ALK-Positive Lymphoma: A Single Disease With a Broad Spectrum of Morphology

Meningeal null cell lymphoma causing diffuse pachymeningeal contrast enhancement in a dog

Diffuse pachymeningeal contrast enhancement is an uncommon imaging finding in dogs and current understanding of its aetiologies in veterinary medicine is limited. A 2-year-old female neutered Pug presented with chronic progressive vestibular signs, facial nerve paralysis, obtundation and episodic decerebellate rigidity. A magnetic resonance imaging study of the head revealed diffuse pachymeningeal thickening and contrast enhancement involving the caudal fossa and falx cerebri. Cerebrospinal fluid analysis revealed marked neutrophilic pleocytosis. Infectious disease testing was negative and a tentative diagnosis of intracranial idiopathic hypertrophic pachymeningitis was made. Immunosuppressive treatment resulted in a short period of clinical improvement. The patient subsequently suffered multiple relapses which failed to respond to alternative immunosuppressive strategies, necessitating euthanasia. Histopathological findings supported a meningeal null cell lymphoma. While rare, neoplastic causes of diffuse pachymeningeal thickening and contrast enhancement should be considered.

Clinicopathologic features of primary central nervous system anaplastic large cell lymphoma: a multicenter study identifies age and ALK status as prognostic factors

Anaplastic large cell lymphoma with primary presentation in, and disease limited to, the central nervous system (primary CNS ALCL) is a rare and aggressive lymphoma found in a sensitive anatomic site. We report the clinical and pathologic characteristics of 17 primary CNS ALCL cases that are newly reported from six academic medical centers. We are investigating the characteristics of these cases, alongside their commonalities and differences from systemic ALCL arising at conventional anatomic sites. Clinical, pathologic, and outcome data were extracted by medical record review. The median patient age was 32 years with a male-to-female ratio of 2.4:1. Cases presented with either localized or multifocal central nervous system (CNS) disease without coinciding systemic disease. Histologically, the common pattern prevailed, and loss of pan-T-cell markers was frequent. There was a similar proportion of anaplastic lymphoma kinase (ALK) positivity in primary CNS ALCL (12/17, 71%) compared to that reported in systemic ALCL (70-80%). Our data indicate a 5-year overall survival (OS) rate of 65% and a 5-year progression-free survival (PFS) rate of 48%. Five patient deaths occurred in this study of which all were in the ALK-negative group, and all were patients over 40 years old. ALK-positive patients were significantly younger than ALK-negative patients, and survival analyses showed that both ALK-positive and younger age (≤ 40 years) were favorable prognostic factors. This is the largest series of primary CNS ALCL reported to date, which demonstrates a high proportion of ALK-positive cases and favorable outcomes for both younger and ALK-positive patients despite the involvement of a sensitive anatomic site.

Anaplastic Large-cell Lymphoma in Children: State of the Art in 2023

Anaplastic large-cell lymphoma is a rare disease and account for approximately 10% to 15% of pediatric non-Hodgkin lymphomas. They are characterized by extended stages, a high frequency of B signs and extra nodal involvement. Multiagent chemotherapy cures ∽60% to 75% of patients and relapse occurs in 35% of cases. For relapsed patients, various treatments ranging from vinblastine monotherapy to therapeutic intensification with hematopoietic stem cell transplantation have been evaluated, but there is currently no consensus on the optimal therapeutic strategy. New therapeutic perspectives are being evaluated for relapses and refractory forms as well as high-risk forms including monoclonal antibodies (Anti CD30), ALK inhibitors, and CART cells.

Variant ALK-fusion positive anaplastic large cell lymphoma (ALCL): A population-based paediatric study of the NHL-BFM study group

Frequency, distribution and prognostic meaning of ALK-partner genes other than NPM1 in ALK-positive anaplastic large-cell lymphoma (ALCL) are unknown. Forty-nine of 316 ALCL diagnosed in the NHL-BFM study group showed no nuclear ALK expression suggestive of a variant ALK-partner; 41 were analysed by genomic capture high-throughput sequencing or specific RT-PCRs. NPM1::ALK was detected in 13 cases. Among the 28 patients with a non-NPM1::ALK-fusion partner, ATIC (n = 8; 29%) and TPM3 (n = 9; 32%) were the most common. Five of eight patients with ATIC::ALK-positive ALCL relapsed, none of nine with TPM3::ALK. Variant ALK-partners are rare and potentially associated with different prognoses.

A genetic profiling guideline to support diagnosis and clinical management of lymphomas

The new lymphoma classifications (International Consensus Classification of Mature Lymphoid Neoplasms, and 5th World Health Organization Classification of Lymphoid Neoplasms) include genetics as an integral part of lymphoma diagnosis, allowing better lymphoma subclassification, patient risk stratification, and prediction of treatment response. Lymphomas are characterized by very few recurrent and disease-specific mutations, and most entities have a heterogenous genetic landscape with a long tail of recurrently mutated genes. Most of these occur at low frequencies, reflecting the clinical heterogeneity of lymphomas. Multiple studies have identified genetic markers that improve diagnostics and prognostication, and next-generation sequencing is becoming an essential tool in the clinical laboratory. This review provides a "next-generation sequencing" guide for lymphomas. It discusses the genetic alterations of the most frequent mature lymphoma entities with diagnostic, prognostic, and predictive potential and proposes targeted sequencing panels to detect mutations and copy-number alterations for B- and NK/T-cell lymphomas.

New clinical trial design in precision medicine: discovery, development and direction

In the era of precision medicine, it has been increasingly recognized that individuals with a certain disease are complex and different from each other. Due to the underestimation of the significant heterogeneity across participants in traditional "one-size-fits-all" trials, patient-centered trials that could provide optimal therapy customization to individuals with specific biomarkers were developed including the basket, umbrella, and platform trial designs under the master protocol framework. In recent years, the successive FDA approval of indications based on biomarker-guided master protocol designs has demonstrated that these new clinical trials are ushering in tremendous opportunities. Despite the rapid increase in the number of basket, umbrella, and platform trials, the current clinical and research understanding of these new trial designs, as compared with traditional trial designs, remains limited. The majority of the research focuses on methodologies, and there is a lack of in-depth insight concerning the underlying biological logic of these new clinical trial designs. Therefore, we provide this comprehensive review of the discovery and development of basket, umbrella, and platform trials and their underlying logic from the perspective of precision medicine. Meanwhile, we discuss future directions on the potential development of these new clinical design in view of the "Precision Pro", "Dynamic Precision", and "Intelligent Precision". This review would assist trial-related researchers to enhance the innovation and feasibility of clinical trial designs by expounding the underlying logic, which be essential to accelerate the progression of precision medicine.

