Cutaneous lesions of angioimmunoblastic T-cell lymphoma: Clinical, pathological, and immunophenotypic features

Angioimmunoblastic T-cell lymphoma: Current Diagnostic Insights and Advances

Angioimmunoblastic T-cell lymphoma (AITL), or nodal T-follicular helper cell lymphoma, angioimmunoblastic type, is a rare and aggressive type of T-cell lymphoma characterized by a spectrum of clinical and histopathological features that can present diagnostic challenges. Derived from T-follicular helper cells, the genesis of AITL is thought to be a multistep process involving mutations in epigenetic regulatory genes such as TET2 and DNMT3A, followed by driver mutations in RHOAG17V and IDH2R172 which promote clonal expansion as well as a characteristic inflammatory milieu. This review aims to provide a comprehensive overview of AITL, including its clinical presentation, epidemiology, pathogenesis, histomorphology and treatment options. Despite advancements in the understanding of AITL biology and the development of novel treatment strategies, the prognosis for patients with AITL remains poor.

Epstein-Barr virus-related lymphoproliferative disorders of the skin

Epstein Barr Virus (EBV) is associated both solid (nasopharyngeal carcinoma, non-nasopharyngeal lymphoepithelioma-like carcinoma, gastric carcinoma, leiomyosarcoma) and hematolymphoid malignancies, some of the latter, however, spanning over a spectrum ranging from reactive and self-limiting to severe and life-threatening conditions. This review will focus on the disorder most commonly involving the skin, namely: EBV-positive mucocutaneous ulcer; lymphomatoid granulomatosis; EBV-positive diffuse large B cell lymphoma; plasmablastic lymphoma; post-transplant lymphoproliferative disorder; extranodal NK/T cell lymphoma, nasal type; angoimmunoblastic T cell lymphoma; severe mosquito bite allergy; hydroa vacciniformelike lymphoproliferative disorder. Given the uncommon occurrence of all these infiltrates in the skin, multidisciplinary approach, as well as referral to tertiary care centers are always advisable.

Angioimmunoblastic T-cell lymphoma involving the nasopharynx: An easily misdiagnosed disease with atypical histopathological features

OBJECTIVES

To explore the clinicopathologic features, treatment, and survival outcomes of angioimmunoblastic T-cell lymphoma (AITL) involving the nasopharynx.

METHODS

We retrospectively analyzed 73 cases of AITL. Among them, 64 cases with complete pre-treatment 18F-FDG positron emission tomography/computed tomography (PET/CT) images were integrated into the analysis of clinical characteristics and PET/CT findings of AITL involving the nasopharynx; 14 cases with both biopsies from lymph node and nasopharynx were included in the comparison of pathological characteristics of AITL in the two areas. Forty-six of the 73 patients who received first-line systemic treatment at our institute were included in the treatment efficacy and survival analyses.

RESULTS

Nasopharyngeal involvement was seen in 44/64 (68.8%) patients. Histologically, lymph node and nasopharyngeal biopsies in 14 patients both showed small to medium-sized tumor cells, complex inflammatory infiltration, and Reed-Sternberg-like cells or B immunoblasts. However, tumor cells with clear cytoplasm, significant high endothelial venule (HEV) hyperplasia, and perivascular infiltration were observed in 5/14, 3/14, and 2/14 nasopharyngeal biopsies, respectively, but in all fourteen lymph node biopsies (P < 0.05). Immunophenotypic profiles and gene rearrangements were highly concordant. Treatment efficacy and survival were similar between patients with nasopharyngeal involvement and those without (P > 0.05), indicating nasopharyngeal involvement is not a prognostic factor for AITL patients.

CONCLUSIONS

Nasopharyngeal involvement is common in AITL but can be easily misdiagnosed because of its atypical pathologic pattern, especially when a lymph node biopsy is unavailable. However, the patient's clinical presentation, PET/CT manifestations, the typical immunophenotype, and gene rearrangements help the diagnosis.

