Primary renal leukaemia in a young adult male as an extramedullary presentation of T cell acute lymphoblastic leukaemia.

Primary renal involvement by T lymphoblasts is rare among adults with T acute lymphoblastic leukaemia. We report a 28-year-old man presenting with acute renal failure due to infiltration by T lymphoblasts and his response to paediatric-inspired modified BFM-90 protocol. The patient achieved an initial complete remission (CR) but developed central nervous system relapse. He achieved CR2 with cranial irradiation and intrathecal chemotherapy. He underwent a haploidentical transplant in CR2 and remains in remission post-transplant day 330. An early kidney biopsy helped confirm the diagnosis. Such presentations remain responsive to modified BFM-90. An early allotransplant in CR2 remains the standard of care.

TFG::ALK fusion in ALK positive large B-cell lymphoma: a case report and review of literature.

Anaplastic lymphoma kinase (ALK) positive large B-cell lymphoma (ALK+ LBCL) is an aggressive and rare subtype of B-cell lymphoma. Patients typically present with advanced clinical stage disease and do not respond to conventional chemotherapy; the median overall survival is 1.8 years. The genetic landscape of this entity remains poorly understood. Here we report a unique case of ALK+ LBCL harbouring a rare TFG::ALK fusion. Targeted next-generation sequencing showed no significant single nucleotide variants, insertions/deletions, or other structural variants beyond the TFG::ALK fusion; deep deletions of FOXO1, PRKCA, and the MYB locus were also detected. Our case report draws attention to this rare disease, highlights a need for larger genetic profiling studies, and focuses on the pathogenesis and potential therapeutic targets of this aggressive disease. To our knowledge, this is the first report of a TFG::ALK fusion in ALK+ LBCL.

Profiling endogenous, environmental, and infectious disease mutational signatures in blastic plasmacytoid dendritic cell neoplasms.

BACKGROUND: Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare hematopoietic disease derived from plasmacytoid dendritic lineage cells. The disease typically shows skin as well as frequent bone marrow and peripheral blood involvement. However, the pathogenesis of this disease is still not well understood. While somatic point mutations and genetic rearrangements have been described in BPDCN, the types and origins of these mutations and relationships to other cancer types is not well understood. MATERIALS AND METHODS: To probe the origins of BPDCN, we analyzed the exome sequence data of 9 tumor-normal pair cases of BPDCN. We utilized SignatureAnalyzer, SigProfiler and a custom microbial analysis pipeline to understand the relevance of endogenous and environmental mutagenic processes. RESULTS: Our results identified a significant tobacco exposure and aging genetic signature as well as signatures related to nucleotide excision repair deficiency, ultra violet (UV) exposure, and endogenous deamination in BPDCN. We also assessed the samples for microbial infectious disease organisms but did not find a link to a microbial etiology. CONCLUSION: The identification of a tobacco exposure and aging genetic signature in patients with BPDCN suggests that environmental and endogenous genetic changes may be central to the oncogenesis of BPDCN.

Smoking status in acute myeloid leukemia is associated with worse overall survival and independent of prior nonhematopoietic malignancies, cytogenetic abnormalities, and WHO category.

Acute myeloid leukemia (AML) is an aggressive hematopoietic malignancy with several patient- and disease-associated variables known to impact prognosis. Tobacco smoking is an environmental factor associated with a greater incidence of AML, but there have been limited studies that evaluated smoking toward overall survival. We retrospectively searched for AML cases and collected clinical and diagnostic data for each case. We also used an independent next-generation sequencing (NGS) data set to assess for a distinct mutational signature associated with smoking. When stratified by smoking status, there was a greater number of males, patients aged ≥60 years, and patients with ≥2 comorbidities within the smoking category (P < .05). Survival analysis demonstrated decreased survival probability in the smokers, male smokers, smokers with 1 other comorbidity, and smokers without a prior history of nonhematopoietic malignancy (P < .05) as compared to nonsmokers. Smoking was associated with a decrease in survival within the World Health Organization categories of AML, not otherwise specified (AML NOS; P = .035) and AML with recurrent genetic abnormalities (AML RGA; P = .002). Multivariate analysis showed that patients who were smokers had a greater hazard ratio than nonsmokers after adjusting for the other covariates. Our findings demonstrated that smoking was independently associated with decreased overall survival after adjusting for other potentially confounding factors. In addition, our results suggest that a mutational signature can be recognized using NGS data in a subset of AML patients who smoke.

Copy Number Loss at Chromosome 14q11.2 Correlates With the Proportion of T Cells in Biopsies and Helps Identify T-Cell Neoplasms.