Liquid biopsy in T-cell lymphoma: biomarker detection techniques and clinical application

T-cell lymphoma is a highly invasive tumor with significant heterogeneity. Invasive tissue biopsy is the gold standard for acquiring molecular data and categorizing lymphoma patients into genetic subtypes. However, surgical intervention is unfeasible for patients who are critically ill, have unresectable tumors, or demonstrate low compliance, making tissue biopsies inaccessible to these patients. A critical need for a minimally invasive approach in T-cell lymphoma is evident, particularly in the areas of early diagnosis, prognostic monitoring, treatment response, and drug resistance. Therefore, the clinical application of liquid biopsy techniques has gained significant attention in T-cell lymphoma. Moreover, liquid biopsy requires fewer samples, exhibits good reproducibility, and enables real-time monitoring at molecular levels, thereby facilitating personalized health care. In this review, we provide a comprehensive overview of the current liquid biopsy biomarkers used for T-cell lymphoma, focusing on circulating cell-free DNA (cfDNA), circulating tumor DNA (ctDNA), circulating tumor cells (CTCs), Epstein-Barr virus (EBV) DNA, antibodies, and cytokines. Additionally, we discuss their clinical application, detection methodologies, ongoing clinical trials, and the challenges faced in the field of liquid biopsy.

Immune Checkpoints and Their Inhibition in T-Cell Lymphomas

T-cell lymphomas (TCLs) are a rare and heterogeneous subgroup of non-Hodgkin lymphomas (NHLs), forming only 10 % of all NHL cases in Western countries. Resulting from their low incidence and heterogeneity, the current treatment outcome is generally unfavorable, with limited availability of novel therapeutic approaches. Therefore, the recent success of immune checkpoint inhibitors (ICIs) in cancer treatment motivated their clinical investigation in TCLs as well. Multiple studies showed promising results; however, cases of TCL hyperprogression following ICI treatment and secondary T-cell-derived malignancies associated with ICI treatment of other cancer types were also reported. In our review, we first briefly summarize classification of T-cell-derived malignancies, general anti-tumor immune response, immune evasion, and immune checkpoint signaling. Next, we provide an overview of immune checkpoint molecule deregulation in TCLs, summarize available studies of ICIs in TCLs, and review the above-mentioned safety concerns associa-ted with ICI treatment and T-cell-derived malignancies. Despite initial promising results, further studies are necessary to define the most suitable clinical applications and ICI therapeutic combinations with other novel treatment approaches within TCL treatment. ICIs, and their combinations, might hopefully bring the long awaited improvement for the treatment of T-cell-derived malignancies.

Uncommon spinal involvement of ALK-positive anaplastic large cell lymphoma: A pediatric case report and literature review

Anaplastic large cell lymphoma (ALCL) is a rare variety of non-Hodgkin lymphoma that primarily affects children and young adults and is caused by the fusion of the nucleophosmin 1 and ALK genes, which turns on several signalling pathways. Despite the fact that ALCL frequently affects lymph nodes and extranodal sites, involvement of the central nervous system (CNS) is quite uncommon, with symptoms like pain and fever. The spinal localization may result in neurological impairments. T1WI hypointense lesions with T2WI hyperintensity can be observed on MR images, while bone sequestra can be seen in CT scans. The gold standard for diagnosis is still histology, though. Based on distinctive morphological characteristics, immunohistochemical staining can differentiate ALK-positive ALCL from other ALCLs. The prognosis for ALK-positive ALCL is typically better than ALK-negative ALCL, and treatment options include surgery followed by chemotherapy. ALK inhibitors and CAR-T cell therapy are 2 newly developed targeted treatments that have the potential to improve results. This case report illustrates the rarity of CNS ALCL and the difficulties in diagnosis and treatment by describing a 16-year-old female patient with ALCL affecting the thoracic spine and spreading to the mediastinum and surrounding tissue.

Aggressive non-Hodgkin lymphoma in the pediatric and young adult population; diagnostic and molecular pearls of wisdom

Mature non-Hodgkin lymphomas (NHLs) of the pediatric and young adults(PYA), including Burkitt lymphoma (BL), diffuse large B cell lymphoma (DLBCL), high-grade B cell lymphoma (HGBCL), primary mediastinal large B cell lymphoma (PMBL) and anaplastic large cell lymphoma (ALCL), generally have excellent prognosis compared to the adult population. BL, DLBCL and HGBCL are usually of germinal center (GCB) origin in the PYA population. PMBL neither belongs to the GCB nor the activated B cell subtype and is associated with a poorer outcome than BL or DLBCL of comparable stage. Anaplastic large cell lymphoma is the most frequent peripheral T cell lymphoma occurring in the PYA and accounts for 10-15% of childhood NHL. Most pediatric ALCL, unlike in the adult, demonstrate expression of anaplastic lymphoma kinase (ALK). In recent years, the understanding of the biology and molecular features of these aggressive lymphomas has increased tremendously. This has led to reclassification of newer PYA entities including Burkitt-like lymphoma with 11q aberration. In this review, we will discuss the current progress discovered in frequently encountered aggressive NHLs in the PYA, highlighting the clinical, pathologic and molecular features that aid in the diagnosis of these aggressive lymphomas. We will be updating the new concepts and terminologies used in the new classification systems.

Primary Cutaneous Anaplastic Large Cell Lymphoma-A Review of Clinical, Morphological, Immunohistochemical, and Molecular Features

Primary cutaneous anaplastic large cell lymphoma (ALCL) is the second most common cutaneous T-cell lymphoma after mycosis fungoides and belongs to the spectrum of cutaneous CD30+ T-cell lymphoproliferative disorders. Although primary cutaneous ALCL usually presents as a localized nodule or papule with or without ulceration, multifocal lesions may occur in up to 20% of cases. Histologically, primary cutaneous ALCL consists of a diffuse dermal infiltrate of medium to large anaplastic/pleomorphic cells with abundant amphophilic-to-eosinophilic cytoplasm, horseshoe-shaped nuclei, strong and diffuse expression of CD30, and with focal or no epidermotropism. The neoplastic infiltrate may show angiocentric distribution and may extend to the subcutis. Patients with localized or multifocal disease have a similar prognosis with a 10-year overall survival rate of 90%. Approximately 30% of primary cutaneous ALCLs harbor a DUSP22 (6p25.3) gene rearrangement that results in decreased expression of this dual-specific phosphatase, decreased STAT3 activation, and decreased activity of immune and autoimmune-mediated mechanisms regulated by T-cells.