Deciphering the spectrum of cutaneous lymphomas expressing TFH markers

T-follicular helper (TFH) markers are expressed in the microenvironnement of marginal zone B-cell lymphoma (MZL), and in lymphomas arising from TFH-cells, sometimes making the differential diagnosis difficult. In the skin, the "TFH-spectrum" is poorly defined, going from primary cutaneous lymphoproliferative disorder with small/medium CD4+ T-cells (SMLPD) to cutaneous localizations of systemic angioimmunoblastic T-cell lymphoma (cAITL), and may pass through intermediate forms (primary cutaneous T-follicular helper derived lymphoma, not otherwise specified (PCTFHL,NOS)). We retrospectively analyzed 20 MZL, 13 SMLPD, 5 PCTFHL, and 11 cAITL clinically, histologically, and molecularly, to define tools to differentiate them. Characteristics that might favor the diagnosis of MZL over SMLPD are: multiple skin nodules (p < 0.001), nodular architecture (p < 0.01), residual germinal centers with follicular dendritic cell network (p < 0.001), monotypic plasma cells (p < 0.001), and few staining with PD1 (p = 0.016) or CXCL13 (p = 0.03). PCTFHL and cAITL presented as multiple (p < 0.01) lesions, in older patients (p < 0.01), with systemic symptoms and/or biological alterations (p < 0.01). Immunophenotypic loss of T-cell markers (p < 0.001), BCL6 (p = 0.023) and/or CD10 staining (p = 0.08), and a higher proliferative index (≥ 30%, p = 0.039) favoured these diagnoses over SMLPD. Pathogenic variants were observed by genomic sequencing in 47% of MZL (TNFAIP3 (32%), EP300 (21%), NOTCH2 (16%), KMT2D (16%), CARD11 (10.5%)), 8% of SMLPD (TET2), 40% of PCTFHL (SOCS1 (20%), ARID1A (20%)) and 64% of cAITL (TET2 (63.6%), RHOA (36.4%), NOTCH1 (9%)). This study characterizes the various clinical and histological features between cutaneous lymphomas expressing TFH markers and highlights the value of the interest of screening for genomic mutations in difficult cases.

Linear IgA bullous dermatosis in the setting of angioimmunoblastic T-cell lymphoma

We report an 80-year-old male developing linear IgA bullous dermatosis (LAD) in the setting of angioimmunoblastic T-cell lymphoma (AITL). This phenomenon is rare, as only three cases have been described in the literature. The pathophysiologic process can be attributed to dysregulation in somatic hypermutation and the expression of chemokine receptor 5 in AITL, contributing to increased IgA. Immunoglobulin production resulting from clonal plasma cell expansion may be because of the B-cell promotional effect by neoplastic follicular helper T-cells. Beyond providing a pathophysiologic platform for AITL-associated LAD, we also briefly summarized prior cases. This report demonstrates the importance of considering LAD in the differential diagnosis for patients with a bullous eruption in the setting of AITL.

Cutaneous Reactive B-cell Lymphoid Proliferations

Cutaneous lymphoid hyperplasia (CLH), also known as cutaneous pseudolymphoma, is a spectrum of benign conditions characterized by reactive B- and T-cell cutaneous lymphocytic infiltrates. B-cell lymphoid proliferations are a heterogenous group of non-neoplastic cutaneous diseases that must be histopathologically distinguished from cutaneous B-cell lymphomas. These proliferations can be observed as reactive phenomena to infections, medications, allergens, neoplasms, and more. Further, there are many inflammatory conditions that present with reactive B-cell infiltrates, including actinic prurigo, Zoon balanitis, Rosai-Dorfman, and cutaneous plasmacytosis. This review summarizes multiple cutaneous B-cell lymphoid proliferations within the major categories of reactive and disease-associated CLH. Further we discuss major discriminating features of atypical CLH and malignancy. Understanding the specific patterns of B-cell CLH is essential for the proper diagnosis and treatment of patients presenting with such lesions.

