lymphoma to mimic more common cutaneous conditions such as erythema nodosum, and stresses the importance of a broad differential for new presentation of tender subcutaneous nodules with concomitant systemic symptoms.

Primary cutaneous γδ T-cell lymphoma with unusual immunophenotype: A case report and review of published work

Primary cutaneous γδ T-cell lymphoma (CGD-TCL) is a rare form of primary cutaneous lymphoma. The histopathological features of CGD-TCL are still unclear because of its rarity. Here, we report a case of a 77-year-old Japanese man who presented with a 9-month history of erythematous plaques on his left forearm. Skin biopsy specimens revealed the infiltration of atypical medium/large-sized lymphocytes from the epidermis to the deep dermis. Atypical lymphocytes were positive for CD3, CD5, CD8 and Vδ1, and negative for CD4, CD7, CD56, EBER-ISH, intracellular antigen-1, granzyme B and perforin. CD30 was partially expressed. We also reviewed 246 cases of CGD-TCL from the published work. CD4^- CD8^- double-negative cases were 113 of 196 cases (57.6%), followed by CD4^- CD8⁺ cases (52/196, 26.5%). CD5 was expressed in 25.8% of the cases (34/132). At least one cytotoxic molecule marker was expressed in 150 of 160 cases (93.8%). Some cases showed an indolent clinical course, especially in mycosis fungoides-like CGD-TCL cases. CD5 positivity and lack of cytotoxic molecule expression could be associated with a better prognosis. In addition, CD30 expression was found in approximately half of CGD-TCL cases (51/112 cases), suggesting that brentuximab vedotin could be a good treatment option for such patients. Further studies with more cases with detailed clinical and pathological information are necessary to elucidate the etiology and prognostic markers of this entity.

Peripheral T-Cell Lymphoma Arising in Patients With Chronic Lymphocytic Leukemia

OBJECTIVES

To describe three further cases of anaplastic large cell lymphoma (ALCL) occurring in patients with preexisting chronic lymphocytic leukemia (CLL). We also reviewed the literature of previously published cases.

METHODS

We discuss the clinical features, histopathology, and outcomes for three patients with ALCL and CLL from Perth, Australia. The cases were also included in a literature review of existing cases and comparisons were made with our cohort.

RESULTS

The three patients included two men (aged 77 and 74 years) and one woman (aged 66 years). All had a history of untreated CLL with diagnosis established 4 to 16 years before. They had lymphadenopathy and/or cutaneous/soft tissue lesions that proved to be ALCL, ALK+ (one case) or ALCL, ALK- (two cases).

CONCLUSIONS

Further research is required in this area to establish prognostic and management recommendations. Increasing numbers of cases are being described. Positron emission tomography with computed tomography was not useful in our cohort for diagnosing progression.

Activated-cytotoxic TCRαβ+CD4+ peripheral T-cell lymphoma with hypodermal localization: Case report of a lymphoproliferative disorder probably evolved from the CD4+ cytotoxic T-cell subpopulation

The World Health Organization (WHO) classification of hematopoietic and lymphoid tumors identifies distinctive subtypes of peripheral T-cell lymphoma (PTCL), and, additionally, some PTCLs involving mostly extranodal sites like the skin. The difficulty of classifying PTCLs according to the normal stages of T-cell differentiation and the lack of definitive diagnostic markers for most of the subtypes make the diagnosis of these diseases challenging. PTCL cases which do not fit into any of the specifically defined entities are categorized as PTCL not otherwise specified (PTCL-NOS). PTCLs-NOS represent less than 2% of the total cases of T-cell lymphoma involving the skin. This article illustrates a case of a PTCL-NOS in which tumor cells have an activated cytotoxic TCRαβ+CD3+CD4+CD56+ T-cell phenotype and histopathologic features of subcutaneous panniculitis-like T-cell lymphoma, leading to a fatal outcome.

Recent Advances in Cutaneous T-cell Lymphoma: Diagnostic and Prognostic Considerations

This review describes the latest advances in the diagnosis of cutaneous T-cell lymphoma focusing on the most clinically useful features introduced since the publication of the World Health Organization revision in 2017. Clinical entities described include mycosis fungoides, Sézary syndrome, lymphomatoid papulosis, primary cutaneous anaplastic large cell lymphoma, primary cutaneous gamma delta T-cell lymphoma, primary cutaneous acral CD8⁺ T-cell lymphoma, primary cutaneous CD4⁺ small/medium T-cell lymphoproliferative disorder, and hydroa-vacciniforme-like lymphoproliferative disorder. Distinguishing histologic clues to diagnosis are discussed, and important molecular advances are described. Key prognostic indicators that may assist clinicians with timely and appropriate management options are presented.