Transformation of recurrent ALK-positive anaplastic large-cell lymphoma from common pattern to composite pattern (lymphohistiocytic and small-cell pattern) with a change in CD30 expression

ALK-positive anaplastic large-cell lymphoma (ALK + ALCL) is characterized by expression of ALK and CD30. The current World Health Organization (WHO) classification recognizes five morphologic patterns: common, small-cell, lymphohistiocytic, Hodgkin-like, and composite. There are few reports about the morphologic transformation of ALK + ALCL. Today, we report an intriguing case of presumed transformation from common-pattern to composite-pattern (lymphohistiocytic and small-cell pattern) ALK + ALCL, with CD30 expression changing from positive to negative. This case expands understanding of morphologic transformation between different subtypes of ALK + ALCL and highlights common diagnostic pitfalls, including atypical morphology and negative CD30. Morphologic transformation of ALK + ALCL should be assigned importance, and comprehensive clinical history, histologic and immunophenotypic evaluation are vital to rendering the correct diagnosis of ALK + ALCL.

Classification and diagnostic evaluation of nodal T- and NK-cell lymphomas

Nodal T- and NK-cell lymphomas are among the most frequent T-cell malignancies and most subtypes have aggressive clinical behavior. Evolving understanding of the biology and molecular characteristics of these lymphomas, as well as the development of new precision therapy approaches, underscores the importance of ongoing updates to the classification and diagnostic evaluation of this group of malignancies. Here, we discuss the classification of nodal T- and NK-cell lymphomas based on the 2022 International Consensus Classification of Mature Lymphoid Neoplasms (2022 ICC). Lymphomas of T-follicular helper cell origin are now grouped into a single entity, follicular helper T-cell lymphoma (TFH lymphoma), with three subtypes (angioimmunoblastic-type, follicular-type, and not otherwise specified), reflecting their common cellular origin and shared molecular and clinical characteristics. Classification of anaplastic large cell lymphoma (ALCL) remains essentially unchanged; DUSP22-rearranged cases are now considered a genetic subtype of ALK-negative ALCL. Primary nodal EBV-positive T-/NK-cell lymphoma is introduced as a new provisional entity; these cases were previously considered a variant of peripheral T-cell lymphoma, not otherwise specified (PTCL, NOS). PTCL, NOS remains a diagnosis of exclusion, with evolving molecular data indicating the presence of distinct subgroups, including PTCL-TBX21, PTCL-GATA3, and EBV-negative cytotoxic PTCLs. We also discuss diagnostic strategies to facilitate the 2022 ICC classification among nodal T- and NK-cell lymphomas and the distinction from nodal involvement by extranodal neoplasms.

Genomic profiling for clinical decision making in lymphoid neoplasms

With the introduction of large-scale molecular profiling methods and high-throughput sequencing technologies, the genomic features of most lymphoid neoplasms have been characterized at an unprecedented scale. Although the principles for the classification and diagnosis of these disorders, founded on a multidimensional definition of disease entities, have been consolidated over the past 25 years, novel genomic data have markedly enhanced our understanding of lymphomagenesis and enriched the description of disease entities at the molecular level. Yet, the current diagnosis of lymphoid tumors is largely based on morphological assessment and immunophenotyping, with only few entities being defined by genomic criteria. This paper, which accompanies the International Consensus Classification of mature lymphoid neoplasms, will address how established assays and newly developed technologies for molecular testing already complement clinical diagnoses and provide a novel lens on disease classification. More specifically, their contributions to diagnosis refinement, risk stratification, and therapy prediction will be considered for the main categories of lymphoid neoplasms. The potential of whole-genome sequencing, circulating tumor DNA analyses, single-cell analyses, and epigenetic profiling will be discussed because these will likely become important future tools for implementing precision medicine approaches in clinical decision making for patients with lymphoid malignancies.

Pathological and Molecular Features of Nodal Peripheral T-Cell Lymphomas

Peripheral T-cell lymphomas (PTCLs) are uncommon neoplasms derived from mature T cells or NK cells. PTCLs comprise numerous disease entities, with over 30 distinct entities listed in the latest WHO classification. They predominantly affect adults and elderly people and usually exhibit an aggressive clinical course with poor prognosis. According to their presentation, PTCLs can be divided into nodal, extranodal or cutaneous, and leukemic types. The most frequent primary sites of PTCLs are lymph nodes, with over half of cases showing nodal presentation. Nodal PTCLs include ALK-positive and ALK-negative anaplastic large cell lymphoma; nodal T-cell lymphoma with T follicular helper cell origin; and PTCL, not otherwise specified. Adult T-cell leukemia/lymphoma also frequently affects lymph nodes. Recent pathological and molecular findings in nodal PTCLs have profoundly advanced the identification of tumor signatures and the refinement of the classification. Therefore, the therapies and pathological diagnosis of nodal PTCLs are continually evolving. This paper aims to provide a summary and update of the pathological and molecular features of nodal PTCLs, which will be helpful for diagnostic practice.

The 5th edition of the World Health Organization Classification of Haematolymphoid Tumours: Lymphoid Neoplasms

We herein present an overview of the upcoming 5^th edition of the World Health Organization Classification of Haematolymphoid Tumours focussing on lymphoid neoplasms. Myeloid and histiocytic neoplasms will be presented in a separate accompanying article. Besides listing the entities of the classification, we highlight and explain changes from the revised 4^th edition. These include reorganization of entities by a hierarchical system as is adopted throughout the 5^th edition of the WHO classification of tumours of all organ systems, modification of nomenclature for some entities, revision of diagnostic criteria or subtypes, deletion of certain entities, and introduction of new entities, as well as inclusion of tumour-like lesions, mesenchymal lesions specific to lymph node and spleen, and germline predisposition syndromes associated with the lymphoid neoplasms.

Management of Aggressive Non-Hodgkin Lymphomas in the Pediatric, Adolescent, and Young Adult Population: An Adult vs. Pediatric Perspective

Non-Hodgkin lymphoma (NHL) is a broad entity which comprises a number of different types of lymphomatous malignancies. In the pediatric and adolescent population, the type and prognosis of NHL varies by age and gender. In comparison to adults, pediatric and adolescent patients generally have better outcomes following treatment for primary NHL. However, relapsed/refractory (R/R) disease is associated with poorer outcomes in many types of NHL such as diffuse large B cell lymphoma and Burkitt lymphoma. Newer therapies have been approved in the use of primary NHL in the pediatric and adolescent population such as Rituximab and other therapies such as chimeric antigen receptor T-cell (CAR T-cell) therapy are under investigation for the treatment of R/R NHL. In this review, we feature the characteristics, diagnosis, and treatments of the most common NHLs in the pediatric and adolescent population and also highlight the differences that exist between pediatric and adult disease. We then detail the areas of treatment advances such as immunotherapy with CAR T-cells, brentuximab vedotin, and blinatumomab as well as cell cycle inhibitors and describe areas where further research is needed. The aim of this review is to juxtapose established research regarding pediatric and adolescent NHL with recent advancements as well as highlight treatment gaps where more investigation is needed.