Cutaneous Involvement of Angioimmunoblastic T-Cell Lymphoma Masquerading as B-Cell Reactive Lymphoid Hyperplasia

ABSTRACT

A 59-year-old woman presented with a persistent eruption manifested as multiple agminated miliary facial papules. Histopathological examination showed prominent nodular dermal lymphoid infiltrates with hyperplastic follicles that were initially interpreted as B-cell reactive lymphoid hyperplasia. Several years later, an additional biopsy showed a dense perifollicular infiltrate with reactive primary and secondary follicles. Accompanying T cells corresponded to CD3/CD4/PD1/CXCL13-positive cells and scattered Epstein-Barr virus-positive B cells were identified by in situ hybridization. A monoclonal T-cell population was demonstrated by TCRγ and TCRβ Polymerase Chain Reaction amplification, as well as a minor abnormal circulating T-cell population by flow cytometry (0.62% of the white blood cells, CD4+CD3s-CD7-). A biopsy specimen from an enlarged right supraclavicular lymph node disclosed nodal involvement by angioimmunoblastic T-cell lymphoma. The observation of B-cell dermal nodular infiltrates with well-demarcated lymphoid aggregates forming primary lymphoid follicles may lead to overlook the T-cell component in some cases of angioimmunoblastic T-cell lymphoma. In such cases, a careful assessment of the apparently minor T-cell component is important to establish a correct diagnosis.

Lymphomatoid Papulosis With a Unique T Follicular Helper-Like Phenotype

Lymphomatoid papulosis (LyP) is a benign skin condition that typically presents with grouped or scattered lesions on the body that self-resolve within weeks or months of onset. LyP belongs to the group of CD30-positive lymphoproliferative disorders. Several histological variants of LyP exist, and the histological features of LyP can overlap with other lymphoproliferative disorders; therefore, both histological and clinical correlations are needed for a proper diagnosis of LyP. We report an unusual case of LyP displaying a T follicular helper cell-like phenotype and histopathologically resembling the primary cutaneous CD4-positive small-sized to medium-sized T-cell lymphoproliferative disorder.

How I Diagnose Angioimmunoblastic T-Cell Lymphoma

OBJECTIVES

Angioimmunoblastic T-cell lymphoma (AITL) is a subtype of peripheral T-cell lymphoma derived from T-follicular helper cells. For pathologists, diagnosing AITL may be challenging due to its wide clinical and histopathologic spectrum, which can mimic a variety of reactive and neoplastic processes.

METHODS

We summarize and discuss the clinicopathologic features of AITL, emphasizing diagnostic tools available to the practicing pathologist. Common diagnostic dilemmas are discussed.

RESULTS

AITL exhibits various histologic patterns and is often associated with a prominent microenvironment that can obscure the neoplastic cells. Atypical B-cell proliferations, which can take a number of forms, are common in AITL, and clonal B-cell expansion can be seen. The atypical B cells can closely resemble Hodgkin/Reed-Sternberg cells, leading to misdiagnosis as classic Hodgkin lymphoma. Molecular studies have revealed recurrent genetic alterations, which can aid in differential diagnosis, particularly in problematic cases.

CONCLUSIONS

Given the complex diagnostic challenges in AITL, an integrated approach, incorporating clinical, morphologic, immunophenotypic, and molecular findings, is helpful to reach an accurate diagnosis.

Clinicopathological characterization of follicular helper T-cell-derived peripheral T-cell lymphoma involving Waldeyer's ring

Follicular helper T-cell-derived peripheral T-cell lymphoma (TFH-derived PTCL) initially present in the Waldeyer's ring is a rare condition with a challenging diagnosis. This study aimed to evaluate the clinicopathological characteristics and diagnosis of Waldeyer's ring TFH-derived PTCL and raise awareness of this type of lymphoma. A series of 13 cases of Waldeyer's ring TFH-derived PTCL were retrospectively analyzed. Clinically, most patients presented with localized manifestations, such as painless cervical lymphadenopathy (7/13), pharyngalgia (6/13), and nasal obstruction (3/13), and systemic symptoms were uncommon. Macroscopically, plump mass (9/13) and nodular lesions (3/13) covered with intact and tense mucosa were the main findings on fiberoptic laryngoscopy examination. Pathologically, diffuse infiltration with atypical lymphocytes in the lamina propria (10/13) was the most common growth pattern. Clear cells (9/13) and vascular proliferation (11/13) within a polymorphic inflammatory background (11/13) were frequently observed. All cases expressed at least two TFH markers: PD-1 in 92.3% (12/13), BCL6 in 69.2% (9/13), CXCL13 in 53.8% (7/13), and CD10 in 46% (6/13). Targeted next-generation sequencing analysis identified frequent mutations, including TET2 (10/11), RHOA (6/11), DNMT3A (3/11), and IDH2 (2/11). The overall survival rate at 2 years was 35.5%, and survival analysis revealed that patients with localized disease showed better overall survival (P = 0.022). In conclusion, careful morphological observation combined with immunohistochemistry and molecular analysis would help in diagnosis of TFH-derived PTCL involving the Waldeyer's ring, which is a rare condition that frequently presents with atypical clinical manifestations.