CONTEXT.­: Evidence of T-cell clonality is often critical in supporting the diagnosis of a T-cell lymphoma. OBJECTIVES.­: To retrospectively explore the significance of copy number losses at the 14q11.2 T-cell receptor α locus in relation to the presence of a T-cell neoplasm and proportion of T cells by targeted next-generation sequencing. DESIGN.­: Targeted next-generation sequencing data from 139 tissue biopsies, including T-cell lymphomas, B-cell lymphomas, classic Hodgkin lymphomas, nonhematopoietic malignancies, and normal samples, were reviewed for copy number losses involving the T-cell receptor α gene segments at chr14q11.2. RESULTS.­: We found that biallelic or homozygous deletion of 14q11.2 was found in most (28 of 33, 84.8%) T-cell lymphomas. The magnitude of 14q11.2 loss showed a statistically significant correlation with the proportion of T cells in lymphoma tissue samples. Copy number losses could also be detected in other lymphomas with high numbers of T cells (8 of 32, 25% of B-cell lymphomas, 4 of 4 classical Hodgkin lymphomas), though biallelic/homozygous deletion of 14q11.2 was not significantly observed outside of T-cell lymphomas. Most nonhematopoietic neoplasms and normal tissues (59 of 64, 92.2%) showed no significant copy number losses involving the T-cell receptor α locus at chr14q11.2. CONCLUSIONS.­: Analysis of copy number losses at the T-cell receptor α locus chr14q11.2 with targeted next-generation sequencing can potentially be used to estimate the proportion of T cells and detect T-cell neoplasms.

An Analysis of the Pathologic Features of Blastic Plasmacytoid Dendritic Cell Neoplasm Based on a Comprehensive Literature Database of Cases.

CONTEXT.­: Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare hematologic malignancy with poor outcome. BPDCN diagnostically overlaps with entities such as acute myeloid leukemia, histiocytic/dendritic cell neoplasms, and natural killer/T-cell lymphomas. Unfortunately, large, patient-centered studies that comprehensively analyze clinical, pathologic, and other diagnostic features are lacking. As such, there is an incomplete understanding of this disease. OBJECTIVE.­: To better characterize BPDCN, a multicenter working group consisting of hematopathologists and dermatopathologists gathered in person and remotely to review the current understanding of BPDCN, discuss specific issues regarding the diagnosis and differential diagnosis, and perform a retrospective analysis of the literature. DATA SOURCES.­: The working group curated a database of published BPDCN patient cases (BPDCN Network literature database), and following careful discussion and review, 361 articles were identified, comprising a total of 1513 individually annotated patients. CONCLUSIONS.­: By conducting an in-depth analysis, not only did we confirm known findings such as frequent skin involvement (84% of patients; 861 of 1028) and a male predominance among older patients (>60 years old; male to female ratio of 3.5:1; 617:177), but we also identified a number of underrecognized features, such as significant central nervous system involvement (38% of cases; 24 of 64), and a more equal male to female prevalence among patients younger than 40 years (male to female ratio of 1.25:1; 167:134). Furthermore, we were able to accurately summarize the immunophenotypic, cytogenetic, and molecular features of this disease. BPDCN is a complex disease with distinct morphologic, immunophenotypic, and molecular findings. Continual updates of the literature database generated here and further analysis can allow for prospective refinement of our understanding of this orphan disease.

Cytomorphologic features of pediatric-type follicular lymphoma on fine needle aspiration biopsy: case series and a review of the literature.

INTRODUCTION: Pediatric-type follicular lymphoma (PTFL) is a rare and recently recognized subtype of nodal follicular B-cell lymphoma. While significant recent progress has been made in understanding the morphologic, immunophenotypic, and molecular findings, there are only rare case reports describing the cytomorphologic features of PTFL. MATERIALS AND METHODS: Four cases of PTFL initially evaluated on fine needle aspiration (FNA) biopsy were retrieved from our institutions' databases. The cytologic and subsequent surgical excision specimens were compared in terms of cytology, histology, immunophenotype, and molecular findings. RESULTS: A constellation of cytologic features for PTFL are able to distinguish it from other cytomorphologic entities in the differential including: 1) the presence of large blastoid cells with fine chromatin and irregular nuclear membranes, 2) small/intermediate-sized lymphocytes with subtle nuclear membrane irregularities, 3) near complete absence of cytoplasmic vacuoles in lymphoid cells, 4) tingible body macrophages, 5) mitotic figures, 6) absence of a diffuse large cell component, 7) and no significant plasma cell population. CONCLUSIONS: We present four cases of PTFL initially evaluated on FNA biopsy and define the cytomorphologic features of PTFL. FNA biopsy is presented as a practical tool for initial evaluation of this rare entity as part of a multimodal diagnostic approach, for which increased awareness among cytopathologists can ensure the appropriate triage of specimen studies necessary for the diagnosis. Additionally, we comprehensively review the current literature on PTFL and discuss the differential diagnosis on cytology, including potential pitfalls.

Indolent T-lymphoblastic proliferation: A systematic review of the literature analyzing the epidemiologic, clinical, and pathologic features of 45 cases.