Nuclear ingression of cytoplasmic bodies accompanies a boost in autophagy

We describe a fully new remodeling event of the nuclear envelope surrounding the nucleolus: it partitions into its regular contact with the vacuole and a dramatic internalization of globular cytoplasmic portions within the nucleus.

Membrane contact sites are functional nodes at which organelles reorganize metabolic pathways and adapt to changing cues. In Saccharomyces cerevisiae, the nuclear envelope subdomain surrounding the nucleolus, very plastic and prone to expansion, can establish contacts with the vacuole and be remodeled in response to various metabolic stresses. While using genotoxins with unrelated purposes, we serendipitously discovered a fully new remodeling event at this nuclear subdomain: the nuclear envelope partitions into its regular contact with the vacuole and a dramatic internalization within the nucleus. This leads to the nuclear engulfment of a globular, cytoplasmic portion. In spite of how we discovered it, the phenomenon is likely DNA damage-independent. We define lipids supporting negative curvature, such as phosphatidic acid and sterols, as bona fide drivers of this event. Mechanistically, we suggest that the engulfment of the cytoplasm triggers a suction phenomenon that enhances the docking of proton pump-containing vesicles with the vacuolar membrane, which we show matches a boost in autophagy. Thus, our findings unveil an unprecedented remodeling of the nucleolus-surrounding membranes with impact on metabolic adaptation.

Too Sensitive or Just Right?

OBJECTIVES

To compare the performance of the rabbit monoclonal antihuman CD246 antibody (D5F3 clone) with the established ALK1 clone for immunohistochemical assessment of anaplastic large cell lymphoma (ALCL).

METHODS

Archival cases of ALCL (n = 27) were assessed immunohistochemically by use of ALK1 and D5F3 clones under standard Clinical Laboratory Improvement Amendments-compliant conditions. The intensity of cytoplasmic staining (0 = none; 1 = faint; 2 = moderate; 3+ = strong) and proportion of neoplastic cells (0%, <5%, 5%-50%, >50%) were evaluated and compared with clinical ALK break-apart fluorescence in situ hybridization (FISH) assays.

RESULTS

Nine ALCL specimens were positive for ALK expression by ALK1 staining (33%; 1 = 1+; 0 = 2+; 8 = 3+), while 14 were positive by D5F3 staining (48%; 3 = 1+; 1 = 2+; 10 = 3+). Across the cohort, D5F3 staining showed a significantly greater proportion of cells staining positive (P = .02) and greater intensity (P = .03). Of 3 cases positive for D5F3 only with FISH results, none showed rearrangements, although 1 showed copy number gains at the ALK locus in a subset of cells.

CONCLUSIONS

Overall, D5F3 showed greater stain intensity and proportion staining than ALK1 in ALK-positive ALCL cases, which is especially helpful in limited samples. Caution and consideration of orthogonal ALK testing types is recommended, especially for cases with weak or focal staining.

Primary Central Nervous System Anaplastic Large Cell Lymphoma, ALK Positive

OBJECTIVES

Primary central nervous system anaplastic large cell lymphoma, anaplastic lymphoma kinase positive (primary CNS ALCL, ALK+) is a rare CNS lymphoma whose description is limited to case reports. These tumors have a variable clinical course, and prognosis is primarily determined by age. We present the largest case series to date of primary CNS ALCL, ALK+, with observational data.

METHODS

A retrospective search of multiple academic centers was performed to identify cases of primary CNS ALCL, ALK+. We also performed a review of published cases of primary CNS ALCL, ALK+. Clinical history, radiography, pathology, and genetic testing data were obtained to determine the prognostic implications in the context of clinical course.

RESULTS

We identified three cases of primary CNS ALCL, ALK+ from our databases. A literature review identified 30 published reports of 31 individual cases. Clinical features for the combined 34 cases included a median age of 18.5 years, with a male to female ratio of 4.7:1, and the most common symptom was headache. Genetic studies demonstrated an ALK rearrangement by fluorescence in situ hybridization, and a gene fusion assay confirmed an NPM1-ALK gene fusion in one case.

CONCLUSIONS

We present the largest case series to date of a rare primary CNS lymphoma with additional diagnostic and clinical information.

Small cell/lymphohistiocytic morphology is associated with peripheral blood involvement, CD8 positivity and retained T-cell antigens, but not outcome in adults with ALK+ anaplastic large cell lymphoma

Several morphologic variants of ALK+ anaplastic large cell lymphoma (ALCL) are recognized. The small cell (SC) and lymphohistiocytic (LH) variants are reported to be associated with poorer outcome in children with ALK + ALCL. In this study of 102 adults with ALK + ALCL, there were 18 (18%) cases of SC and/or LH variants. Patients with SC/LH ALK + ALCL more often had peripheral blood involvement than patients with non-SC/LH neoplasms (60% vs 0%, p = 0.02). There were no other significant differences in clinical features between patients with SC/LH versus non-SC/LH ALK + ALCL. Compared with non-SC/LH cases of ALK + ALCL, neoplasms with SC/LH features were more often positive for CD2 (92% vs. 36%, p = 0.0007), CD3 (81% vs. 15%, p = 0.0001), CD7 (80% vs. 37%, p = 0.03), and CD8 (54% vs. 7%, p = 0.0006). There were no other significant differences in the immunophenotype between SC/LH and non-SC/LH ALK + ALCL cases. The initial chemotherapy regimens and the response rates were similar between patients with ALK + ALCL with SC/LH patterns versus those with non-SC/LH patterns. After a median follow-up of 30.8 months (range, 0.3-208 months), patients with high (>3) International Prognostic Index (IPI) scores had significantly shorter overall survival than patients with low (<3) IPI scores (p = 0.003). However, there was no significant difference in overall or progression-free survival between patients with SC/LH versus non-SC/LH ALK + ALCL (p = 0.99 and p = 0.94, respectively). We conclude that, in adults with ALK + ALCL, SC and LH variants are associated with peripheral blood involvement and a CD8 + immunophenotype with retention of T-cell markers (CD2, CD3, and CD7). However, in contrast with children with ALK + ALCL, SC and LH variants appear to have no impact on prognosis in adults with ALK + ALCL.

Lymphoma versus Carcinoma and Other Collaborations

David Mason started his research career at a time when lymphoma diagnosis was based primarily on cellular morphology, clinical symptoms and special cytochemical stains using formalin fixed tissue sections. There were occasions, however, where the morphology was unhelpful, such as in the case of anaplastic or poorly differentiated tumours, where a distinction between lymphoma and a non-haematopoietic tumour was often problematical. Accurate diagnosis became even more important with the developments in the clinical staging of lymphoma and the availability of more effective treatments. One way forward to improve diagnosis was to use immunohistochemistry to study the antigens expressed by the tumor cells.