Angioimmunoblastic T-cell lymphoma after acute myeloid leukemia: Alleged common pathogenesis. A case report and literature review

The genomic landscape of AITL is characterized by mutation of epigenetic modifiers. This gene expression pattern resembles myeloid diseases and shows a potential role for hypomethylating agents as possible therapy for AITL.

How I Diagnose Primary Cutaneous Marginal Zone Lymphoma

OBJECTIVES

Primary cutaneous marginal zone lymphoma (PCMZL) is 1 of the 3 major subtypes of primary cutaneous B-cell lymphoma. The diagnosis of PCMZL may be challenging, as the differential diagnosis includes benign cutaneous lymphoproliferations as well as other primary or secondary cutaneous B-cell or T-cell lymphomas. This review describes our approach to the diagnosis of PCMZL.

METHODS

Two cases are presented that illustrate how we diagnose each of the 2 subtypes of PCMZL. The clinicopathologic features of PCMZL and the ways in which these cases can be distinguished from both benign and other neoplastic entities are emphasized.

RESULTS

A definitive diagnosis of PCMZL requires the incorporation of histologic and immunophenotypic features, molecular genetic studies in some cases, and just as importantly, clinical findings. Emerging data suggest that the heavy chain class-switched cases may be more like a clonal chronic lymphoproliferative disorder.

CONCLUSIONS

The 2 subtypes of PCMZL create different diagnostic challenges and require the use of a multiparameter approach. Although very indolent, it is important to distinguish PCMZLs from reactive proliferations, because they frequently recur and may require antineoplastic therapies. It is also critical to distinguish PCMZLs from other B- or T-cell lymphomas so that patients are properly evaluated and not overtreated.

New preclinical models for angioimmunoblastic T-cell lymphoma: filling the GAP

Mouse models are essential to study and comprehend normal and malignant hematopoiesis. The ideal preclinical model should mimic closely the human malignancy. This means that these mice should recapitulate the clinical behavior of the human diseases such as cancer and therapeutic responses with high reproducibility. In addition, the genetic mutational status, the cell phenotype, the microenvironment of the tumor and the time until tumor development occurs, should be mimicked in a preclinical model. This has been particularly challenging for human angioimmunoblastic lymphoma (AITL), one of the most prominent forms of peripheral T-cell lymphomas. A complex network of interactions between AITL tumor cells and the various cells of the tumor microenvironment has impeded the study of AITL pathogenesis in vitro. Very recently, new mouse models that recapitulate faithfully the major features of human AITL disease have been developed. Here, we provide a summary of the pathology, the transcriptional profile and genetic and immune-phenotypic features of human AITL. In addition, we give an overview of preclinical models that recapitulate more or less faithfully human AITL characteristics and pathology. These recently engineered mouse models were essential in the evaluation of novel therapeutic agents for possible treatment of AITL, a malignancy in urgent need of new treatment options.

An Update on Molecular Biology of Cutaneous T Cell Lymphoma

Cutaneous T cell lymphomas represent a heterogenous group of lymphoproliferative disorders defined by clonal proliferation of T cells present in the skin. The latest WHO classification in 2016 and WHO-EORTC classification in 2018 has updated the classification of these entities based on the molecular profile. Research in the field of molecular genetics of CTCL has allowed a better understanding of the biology of these tumors and has helped to identify potential targets for therapy that can be tailored to individual patients. In this review, we discuss the latest developments in the molecular profile of CTCLs including biomarkers for diagnosis, prognosis, and potential therapeutic targets. We have also touched upon the utility of various molecular diagnostic modalities. For the purpose of this review, we researched papers in PubMed indexed journals in English literature published in the past 20 years using keywords CTCL, mycosis fungoides, molecular profile, molecular diagnosis, whole genome profile, genomic landscape, TCR clonality.