C-C chemokine receptor 4 expression in CD8+ cutaneous T-cell lymphomas and lymphoproliferative disorders, and its implications for diagnosis and treatment

AIMS

Patients with aggressive CD8+ cutaneous T-cell lymphomas (CTCLs) progress rapidly and respond poorly to therapy. Confounding treatment planning, there is clinicopathological overlap between aggressive CD8+ CTCLs and other lymphoproliferative disorders (LPDs). Hence, improved diagnostic methods and therapeutic options are needed. The aim of this study was to examine C-C chemokine receptor 4 (CCR4) expression as a diagnostic and therapeutic biomarker in CD8+ CTCLs/LPDs.

METHODS AND RESULTS

Forty-nine cases (41 patients) with CD8+ CTCLs/LPDs were examined, including CD8+ mycosis fungoides (MF) (n = 14), aggressive epidermotropic CD8+ cytotoxic T-cell lymphoma (AETCL) (n = 8), subcutaneous panniculitis-like T-cell lymphoma (SPTCL) (n = 7), CD30+ LPDs (n = 6), primary cutaneous γδ T-cell lymphoma (GDTCL) (n = 6), and others (n = 8). Immunohistochemical tissue staining was performed with a CCR4 monoclonal antibody on formalin-fixed paraffin-embedded tissue sections. CCR4 immunostaining was graded as percentage infiltrate, i.e. high (>25%) and low (≤25%), and the results were correlated with clinicopathological diagnoses. CCR4 expression was seen in 69% of the studied cases. Any CCR4 positivity was seen in all CD8+ MF cases, in 83% of CD30+ LPD cases, in 75% of AETCL cases, in 33% of GDTCL cases, and in none of the SPTCL cases. High CCR4 expression was seen in 79% of CD8+ MF cases versus 33% of CD30+ LPD cases, in 17% of GDTCL cases, and in 12.5% of AETCL cases. Patients with more advanced MF stage had higher CCR4 expression.

CONCLUSIONS

CCR4 immunohistochemistry may be an adjunct in distinguishing advanced CD8+ MF from other CD8+ CTCLs/LPDs. Although CCR4 expression may justify therapeutic targeting of this receptor in CD8+ MF, the role of such therapies in other CD8+ CTCLs/LPDs is not yet clear.

Overview of Cutaneous T-Cell Lymphomas

Non-Hodgkin's lymphoma (NHL) encompasses a diverse collection of systemic and primary cutaneous lymphomas. Cutaneous T-cell lymphomas (CTCLs) represent about 13% of all NHLs, which are further subdivided into a heterogeneous group with vastly different presentations and histologic features. Diagnosis requires integration of clinical, pathologic, and molecular features. Among CTCLs, mycosis fungoides and Sézary syndrome are the most prevalent. Treatment is aimed at limiting morbidity and halting disease progression. Hematopoietic stem cell transplantation is the only therapy with curative intent.

Cutaneous Lymphoproliferative Disorders: What's New in the Revised 4th Edition of the World Health Organization (WHO) Classification of Lymphoid Neoplasms

Cutaneous lymphoproliferative disorders remain a challenging aspect of dermatopathology, in part due to the rarity of the entities and extreme variability in clinical outcomes. Although many of the entities remain unchanged, the approach to some of them has changed in the new 2016 classification scheme of the World Health Organization. Chief among these are Epstein-Barr virus-associated lymphoproliferative disorders such as Epstein-Barr virus-associated mucocutaneous ulcer and hydroa vacciniforme-like lymphoproliferative disorder, primary cutaneous CD8+ aggressive epidermotropic cytotoxic T-cell lymphoma, primary cutaneous acral CD8+ T-cell lymphoma, primary cutaneous CD4+ small/medium T-cell lymphoproliferative disorder, and breast implant-associated anaplastic large cell lymphoma. In addition, translocations and gene rearrangements such as those involving the 6p25.3 locus have started to inform diagnosis and classification of anaplastic large cell lymphoma and lymphomatoid papulosis. In this review, we will examine what is new in the diagnostic toolbox of cutaneous lymphoproliferative disorders.

Cutaneous T-cell lymphomas in the revised 4th edition of World Health Organization classification of tumors of hematopoietic and lymphoid tissues (2017)

Recently, the World Health Organization published the revised 4th edition of its classification of tumors of hematopoietic and lymphoid tissues. The present paper is a concise comparative review of the main primary cutaneous T-cell hematopoietic tumors, with emphasis on their immunohistochemical profiles.

Rare T-Cell Subtypes

There are a number of rare T-cell lymphoma subtypes that may be encountered in clinical practice. In recent years, improved immunohistochemical techniques and molecular tumor profiling have permitted refinement of some of the diagnostic categories in this group, as well as the recognition of distinct conditions not previously well elucidated. In this chapter, we cover the diagnostic and clinical features of some of the more common of these conditions, including subcutaneous panniculitis-like T-cell lymphoma, cutaneous gamma-delta T-cell lymphoma, enteropathy-associated T-cell lymphoma, monomorphic epitheliotropic intestinal T-cell lymphoma, primary cutaneous CD8-positive aggressive epidermotropic cytotoxic T-cell lymphoma, CD4-positive small/medium T-cell lymphoproliferative disorder, and acral CD8-positive T-cell lymphoma. Given the rarity of these conditions, optimal treatments approaches are not always well established, not least as data from large-scale clinical trials are lacking. In this chapter, we aim to provide a summation of current thinking around best treatment, as well as highlighting some controversies in the management of these diagnoses.