Central nervous system ALK-negative anaplastic large cell lymphoma with IRF4/DUSP22 rearrangement

Anaplastic large cell lymphomas (ALCL) are mature T-cell neoplasms, approximately half of which harbor rearrangements of the ALK gene that confer a good prognosis. Recent studies have demonstrated that a significant proportion of ALK-negative ALCLs demonstrate rearrangements of the IRF4/DUSP22 locus that also are typically associated with a favorable prognosis. ALCL with primary involvement of the central nervous system (CNS) is extremely rare. We report what may be the first case of ALK-negative ALCL with IRF4/DUSP22 rearrangement involving the brain in a 55-year-old man. Magnetic resonance imaging demonstrated signal abnormalities in the periventricular region, corpus callosum and cingulate gyrus. Biopsy revealed a diffuse parenchymal and angiocentric infiltrate of CD30-positive cells that showed IRF4/DUSP22 rearrangement by fluorescence in situ hybridization. We also review the clinical and pathologic features of primary CNS ALK-negative ALCLs in the literature and highlight the need for awareness of this entity to optimize appropriate management.

ALK-Negative Anaplastic Large Cell Lymphoma: Current Concepts and Molecular Pathogenesis of a Heterogeneous Group of Large T-Cell Lymphomas

Simple Summary

ALK- anaplastic large cell lymphoma (ALK- ALCL) is a rare subtype of CD30+ large T-cell lymphoma that typically affects older adults and has a poor prognosis. Recognition of its histopathologic spectrum, subtypes, and of other tumors that can resemble ALK- ALCL is crucial to avoid making a wrong diagnosis that could result in inappropriate treatment for a patient. In recent years, several important studies have identified recurrent molecular alterations that have shed light on the pathogenesis of this lymphoma. However, on the other hand, putting all this vast information together into a concise form has become challenging. In this review, we present not only a more detailed view of the histopathologic findings of ALK- ALCL but also, we attempt to provide a more simplified perspective of the relevant genetic and molecular alterations of this type of lymphoma, that in our opinion, is not available to date.

Abstract

Anaplastic large cell lymphoma (ALCL) is a subtype of CD30+ large T-cell lymphoma (TCL) that comprises ~2% of all adult non-Hodgkin lymphomas. Based on the presence/absence of the rearrangement and expression of anaplastic lymphoma kinase (ALK), ALCL is divided into ALK+ and ALK-, and both differ clinically and prognostically. This review focuses on the historical points, clinical features, histopathology, differential diagnosis, and relevant cytogenetic and molecular alterations of ALK- ALCL and its subtypes: systemic, primary cutaneous (pc-ALCL), and breast implant-associated (BIA-ALCL). Recent studies have identified recurrent genetic alterations in this TCL. In systemic ALK- ALCL, rearrangements in DUSP22 and TP63 are detected in 30% and 8% of cases, respectively, while the remaining cases are negative for these rearrangements. A similar distribution of these rearrangements is seen in pc-ALCL, whereas none have been detected in BIA-ALCL. Additionally, systemic ALK- ALCL—apart from DUSP22-rearranged cases—harbors JAK1 and/or STAT3 mutations that result in the activation of the JAK/STAT signaling pathway. The JAK1/3 and STAT3 mutations have also been identified in BIA-ALCL but not in pc-ALCL. Although the pathogenesis of these alterations is not fully understood, most of them have prognostic value and open the door to the use of potential targeted therapies for this subtype of TCL.

Update on Pediatric and Young Adult Mature Lymphomas

After acute leukemia and brain and central nervous system tumors, mature lymphomas represent the third most common cancer in pediatric patients. Non-Hodgkin lymphoma accounts for approximately 60% of lymphoma diagnoses in children, with the remainder representing Hodgkin lymphoma. Among non-Hodgkin lymphomas in pediatric patients, aggressive lymphomas, such as Burkitt lymphoma, diffuse large B-cell lymphoma, and anaplastic large cell lymphoma, predominate. This article summarizes the epidemiologic, histopathologic, and molecular features of selected mature systemic B-cell and T-cell lymphomas encountered in this age group.

How I Diagnose Anaplastic Large Cell Lymphoma

OBJECTIVES

This review describes our approach to the diagnosis of all 4 anaplastic large cell lymphoma (ALCL) entities.

METHODS

ALCLs are a group of CD30-positive mature T-cell lymphomas with similar morphologic and phenotypic characteristics but variable clinical and genetic features. They include systemic ALK-positive ALCL, systemic ALK-negative ALCL, primary cutaneous ALCL, and the recently described provisional entity breast implant-associated ALCL.

RESULTS

In cases with classic features, the diagnosis of ALCL is often straightforward. However, variant histology, the importance of clinical history, and multiple antigenic aberrancies all present challenges to accurate diagnosis and subclassification.

CONCLUSIONS

A systematic approach to the diagnosis of ALCL and awareness of potential mimics are critical to avoid misdiagnosis. It is also crucial to correctly identify localized forms of ALCL to avoid classification as systemic ALCL and subsequent overtreatment.

Hematolymphoid Neoplasms Rarely Mimic Undifferentiated Pleomorphic Sarcoma of Soft Tissue

CONTEXT.—

Undifferentiated pleomorphic sarcoma (UPS) of soft tissue is defined as a sarcoma with no recognizable line of differentiation. During the past few decades, advances in ancillary studies and review of prior UPS diagnoses have narrowed the category of UPS by excluding more-specific malignancies. However, few of those studies have specifically targeted pleomorphic hematolymphoid neoplasms.

OBJECTIVE.—

To determine what fraction of UPS cases are misclassified pleomorphic hematolymphoid neoplasms, such as anaplastic large cell lymphoma, diffuse large B-cell lymphoma, histiocytic sarcoma (HS), myeloid sarcoma, and follicular dendritic cell sarcoma.

DESIGN.—

Sixty-one UPS cases were screened by tissue microarray and an immunostain panel with subsequent analysis on whole block sections for suspicious cases.

RESULTS.—

Five of 61 tumors (8%) were suggestive of HS based on the screening panel and were further evaluated with additional immunostains (PU.1, CD45, CD163) using whole sections. The 5 candidate HS cases were only focally positive for at most one stain with most staining in smaller, less-pleomorphic cells. Ultimately, no UPS met criteria for anaplastic large cell lymphoma, diffuse large B-cell lymphoma, myeloid sarcoma, follicular dendritic cell sarcoma, or HS.

CONCLUSIONS.—

Our results suggest that a UPS of somatic soft tissue is unlikely to represent a misclassified hematopoietic malignancy. Exclusion of HS is most challenging, but immunostaining for PU.1, a nuclear transcription factor, may be easier to interpret in this context.

Anaplastic lymphoma kinase-positive anaplastic large cell lymphoma presenting as diffuse pulmonary infiltrates

Anaplastic large cell lymphoma has a characteristic sinusoidal growth pattern that presents as pulmonary lymphangitic involvement causing respiratory distress. Recognition and prompt treatment of this entity can result in dramatic response to therapy.

Clinical, Histologic, and Molecular Characteristics of Anaplastic Lymphoma Kinase-positive Primary Cutaneous Anaplastic Large Cell Lymphoma

Unlike systemic anaplastic large cell lymphoma, the vast majority of primary cutaneous anaplastic large cell lymphomas (C-ALCL) do not carry translocations involving the ALK gene and do not express ALK. Expression of ALK protein therefore strongly suggests secondary cutaneous involvement of a systemic anaplastic large cell lymphoma. Recent studies described a small subgroup of ALK-positive C-ALCL, but information on frequency, prognosis, and translocation partners is virtually lacking. A total of 6/309 (2%) C-ALCL patients included in the Dutch registry for cutaneous lymphomas between 1993 and 2019 showed immunohistochemical ALK expression. Clinical and histopathologic characteristics, immunophenotype and disease course were evaluated. Underlying ALK translocations were analyzed with anchored multiplex polymerase chain reaction-based targeted next-generation sequencing. Median age at diagnosis was 39 years (range: 16 to 53 y). All patients presented with a solitary lesion. Treatment with radiotherapy (n=5) or anthracycline-based chemotherapy (n=1) resulted in complete responses in all 6 patients. Three patients developed a relapse, of whom 2 extracutaneous. After a median follow-up of 41 months, 5 patients were alive without disease and 1 patient died of lymphoma. Immunohistochemically, 3 cases (50%) showed combined nuclear and cytoplasmic ALK expression with underlying NPM1-ALK fusions, while 3 cases (50%) showed solely cytoplasmic ALK expression with variant ALK fusion partners (TRAF1, ATIC, TPM3). ALK-positive C-ALCL is extremely uncommon, has a comparable favorable prognosis to ALK-negative C-ALCL, and should be treated in the same way with radiotherapy as first-line treatment.

ALK-Positive Histiocytosis with Peripheral Blood Histiocytes: A Case Report

Histiocytoses are a diverse group of rare, clinically heterogeneous disorders characterised by tissue infiltration of histiocytes, which may result in organ dysfunction and failure. Over 100 different subtypes of histiocytoses have been recognised, including rare cases of ALK-positive histiocytosis. We report a case of histiocytosis in a neonate who presented with refractory thrombocytopenia, anaemia, and intermittent neutropenia. Histiocytes were present in both peripheral blood smears and bone marrow; ALK positivity was demonstrated by immunohistochemistry. Given the scarce reports of this condition, the variable organ involvement, and the different approaches to management in the cases described, we seek to expand the literature by providing a report of our patient whose condition improved without chemotherapy. The presence of histiocytes in peripheral blood smears of patients with this condition has not previously been reported, and it underscores the importance of routine careful evaluation of blood smears.

Intensive Induction Therapy Compared With CHOP for Hepatosplenic T-cell Lymphoma

INTRODUCTION

Hepatosplenic T-cell lymphoma (HSTCL) is a rare peripheral T-cell lymphoma that disproportionately affects individuals with a clinical history of immunosuppression. It carries a poor prognosis, and, owing to its rarity, there is no single or well-established treatment.

PATIENTS AND METHODS

We conducted the largest-to-date individual-level meta-analysis based on literature searches to determine the best induction therapy for HSTCL. We compared response rates and survival among patients who received "non-CHOP-based" induction with regimens containing cytarabine, etoposide, and/or platinum-based treatment to those receiving treatment with CHOP (cyclophosphamide, doxorubicin, vincristine, and prednisone) or CHOP-like therapy. We also review additional regimens including alemtuzumab and pentostatin, and assessed the role of consolidation with hematopoietic stem-cell transplantation (HSCT).

RESULTS

We identified 166 patients with HSTCL, 118 of whom had sufficient information on induction treatment and survival. Eighty-four patients received non-CHOP-based (N = 34) or CHOP/CHOP-like (N = 50) induction treatment. Non-CHOP-based induction was associated with a complete/partial response rate of 82% compared with 52% (P = .006) with CHOP/CHOP-like and increased median overall survival (P = .00014). Our data showed that maximum survival among patients with HSTCL was achieved with non-CHOP-based induction followed by consolidation with HSCT.

CONCLUSIONS

Non-CHOP-based induction appears superior to CHOP/CHOP-like induction in both achieving complete/partial response and durable survival. Induction therapy of HSTCL should be intensified with non-CHOP-based regimens and followed by consolidation with HSCT in eligible patients.

A Systematic Approach to the Cutaneous Lymphoid Infiltrates: A Clinical, Morphologic, and Immunophenotypic Evaluation

CONTEXT.—

The evaluation of cutaneous lymphoid infiltrates, both neoplastic and inflammatory, occurs very frequently in routine dermatopathologic examination and consultation practices. The "tough" cutaneous lymphoid infiltrate is feared by many pathologists; skin biopsies are relatively small, whereas diagnostic possibilities are relatively broad. It is true that cutaneous lymphomas can be difficult to diagnose and that in many circumstances multiple biopsies are required to establish a correct diagnostic interpretation. As a reminder, one should understand that low-grade cutaneous lymphomas are indolent disorders that usually linger for decades and that therapy does not result in disease cure. It is also important to remember that in most circumstances, those patients will die from another process that is completely unrelated to a diagnosis of skin lymphoma (even in the absence of specific therapy).

OBJECTIVE.—

To use a clinicopathologic, immunophenotypic, and molecular approach in the evaluation of common lymphocytic infiltrates.

DATA SOURCES.—

An in-depth analysis of updated literature in the field of cutaneous lymphomas was done, with particular emphasis on updated terminology from the most recent World Health Organization classification of skin and hematologic tumors.

CONCLUSIONS.—

A diagnosis of cutaneous lymphoid infiltrates can be adequately approached using a systematic scheme following the proposed ABCDE system. Overall, cutaneous T- and B-cell lymphomas are rare and "reactive" infiltrates are more common. Evaluation of lymphoid proliferations should start with a good sense of knowledge of the clinical presentation of the lesions, the clinical differential considerations, and a conscientious and appropriate use of immunohistochemistry and molecular tools.