Epidemiology and Pathology of T- and NK-Cell Lymphomas

PURPOSE

This review will describe and update readers on the recent changes in the 2017 WHO classification regarding peripheral T-cell lymphomas.

RECENT FINDINGS

Signficant advances in molecular studies have resulted in revisions to the classification as well as introduction to provisional entities such as breast implant-associated ALCL and nodal PTCL with T-follicular helper phenotype.

SUMMARY

Major advances in molecular and gene expression profiling has expanded our knowledge of these rare and aggressive diseases.

T-cell receptor-δ expression and γδ+ T-cell infiltrates in primary cutaneous γδ T-cell lymphoma and other cutaneous T-cell lymphoproliferative disorders

AIMS

The diagnosis of cutaneous γδ T-cell lymphoma (GDTCL) requires the identification of γδ chains of the T-cell receptor (TCR). Our aim in this study was, by using a new monoclonal antibody (mAb) against TCRδ, to evaluate TCRδ expression in formalin-fixed paraffin-embedded (FFPE) skin tissue from TCRγ+ cutaneous T-cell lymphoma (CTCL), and to assess TCRδ expression within a spectrum of other cutaneous lymphoproliferative disorders (CLPDs).

METHODS AND RESULTS

Twelve cases (10 patients) with TCRγ+ CTCL and 132 additional CLPD cases (127 patients) were examined, including mycosis fungoides (MF) (n = 60), cutaneous GDTCL (n = 15), subcutaneous panniculitis-like T-cell lymphoma (SPTCL) (n = 11), and CD30⁺ lymphoproliferative disorder (LPD) (n = 24). Clone H-41 against TCRδ was used on a Leica Bond-3 automated stainer to label FFPE slides. H-41 immunostaining was graded as percentage infiltrate: high (50-100%), moderate (10-49%), and low (0-9%). In TCRγ+ tumours, 12 of 12 (100%) patients showed TCRδ expression comparable to TCRγ expression. No (0%) TCRγ+ cases were negative for TCRδ. In all CLPDs, TCRδ expression was as follows: GDTCL, 16 of 20 cases (14 of 15 patients) high, two moderate, and two low; MF, 0 of 60 cases high, nine moderate, and 51 low; CD30⁺ LPD, one of 24 cases high, two moderate, and 21 low; and SPTCL, 0 of 11 cases (0 of 9 patients) high, two moderate, and two low. Three MF-like cases and one SPTCL-like case showed high expression; the remainder showed low expression.

CONCLUSIONS

mAb H-41 against TCRδ matches TCRγ in immunostaining FFPE tissues from GDTCL, supporting H-41 as a replacement for mAb γ3.20. TCRδ expression in our study suggests that the true occurrence of γδ+ non-GDTCL CTCL/CLPD may be lower than suggested by the recent literature.

New Therapies and Immunological Findings in Cutaneous T-Cell Lymphoma

Primary cutaneous lymphomas comprise a group of lymphatic malignancies that occur primarily in the skin. They represent the second most common form of extranodal non-Hodgkin’s lymphoma and are characterized by heterogeneous clinical, histological, immunological, and molecular features. The most common type is mycosis fungoides and its leukemic variant, Sézary syndrome. Both diseases are considered T-helper cell type 2 (Th2) diseases. Not only the tumor cells but also the tumor microenvironment can promote Th2 differentiation, which is beneficial for the tumor cells because a Th1 environment enhances antitumor immune responses. This Th2-dominant milieu also underlies the infectious susceptibility of the patients. Many components, such as tumor-associated macrophages, cancer-associated fibroblasts, and dendritic cells, as well as humoral factors, such as chemokines and cytokines, establish the tumor microenvironment and can modify tumor cell migration and proliferation. Multiagent chemotherapy often induces immunosuppression, resulting in an increased risk of serious infection and poor tolerance. Therefore, overtreatment should be avoided for these types of lymphomas. Interferons have been shown to increase the time to next treatment to a greater degree than has chemotherapy. The pathogenesis and prognosis of cutaneous T-cell lymphoma (CTCL) differ markedly among the subtypes. In some aggressive subtypes of CTCLs, such as primary cutaneous gamma/delta T-cell lymphoma and primary cutaneous CD8⁺ aggressive epidermotropic cytotoxic T-cell lymphoma, hematopoietic stem cell transplantation should be considered, whereas overtreatment should be avoided with other, favorable subtypes. Therefore, a solid understanding of the pathogenesis and immunological background of cutaneous lymphoma is required to better treat patients who are inflicted with this disease. This review summarizes the current knowledge in the field to attempt to achieve this objective.

NK/T-cell lymphoma, nasal type, γδ T-cell lymphoma, and CD8-positive epidermotropic T-cell lymphoma-clinical and histopathologic features, differential diagnosis, and treatment

The cytotoxic lymphomas of the skin constitute a heterogeneous group of rare lymphoproliferative diseases that are derived from mature T cells and natural killer (NK) cells that express cytotoxic molecules (T-cell intracellular antigen- 1, granzyme A/B, and perforin). Although frequently characterized by an aggressive course and poor prognosis, these diseases can have variable clinical behavior. This review delivers up-to-date information about the clinical presentation, histopathologic features, differential diagnosis, and therapy of extranodal NK/T-cell lymphoma, nasal type, primary cutaneous gamma delta T-cell lymphoma, and primary cutaneous CD8+ aggressive epidermotropic cytotoxic T-cell lymphoma.

Cutaneous Hematolymphoid and Histiocytic Proliferations in Children

This article focuses on cutaneous hematopoietic neoplasms that are more likely to be encountered in the pediatric age-group and includes both lymphoproliferative and histiocytic disorders. The cutaneous hematologic disorders in children have a different epidemiologic profile to what is seen during adulthood. Although mycosis fungoides is the most frequent form of cutaneous lymphoma in adults, it is very rare in children. Because lymphoblastic leukemias and lymphomas are more frequent in the pediatric setting, cutaneous leukemic infiltrates are relatively common in this age-group. Similarly, histiocytic disorders are more common in children, particularly Langerhans cell histiocytosis and juvenile xanthogranuloma. Notably, the histiocytic disorders have undergone significant modifications on their nomenclature in the basis of the molecular characteristics that are present in them. A summary of the most frequent cutaneous hematopoietic disorders in children will be discussed further in this review.

Peripheral T-Cell Lymphoma of the Submandibular Salivary Gland as an Unusual Manifestation of Richter's Syndrome: A Case Report and Literature Review

Richter's syndrome is the development of high-grade non-Hodgkin lymphoma (NHL) or Hodgkin lymphoma in patients with chronic lymphocytic leukemia (CLL)/small lymphocytic lymphoma (SLL). In most patients with Richter's syndrome, the high-grade NHL is diffuse large B-cell lymphoma. Only a small minority of CLL/SLL patients develop T-cell malignancies. Herein, we describe a 40-year-old male patient presenting with peripheral T-cell lymphoma not otherwise specified (PTCL-NOS) in the submandibular salivary gland, two years after the diagnosis of CLL/SLL. The PTCL-NOS consisted of small lymphocytes, which complicated diagnosis. Immunohistochemical, cytological, and molecular studies allowed the correct diagnosis of composite lymphoma (SLL/PTCL-NOS) of the submandibular salivary gland. The PTCL-NOS had a cytotoxic phenotype and aberrant expression of CD79a. There was no evidence to suggest that the PTCL-NOS of the submandibular salivary gland developed from an intimately associated submandibular lymph node or by PTCL-NOS dissemination. A review of the literature and presented case suppose that the PTCLs developed following CLL/SLL have the cytotoxic phenotype and can clinically mimic typical Richter's syndrome.

Managing Patients with Cutaneous B-Cell and T-Cell Lymphomas Other Than Mycosis Fungoides

Cutaneous lymphomas (CL) are a heterogeneous group of neoplasms characterized with clinical and histopathological variation, as well as overlap with benign dermatoses. Diagnosis and treatment of CLs is challenging and often requires a multidisciplinary approach. However, prognostic knowledge of these conditions and awareness of treatment options can help optimize appropriate use of available regimens, thereby improving care for patients. Here, we review the most recent literature and outline treatment themes for managing patients with cutaneous B-cell and T-cell lymphomas other than mycosis fungoides.

[Treatment of rare cutaneous T‑cell lymphoma and blastic plasmacytoid dendritic cell neoplasm]

Among the group of primary cutaneous lymphomas several subtypes have very low incidence rates. Based on the revision of the WHO classification for lymphoid neoplasms (2016), an overview of rare cutaneous T‑cell lymphoma (CTCL) subtypes is given and therapeutic approaches are detailed. The prognosis of the different subtypes is highly variable underlining the importance of adequate stage and subtype adapted treatment. In cases of indolent subtypes topical treatment, e. g. topical corticosteroids or UV phototherapy are often sufficient. For aggressive variants, early discussion of more aggressive systemic treatment options is warranted.