Pathology and genetics of anaplastic large cell lymphoma

Anaplastic large cell lymphomas are a rare subtype of peripheral/mature T-cell lymphomas which are clinically, pathologically and genetically heterogeneous. Both ALK-positive (ALK+) and ALK-negative (ALK-) ALCL are composed of large lymphoid cells with abundant cytoplasm and pleomorphic features with horseshoe-shaped and reniform nuclei. ALK+ ALCL were considered as a definite entity in the 2008 World Health Organization classification of hematopoietic and lymphoid tissues. ALK-ALCL was included as a provisional entity in the WHO 2008 edition and in the most recent 2017 edition, it is now considered a distinct entity that includes cytogenetic subsets that appear to have prognostic implications (e.g. 6p25 rearrangements at IRF4/DUSP22 locus). ALK+ ALCLs are distinct in epidemiology and pathogenetic origin and should be distinguished from ALK-ALCL, cutaneous ALCL and breast implant associated ALCL which have distinct clinical course and pathogenetic features. Breast implant-associated ALCL is now recognized as a new provisional entity distinct from other ALK-ALCL; notably that it is a noninvasive disease associated with excellent outcome. In this article, we will provide an overview of the salient themes relevant to the pathology and genetic mechanisms in ALCL.

Approach to nodal-based T-cell lymphomas

Peripheral T-cell lymphomas (PTCLs) represent a heterogeneous group of uncommon malignancies derived from mature T cells and usually characterised by an aggressive clinical course. Their clinical presentation, localisation and pattern of dissemination are highly variable, but the majority of cases present as nodal diseases. The recently revised classification of lymphomas has incorporated many new molecular genetic data derived from gene expression profiling and next generation sequencing studies, which refine the definition and diagnostic criteria of several entities. Nevertheless, the distinction of PTCL from various reactive conditions, and the diagnosis of PTCL subtypes remains notably challenging. Here, an updated summary of the clinicopathological and molecular features of the most common nodal-based PTCLs (angioimmunoblastic T-cell lymphoma and other nodal lymphomas derived from follicular T helper cells, anaplastic large cell lymphomas and peripheral T-cell lymphoma, not otherwise specified) is presented. Practical recommendations in the diagnostic approach to nodal T-cell lymphoproliferations are presented, including indications for the appropriate use and interpretation of ancillary studies. Finally, we discuss commonly encountered diagnostic problems, including pitfalls and mimics in the differential diagnosis with various reactive conditions, and the criteria that allow proper identification of distinct PTCL entities.

Prognostic Factors and Treatment Outcome of Pediatric Anaplastic Large Cell Lymphoma Treated at the Children Cancer Hospital Egypt

INTRODUCTION

The aim of the current study is to report the epidemiologic data, response rate, treatment outcome, and overall survival of anaplastic large cell lymphoma (ALCL) patients during the 8-year period.

PATIENTS AND METHODS

A retrospective study included all patients with newly diagnosed ALCL from July 2007 till December 2015.

RESULTS

A total of 48 patients were enrolled. The majority (66.7%) were male individuals. Twenty-one patients (43.7%) were low stage I or II, whereas 27 (56.2%) had advanced stage III or IV. Two patients (4.2%) died during induction chemotherapy. Disease status at last follow-up showed 35 patients (72.9%) in complete remission, 5 (10.5%) relapse, and 5 disease progression. The median time to relapse was 17.2 months. Four patients (8.4%) were salvaged by high-dose chemotherapy ifosphamide, carboplatine, etoposide followed by autologous hematopoietic stem cell transplantation, whereas 5 (10.5%) died out of disease progression. The 5-year overall survival and event-free survival were 81.2% and 68.6%, respectively. Median FU period was 58.7 month. Multivariate analysis included age, sex, stage, and response to chemotherapy and showed no statistical significance.

CONCLUSION

Treatment of ALCL according to the Children's Oncology Group ANHL 0131 protocol is well tolerated. The relapsing patient could be salvaged by high-dose chemotherapy and autologous hematopoietic stem cell transplantation.

Abdominal Pain and Intermittent Fevers in a 16-Year-Old Girl

A 16-year-old girl presented to the emergency department with intermittent fevers and worsening abdominal pain of 5 weeks duration. She had a history of travel to a less developed country and exposure to possible infectious diseases. Abdominal imaging and blood tests revealed diffuse mesenteric lymphadenopathy, elevated transaminases, and elevation of inflammatory markers. Gastroesophageal and colon endoscopies revealed gastric ulcers, and the patient was discharged with a presumptive diagnosis of systemic juvenile idiopathic arthritis given the lymphadenopathy seen on imaging, serositis, sacroiliac joint stiffness noted on physical examination, and pain relief with celecoxib. She presented again 4 days later with worsening abdominal tenderness, elevated transaminases, and new-onset abdominal distention. Tissue biopsy yielded the diagnosis and directed appropriate treatment.

Update on the classification of T-cell lymphomas, Hodgkin lymphomas, and histiocytic/dendritic cell neoplasms

Introduction: The classification of lymphomas is based on the postulated normal counterparts of lymphoid neoplasms and currently constitutes over 100 definite or provisional entities. As this number of entities implies, lymphomas show marked pathological, genetic, and clinical heterogeneity. Recent molecular findings have significantly advanced our understanding of lymphomas. Areas covered: The World Health Organization (WHO) classification of lymphoid neoplasms was updated in 2017. The present review summarizes the new findings that have been gained in the areas of mature T-cell neoplasms, Hodgkin lymphomas, and histiocytic/dendritic cell neoplasms since the publication of the 2017 WHO classification. Expert opinion: Although formal revisions to the WHO classification are published only periodically, our understanding of the pathologic, genetic, and clinical features of lymphoid neoplasms is constantly evolving, particularly in the age of -omics technologies and targeted therapeutics. Even in the relatively short time since the publication of the 2017 WHO classification, many significant findings have been identified in the entities covered in this review.

Clinical Features and Treatment Outcomes of Children With Anaplastic Large Cell Lymphoma in Pakistan: A Multicenter Study

BACKGROUND

Different approaches have been adopted in the treatment of anaplastic large cell lymphoma (ALCL); there is a lack of consensus with regard to standard treatment. Because of paucity of data from low and middle-income countries, we reviewed the clinical features and treatment outcomes of children with ALCL.

METHODS

All ALCL patients under 16 years of age diagnosed from 2005 to 2015 at Aga Khan University Hospital and The Indus Hospital were identified. Clinical features and treatment outcomes were analyzed.

RESULTS

Thirty-two (n=32) patients met the inclusion criteria. Cervical Lymphadenopathy was the most common presentation (34.3%, n=11). Advanced disease was seen in 68.7% (n=22) (stages III and IV). Fourteen (42.4%) were treated on ALCL-99, 30.3% (n=10) on multicenter protocol-842 regimen, 9% (n=3) on adriamycin-prednisolone-oncovin (doxorubicin, prednisone, vincristine) regimen, and 16% (n=5) were treatment abandonments. Five-year overall survival was 70.6% (95% confidence interval: 47.8%-84.9%), and 5-year event-free survival (EFS) considering treatment abandonment and death as an event was 52.3 % (95% confidence interval: 23.5%-74.8%).