Epstein-Barr virus-negative extranodal "true" natural killer-cell lymphoma harbouring a KDM6A mutation

Extranodal natural killer (NK)/T-cell lymphoma, nasal type (ENKTL) is an extranodal aggressive T or NK-cell lymphoma that is characteristically associated with Epstein-Barr virus (EBV) infection and cytotoxic tissue-destructive features. Although ENKTL is described as a distinct entity according to the 2008 WHO classification, a considerable complexity is associated with the differential diagnosis of other T-cell lymphomas with respect to tumour cell origins, locations, and the presence of EBV infection, as well as molecular and cytogenetic abnormalities. Here, we report a rare case of EBV-negative ENKTL, where the absence of EBV in the true NK-lineage cells was confirmed by extensive phenotypic and genotypic analyses. Furthermore, using the next-generation sequencing approach, we identified mutations in the tumour suppressor genes KDM6A and TP53. The clinicopathological characteristics were almost similar to those of EBV-positive ENKTL, except for the absence of EBV and histologically apparent angioinvasiveness. This is the first reported ENKTL case with mutations in the KDM6A gene. KDM6A is one of the histone-modifying genes that are mutated in many human diseases including haematological cancers. Epigenetic regulation of gene expression has recently been demonstrated in ENKTL, and a similar pathway is thought to play an oncogenic role in EBV-negative ENKTL. Our report shows the extent of comprehensive examination required before making a definitive diagnosis for NK- and T-cell neoplasms and broadens the therapeutic options for potential targets.

Cutaneous Lymphomas with Cytotoxic Phenotype

Primary cutaneous cytotoxic lymphomas are T-cell or natural killer-cell lymphomas that express 1 or more cytotoxic markers. These neoplasms constitute a spectrum of diseases. In this review, an overview of clinical, morphologic, and phenotypical features of each subtype is provided. Differential diagnosis is discussed with attention to scenarios in which diagnostic difficulties are most frequently encountered.

Acute Cutaneous Necrosis: A Guide to Early Diagnosis and Treatment

Acute cutaneous necrosis is characterised by a wide range of aetiologies and is associated with significant morbidity and mortality, warranting complex considerations in management. Early recognition is imperative in diagnosis and management of sudden gangrenous changes in the skin. This review discusses major causes of cutaneous necrosis, examines the need for early assessment, and integrates techniques related to diagnosis and management. The literature, available via PubMed, on acute cutaneous necrotic syndromes was reviewed to summarise causes and synthesise appropriate treatment strategies to create a clinician’s guide in the early diagnosis and management of acute cutaneous necrosis. Highlighted in this article are key features associated with common causes of acute cutaneous necrosis: warfarin-induced skin necrosis, heparin-induced skin necrosis, calciphylaxis, pyoderma gangrenosum, embolic phenomena, purpura fulminans, brown recluse spider bite, necrotising fasciitis, ecthyma gangrenosum, antiphospholipid syndrome, hypergammaglobulinemia, and cryoglobulinemia. This review serves to increase recognition of these serious pathologies and complications, allowing for prompt diagnosis and swift limb- or life-saving management.

Primary cutaneous aggressive epidermotropic cytotoxic T-cell lymphomas: reappraisal of a provisional entity in the 2016 WHO classification of cutaneous lymphomas

Primary cutaneous CD8-positive aggressive epidermotropic T-cell lymphoma is a rare and poorly characterized variant of cutaneous lymphoma still considered a provisional entity in the latest 2016 World Health Organization Classification of Cutaneous lymphomas. We sought to better characterize and provide diagnostic and therapeutic guidance of this rare cutaneous lymphoma. Thirty-four patients with a median age of 77 years (range 19-89 years) presented primarily with extensive annular necrotic plaques or tumor lesions with frequent mucous membrane involvement. The 5-year survival was 32% with a median survival of 12 months. A subset of 17 patients had a prodrome of chronic patches prior to the development of aggressive ulcerative lesions. We identified cases with lack of CD8 or αβ T-cell receptor expression yet with similar clinical and pathological presentation. Allogeneic stem cell transplantation provided partial or complete remissions in 5/6 patients. We recommend the term primary cutaneous aggressive epidermotropic cytotoxic T-cell lymphoma as this more broad designation better describes this clinical-pathologic presentation, which allows the inclusion of cases with CD8 negative and/or αβ/γδ T-cell receptor chain double-positive or double-negative expression. We have identified early skin signs of chronic patch/plaque lesions that are often misdiagnosed as eczema, psoriasis, or mycosis fungoides. Our experience confirms the poor prognosis of this entity and highlights the inefficacy of our standard therapies with the exception of allogeneic stem cell transplantation in selected cases.

Immunophenotypic Shifts in Primary Cutaneous γδ T-Cell Lymphoma Suggest Antigenic Modulation: A Study of Sequential Biopsy Specimens

Primary cutaneous γδ T-cell lymphoma (PCGD TCL), an aggressive type of lymphoma, accounts for approximately 1% of all primary cutaneous lymphomas. We have occasionally observed changes in T-cell antigen expression (immunophenotypic [IP] shift) over time, a phenomenon that is considered rare in T-cell lymphoma including cutaneous T-cell lymphoma. Therefore, we assessed sequential biopsies of PCGD TCL for possible IP shifts of the lymphoma cells. We searched for cases of PCGD TCL with consecutive biopsies to perform a comprehensive immunohistochemical analysis of paired specimens. A median of 12 markers per case was tested. We evaluated the percentage of neoplastic lymphocytes and determined the differential expression of antigens (gain, loss, increase or decrease). We identified 9 patients with PCGD TCL with consecutive biopsies. All (100%) cases had IP shifts of at least 1 antigen, whereas overall 22 pairs of markers were shifted: gain of reactivity occurred in 7 (31.8%) and loss in 3 (13.6%); increased reactivity in 4 (18.2%) and decreased in 8 (36.4%). Molecular analysis of TCRγ showed identically sized monoclonal rearrangements between biopsy pairs in 4/4 (100%) patients. There was no correlation between IP shifts and the clinical appearance of lesions, histopathologic or cytologic features, or molecular rearrangements. IP shifts are common in PCGD TCL, occurring in all patients in this study and involving a variety of antigens. IP shifts do not seem to be linked to changes in the T-cell clone and are without obvious clinical or morphologic correlates. The occurrence of IP shifts in PCGD TCL suggests that antigen modulation may be involved in pathogenesis. IP shifts are somewhat frequent in T-cell lymphoma; however, it does not suggest a second neoplasm, and molecular studies can be used to determine clonal identity.

Uncommon Variants of T-Cell Lymphomas

Peripheral T-cell lymphomas represent 10% to 15% of non-Hodgkin lymphomas and comprise more than 20 different entities. Treatment of very rare T-cell lymphomas can be challenging because there are no large or randomized studies to guide clinical decision making, and treatment paradigms are often based on small series or imperfect data. Although a strict algorithm cannot be written with certainty, through the literature that exists and clinical experience, themes and principles of approaches do emerge that when coupled with clinical judgment allow reasonable and logical decisions.

Primary Cutaneous T-Cell Lymphomas Showing Gamma-Delta (γδ) Phenotype and Predominantly Epidermotropic Pattern are Clinicopathologically Distinct From Classic Primary Cutaneous γδ T-Cell Lymphomas

Primary cutaneous gamma-delta (γδ) T-cell lymphoma is a rare disease that typically involves the dermis and subcutis. Cases of primary cutaneous T-cell lymphomas showing γδ phenotype and predominantly epidermotropic pattern (EγδTCL) are not well defined. In this series, cases of primary cutaneous T-cell lymphomas showing γδ phenotype were reviewed and classified as predominantly epidermotropic (EγδTCL) when >75% of lymphoma cells resided in the epidermis or predominantly dermal and/or subcutaneous (DSγδTCL). Clinical, pathologic, and immunophenotypic features were compared in 27 biopsies from 13 patients of EγδTCL and 13 biopsies from 7 patients of DSγδTCL. The lymphoma cells were diffusely positive for CD3 and T-cell receptor (TCR)γ, mostly positive for granzyme B and TIA-1, variably positive for CD8, CD7, and CD30, and negative for CD4 and TCRβ. Two patients with EγδTCL had dissemination to lymph nodes and 1 to the lung; 1 patient with DSγδTCL had gastrointestinal involvement. The median survival of patients with EγδTCL was not reached, and with a median follow-up of 19.2 months, 3/13 died. In contrast, the median survival of patients with DSγδTCL was 10 months, and after a median follow-up of 15.6 months, 5/5 died (P<0.01). EγδTCL is a rare presentation of cutaneous T-cell lymphoma that can be distinguished from DSγδTCL based on the extent of epidermotropism and has a better prognosis and longer median survival than DSγδTCL. However, although EγδTCL resembles mycosis fungoides clinically and histologically, a subset of EγδTCL is more likely to behave more aggressively than typical mycosis fungoides.

Lymphoma classification update: T-cell lymphomas, Hodgkin lymphomas, and histiocytic/dendritic cell neoplasms

INTRODUCTION

Lymphomas are classified based on the normal counterpart, or cell of origin, from which they arise. Because lymphocytes have physiologic immune functions that vary both by lineage and by stage of differentiation, the classification of lymphomas arising from these normal lymphoid populations is complex. Recent genomic data have contributed additional depth to this complexity. Areas covered: Lymphoma classification follows the World Health Organization (WHO) system, which reflects international consensus and is based on pathological, genetic, and clinical factors. The present review focuses on the classification of T-cell lymphomas, Hodgkin lymphomas, and histiocytic and dendritic cell neoplasms, summarizing changes reflected in the 2016 revision to the WHO classification. These changes are critical to hematologists and other clinicians who care for patients with these disorders. Expert commentary: Lymphoma classification is a continually evolving field that needs to be responsive to new clinical, pathological, and molecular understanding of lymphoid neoplasia. Among the entities covered in this review, the 2016 revisions in the WHO classification particularly impact T-cell lymphomas, including a new umbrella category of T-follicular helper cell-derived lymphomas and evolving recognition of indolent T-cell lymphomas and lymphoproliferative disorders.