CONCLUSIONS

Significant therapy-related mortality (27.7%) was observed. Treatment abandonment and therapy-related toxicity were the major barriers for better outcomes. However, less intensive outpatient regimens, such as adriamycin-prednisolone-oncovin regimen, may decrease the number of hospitalizations, hence reducing treatment abandonment in the low and middle-income country.

From bench to bedside: the past, present and future of therapy for systemic paediatric ALCL, ALK

Anaplastic large cell lymphoma (ALCL) is a T cell Non-Hodgkin Lymphoma that mainly presents in paediatric and young adult patients. The majority of cases express a chimeric fusion protein resulting in hyperactivation of anaplastic lymphoma kinase (ALK) as the consequence of a chromosomal translocation. Rarer cases lack expression of ALK fusion proteins and are categorised as ALCL, ALK-. An adapted regimen of an historic chemotherapy backbone is still used to this day, yielding overall survival (OS) of over 90% but with event-free survival (EFS) at an unacceptable 70%, improving little over the past 30 years. It is clear that continued adaption of current therapies will probably not improve these statistics and, for progress to be made, integration of biology with the design and implementation of future clinical trials is required. Indeed, advances in our understanding of the biology of ALCL are outstripping our ability to clinically translate them; laboratory-based research has highlighted a plethora of potential therapeutic targets but, with high survival rates combined with a scarcity of funding and patients to implement paediatric trials of novel agents, progress is slow. However, advances must be made to reduce the side-effects of intensive chemotherapy regimens whilst maintaining, if not improving, OS and EFS.

Pearls and pitfalls in the diagnostic workup of small lymph node biopsies

All pathology subspecialties are more frequently receiving small needle core biopsies for the diagnosis of new lesions. While this results in potential diagnostic pitfalls, the tools available for hematopathology, including extensive panels of immunostains, PRC-based clonality assessment, and flow cytometry often allow accurate diagnoses even with very small specimens. This review presents a brief approach to such biopsies, using morphologic cues as well as ancillary studies, which provides an experience-based framework for approaching these cases and coming to a clear diagnosis while avoiding diagnostic errors. The approach is divided into three parts based on H & E cell morphology.

Molecular profiling reveals immunogenic cues in anaplastic large cell lymphomas with DUSP22 rearrangements

Anaplastic large cell lymphomas (ALCLs) are CD30-positive T-cell non-Hodgkin lymphomas broadly segregated into ALK-positive and ALK-negative types. Although ALK-positive ALCLs consistently bear rearrangements of the ALK tyrosine kinase gene, ALK-negative ALCLs are clinically and genetically heterogeneous. About 30% of ALK-negative ALCLs have rearrangements of DUSP22 and have excellent long-term outcomes with standard therapy. To better understand this group of tumors, we evaluated their molecular signature using gene expression profiling. DUSP22-rearranged ALCLs belonged to a distinct subset of ALCLs that lacked expression of genes associated with JAK-STAT3 signaling, a pathway contributing to growth in the majority of ALCLs. Reverse-phase protein array and immunohistochemical studies confirmed the lack of activated STAT3 in DUSP22-rearranged ALCLs. DUSP22-rearranged ALCLs also overexpressed immunogenic cancer-testis antigen (CTA) genes and showed marked DNA hypomethylation by reduced representation bisulfate sequencing and DNA methylation arrays. Pharmacologic DNA demethylation in ALCL cells recapitulated the overexpression of CTAs and other DUSP22 signature genes. In addition, DUSP22-rearranged ALCLs minimally expressed PD-L1 compared with other ALCLs, but showed high expression of the costimulatory gene CD58 and HLA class II. Taken together, these findings indicate that DUSP22 rearrangements define a molecularly distinct subgroup of ALCLs, and that immunogenic cues related to antigenicity, costimulatory molecule expression, and inactivity of the PD-1/PD-L1 immune checkpoint likely contribute to their favorable prognosis. More aggressive ALCLs might be pharmacologically reprogrammed to a DUSP22-like immunogenic molecular signature through the use of demethylating agents and/or immune checkpoint inhibitors.

The Pathological Spectrum of Systemic Anaplastic Large Cell Lymphoma (ALCL)

Anaplastic large cell lymphoma (ALCL) represents a group of malignant T-cell lymphoproliferations that share morphological and immunophenotypical features, namely strong CD30 expression and variable loss of T-cell markers, but differ in clinical presentation and prognosis. The recognition of anaplastic lymphoma kinase (ALK) fusion proteins as a result of chromosomal translocations or inversions was the starting point for the distinction of different subgroups of ALCL. According to their distinct clinical settings and molecular findings, the 2016 revised World Health Organization (WHO) classification recognizes four different entities: systemic ALK-positive ALCL (ALK+ ALCL), systemic ALK-negative ALCL (ALK− ALCL), primary cutaneous ALCL (pC-ALCL), and breast implant-associated ALCL (BI-ALCL), the latter included as a provisional entity. ALK is rearranged in approximately 80% of systemic ALCL cases with one of its partner genes, most commonly NPM1, and is associated with favorable prognosis, whereas systemic ALK− ALCL shows heterogeneous clinical, phenotypical, and genetic features, underlining the different oncogenesis between these two entities. Recognition of the pathological spectrum of ALCL is crucial to understand its pathogenesis and its boundaries with other entities. In this review, we will focus on the morphological, immunophenotypical, and molecular features of systemic ALK+ and ALK− ALCL. In addition, BI-ALCL will be discussed.

Primary Bone Anaplastic Large Cell Lymphoma Masquerading as Ewing Sarcoma: Diagnosis by Anchored Multiplex PCR

A 3-year-old boy presented with pathologic fracture of the left proximal femur. Magnetic resonance imaging revealed an aggressive expansile bony mass associated with cortical destruction and surrounding myositis. Computed tomography-guided biopsy revealed a monomorphic small round blue cell tumor by histology. CD99 immunoreactivity and low-level EWSR1 gene translocation by break-apart fluorescent in situ hybridization initially favored a diagnosis of Ewing sarcoma and chemotherapy commenced. Subsequent molecular evaluation by an anchored multiplex polymerase chain reaction-based assay (Archer FusionPlex Sarcoma Panel) revealed a nucleophosmin-anaplastic lymphoma kinase (NPM-ALK) gene fusion. The diagnosis was then amended to primary bone ALK-positive anaplastic large cell lymphoma and the chemotherapy regimen was modified accordingly. This report illustrates the value of this molecular assay in establishing the correct diagnosis of a very rare malignancy masquerading as another tumor type.