Cutaneous EBV-related lymphoproliferative disorders

This article will focus on the cutaneous lymphoproliferative disorders associated with EBV, with an emphasis on the upcoming changes in the revised 4th Edition of the WHO classification of tumors of the hematopoietic system, many of which deal with cutaneous disorders derived from NK-cells or T-cells. Extranodal NK/T-cell lymphoma usually presents in the upper aerodigestive tract, but can involve the skin secondarily. EBV-associated T- and NK-cell lymphoproliferative disorders (LPD) in the pediatric age group include the systemic diseases, chronic active EBV infection (CAEBV) and systemic EBV+ T-cell lymphoma of childhood. Hydroa vacciniforme (HV)-like LPD is a primarily cutaneous form of CAEBV and encompasses the lesions previously referred to as HV and HV-like lymphoma (HVLL). All the T/NK-cell-EBV-associated diseases occur with higher frequency in Asians, and indigenous populations from Central and South America and Mexico. Among the B-cell EBV-associated LPD two major changes have been introduced in the WHO. The previously designated EBV-positive diffuse large B-cell lymphoma (EBV-DLBCL) of the elderly, has been changed to EBV-DLBCL with 'not otherwise specified' as a modifier (NOS). A new addition to the WHO system is the more recently identified EBV+ mucocutaneous ulcer, which involves skin and mucosal-associated sites.

Primary Cutaneous Lymphomas in Children and Adolescents

Primary cutaneous lymphomas are rare in children and mostly represented by mycosis fungoides and CD30(+) lymphoproliferative disorders. Most pediatric cutaneous lymphomas have similar clinical/pathological features as their adult counterparts, particularly the T-cell subtypes. With regard to outcome, adult cutaneous mature T-cell lymphomas have a tendency to progression, while this appears to be relatively infrequent in children. The outcome of cutaneous B-cell lymphomas depends on subtype, with the B-lymphoblastic entity being associated with similar outcomes to precursor B acute lymphoblastic leukemia, while there are insufficient data on other entities. The diagnosis and treatment of these patients require a close collaboration between experienced pediatric pathologists, dermatologists, and oncologists. Prospective collection of longitudinal clinical and biological data from children with these rare lymphomas is needed to better understand their biological and clinical behavior and to ultimately discover the best therapeutic strategies.

Approach to Cutaneous Lymphoid Infiltrates: When to Consider Lymphoma?

Cutaneous lymphoid infiltrates (CLIs) are common in routine dermatopathology. However, differentiating a reactive CLI from a malignant lymphocytic infiltrate is often a significant challenge since many inflammatory dermatoses can clinically and/or histopathologically mimic cutaneous lymphomas, coined pseudolymphomas. We conducted a literature review from 1966 to July 1, 2015, at PubMed.gov using the search terms: Cutaneous lymphoma, cutaneous pseudolymphoma, cutaneous lymphoid hyperplasia, simulants/mimics/imitators of cutaneous lymphomas, and cutaneous lymphoid infiltrates. The diagnostic approach to CLIs and the most common differential imitators of lymphoma is discussed herein based on six predominant morphologic and immunophenotypic, histopathologic patterns: (1) Superficial dermal T-cell infiltrates (2) superficial and deep dermal perivascular and/or nodular natural killer/T-cell infiltrates (3) pan-dermal diffuse T-cell infiltrates (4) panniculitic T-cell infiltrates (5) small cell predominant B-cell infiltrates, and (6) large-cell predominant B-cell infiltrates. Since no single histopathological feature is sufficient to discern between a benign and a malignant CLI, the overall balance of clinical, histopathological, immunophenotypic, and molecular features should be considered carefully to establish a diagnosis. Despite advances in ancillary studies such as immunohistochemistry and molecular clonality, these studies often display specificity and sensitivity limitations. Therefore, proper clinicopathological correlation still remains the gold standard for the precise diagnosis of CLIs.

Lymphocytic panniculitis: an algorithmic approach to lymphocytes in subcutaneous tissue

The diagnosis of panniculitis is a relatively rare occurrence for many practising pathologists. The smaller subset of lymphocyte-predominant panniculitis is further complicated by the diagnostic consideration of T cell lymphoma involving the subcutaneous tissue, mimicking inflammatory causes of panniculitis. Accurate classification of the panniculitis is crucial to direct clinical management as treatment options may vary from non-medical therapy to immunosuppressive agents to aggressive chemotherapy. Many diseases show significant overlap in clinical and histological features, making the process of determining a specific diagnosis very challenging. However, with an adequate biopsy including skin and deep subcutaneous tissue, a collaborative effort between clinician and pathologist can often lead to a specific diagnosis. This review provides an algorithmic approach to the diagnosis of lymphocyte-predominant panniculitis, including entities of septal-predominant pattern panniculitis (erythema nodosum, deep necrobiosis lipoidica, morphea profunda and sclerosing panniculitis) and lobular-predominant pattern panniculitis (lupus erythematous panniculitis/lupus profundus, subcutaneous panniculitis-like T cell lymphoma, cutaneous γ-δ T cell lymphoma, Borrelia infection and cold panniculitis).

The 2016 revision of the World Health Organization classification of lymphoid neoplasms

A revision of the nearly 8-year-old World Health Organization classification of the lymphoid neoplasms and the accompanying monograph is being published. It reflects a consensus among hematopathologists, geneticists, and clinicians regarding both updates to current entities as well as the addition of a limited number of new provisional entities. The revision clarifies the diagnosis and management of lesions at the very early stages of lymphomagenesis, refines the diagnostic criteria for some entities, details the expanding genetic/molecular landscape of numerous lymphoid neoplasms and their clinical correlates, and refers to investigations leading to more targeted therapeutic strategies. The major changes are reviewed with an emphasis on the most important advances in our understanding that impact our diagnostic approach, clinical expectations, and therapeutic strategies for the lymphoid neoplasms.

Chronic reparative changes in medium-sized vessels in a case of primary cutaneous anaplastic large-cell lymphoma with angioinvasive features and cytotoxic phenotype: new histopathological findings in line with indolent clinical behavior

Angioinvasion/angiodestruction has been reported in a small subset of primary cutaneous anaplastic large-cell lymphomas (PCALCL). Recently, PCALCL with angioinvasive features and cytotoxic phenotype has been characterized as a variant associated with good clinical outcomes despite worrisome histopathologic features. We report a case of PCALCL with angioinvasive features and cytotoxic phenotype associated with reparative changes on the wall of medium-sized vessels involved by the neoplasm, including intimal fibroblastic proliferation and luminal obliteration. This vascular pattern, although previously unreported in PCALCL, is in accordance with the indolent behavior observed in this entity and provides a further link with lymphomatoid papulosis type E.

Zebras and hen's teeth: recognition and management of rare T and NK lymphomas

Although all the peripheral T-cell lymphomas are uncommon, there are some entities that are truly rare. Subtypes, such as enteropathy-associated T-cell lymphoma, hepatosplenic T-cell lymphoma, extranodal NK/T-cell lymphoma, and subcutaneous panniculitis-like T-cell lymphoma, have an approximate annual incidence in United States of <500 each. In these very rare subtypes, there is limited data to guide clinical decision-making. As such, our treatment decisions are often based on extrapolation, case series, personal experience, and biases. We summarize the existing data regarding initial management of these entities and compare how that management follows paradigms established for the more common T-cell lymphomas.

Primary cutaneous T-cell lymphomas: a review

Primary cutaneous T-cell lymphomas (CTCLs) represent a number of extranodal lymphomas arising from a malignant population of lymphocytes in the skin, with the most common type being mycosis fungoides (MF) representing half of all primary CTCLs. Despite advances in immunohistochemistry and molecular methodology, significant diagnostic challenges remain due to phenotypic overlap of primary CTCLs with several inflammatory dermatoses, secondary lymphomas, among other conditions. Clinical features such as presentation and morphology, staging, histology, immunophenotype and molecular features must be considered in detail before a diagnosis is made in order to minimise false-positive, false-negative and indeterminate diagnoses. Herein, we review primary CTCLs, including epidemiological data, a brief summary of clinical presentations, immunophenotype, molecular signatures and differential diagnoses.

Mycosis fungoides: A mimicker of benign dermatoses

Mycosis fungoides, the most common primary cutaneous lymphoma, may present with a broad spectrum of clinical features. As both clinical and dermatopathological findings in mycosis fungoides occasionally closely imitate other dermatoses, correct diagnosis may be a challenge both for clinicians as well as dermatopathologists. As a consequence, diagnosis of cutaneous lymphoma may be initially missed and, therefore, prompt and adequate therapeutic measures delayed. Hence, the purpose of our article was to give an overview of hitherto published “mimickers” of mycosis fungoides with a review of its diverse clinical features to alert the clinicians about the wide spectrum of this dissimulating disease. By integrating our own encountered atypical cases of mycosis fungoides we provide a comprehensive illustrated histological and moleculargenetic workup thereof and thereby critically revise the different available diagnostic tools of daily routine. Finally, we derive a practical algorithm to obtain the correct diagnosis even in such ambiguous cases of mycosis fungoides.

Subcutaneous panniculitis-like T-cell lymphoma: Pediatric case series demonstrating heterogeneous presentation and option for watchful waiting

Subcutaneous panniculitis-like T-cell lymphoma (SPTCL) and primary cutaneous gamma delta T-cell lymphoma (PCGD-TCL) were initially both classified as subcutaneous panniculitis-like T-cell lymphoma. In 2008, SPTCL with alpha-beta T-cell receptor subtype was separated from primary cutaneous gamma delta T-cell lymphomas (PCGD-TCL). We report four pediatric cases that demonstrate the heterogeneity of each disease and show that PCGD-TCL in children can have an indolent course, whereas SPTCL can behave aggressively. Three patients had spontaneous, durable remissions without treatment, whereas the one patient with disease progression was treated successfully. Watchful waiting may thus be appropriate for initial management of children.