An indolent T-lymphoblastic proliferation (iT-LBP) is a rare benign disorder characterized by an abnormal expansion of immature T-cells, which morphologically can mimic malignancy. Since the first case was described in 1999, dozens more have been reported in the literature. However, the epidemiologic, clinical, pathologic, and biologic features of this disease have not been well described. Here, we retrospectively reviewed all known cases reported in the literature to better understand this entity. A PubMed search up to January 2022 highlighted 25 papers describing cases/case series of iT-LBP, one of which was a case presentation in a slide workshop. Except for 9 of the cases in one of the papers, where it was evident that the number of CD3+/TdT+ cells were too few to conform with a diagnosis of iT-LBP, all papers and all the cases reported were included in the study amounting to a total of 45 cases. Clinicopathologic characteristics were analyzed using descriptive statistics and frequencies. Our analysis highlighted the previously known association with Castleman disease and Castleman-like features and underlined its association with dendritic cell proliferations in general, as well as uncovering high frequency of concurrence with hepatocellular carcinoma and autoimmune diseases, most notably myasthenia gravis, paraneoplastic pemphigus and paraneoplastic autoimmune multiorgan syndrome. Furthermore, the co-expression of CD4 and CD8 and high prevalence of extranodal disease and recurrences were other less well described features that were revealed.

Case Report: Castleman Disease With an Associated Stromal Spindle Cell Proliferation, PDGFRB Mutation and p53 Expression: Clonal Origins of a Rare Disease.

Castleman disease (CD) is a rare lymphoproliferative disorder with distinct clinical subtypes. However, our understanding of the underlying pathogenesis of particular subtypes of CD remains unclear. While the characteristic morphologic changes within UCD, including occasional cases of overgrowth of spindled stromal and follicular dendritic cells have been described, the nature and origin of these spindle cells remain elusive. Few reports have suggested that underlying stromal cells in UCD are clonally neoplastic and may be of fibroblastic reticular cell (FRC) or follicular dendritic cell (FDC) origins given their close clonal relationship. Although certain histomorphologic features may aid diagnosis, there are no specific biomarkers that can differentiate a reactive process mimicking UCD from true UCD. Hence, we describe an index case with morphology consistent with the hyaline vascular subtype of UCD with concomitant atypical smooth muscle actin (SMA)-positive stromal spindle cell proliferation containing a recurrent PDGFRB N666S mutation and upregulation of p53 expression. Further analysis of 21 additional cases of UCD identified increased p53 expression by digital image analysis and SMA positive stromal cells predominantly within the paracortical and intrafollicular areas further strengthening the hypothesis of the stromal cellular derivation and origins of UCD.

Pathology updates and diagnostic approaches to haemophagocytic lymphohistiocytosis.

Haemophagocytic lymphohistiocytosis (HLH) is a complex, often under-recognised hyperinflammatory immune dysregulation syndrome arising in a diverse range of clinical scenarios and conditions. The accurate and timely diagnosis of HLH is crucial for patient survival, and usually requires a high level of clinical suspicion. The histological corollary to clinical HLH-haemophagocytosis-is neither necessary nor sufficient for the diagnosis of HLH, as it may be seen in a variety of reactive conditions and may be absent in true HLH. Nevertheless, the finding of haemophagocytosis in specific clinical situations should prompt consideration of HLH and further testing to exclude the condition. Although haemophagocytosis is traditionally described in bone marrow, identification of it in other tissues, including lymphoid, splenic, liver or neural tissue, can contribute importantly to the overall recognition of HLH. In this review we discuss the underlying pathophysiology and aetiologies of HLH, and the morphological aspects of haemophagocytosis and its associated histological findings in different tissues, and give a brief overview of diagnostic criteria and clinical evaluation.

Lymphoid blast transformation in an MPN with BCR-JAK2 treated with ruxolitinib: putative mechanisms of resistance.

The basis for acquired resistance to JAK inhibition in patients with JAK2-driven hematologic malignancies is not well understood. We report a patient with a myeloproliferative neoplasm (MPN) with a BCR activator of RhoGEF and GTPase (BCR)-JAK2 fusion with initial hematologic response to ruxolitinib who rapidly developed B-lymphoid blast transformation. We analyzed pre-ruxolitinib and blast transformation samples using genome sequencing, DNA mate-pair sequencing (MPseq), RNA sequencing (RNA-seq), and chromosomal microarray to characterize possible mechanisms of resistance. No resistance mutations in the BCR-JAK2 fusion gene or transcript were identified, and fusion transcript expression levels remained stable. However, at the time of blast transformation, MPseq detected a new IKZF1 copy-number loss, which is predicted to result in loss of normal IKZF1 protein translation. RNA-seq revealed significant upregulation of genes negatively regulated by IKZF1, including IL7R and CRLF2. Disease progression was also characterized by adaptation to an activated B-cell receptor (BCR)-like signaling phenotype, with marked upregulation of genes such as CD79A, CD79B, IGLL1, VPREB1, BLNK, ZAP70, RAG1, and RAG2. In summary, IKZF1 deletion and a switch from cytokine dependence to activated BCR-like signaling phenotype represent putative mechanisms of ruxolitinib resistance in this case, recapitulating preclinical data on resistance to JAK inhibition in CRLF2-rearranged Philadelphia chromosome-like acute lymphoblastic leukemia.

Point Mutation Specific Antibodies in B-Cell and T-Cell Lymphomas and Leukemias: Targeting IDH2, KRAS, BRAF and Other Biomarkers RHOA, IRF8, MYD88, ID3, NRAS, SF3B1 and EZH2.

B-cell and T-cell lymphomas and leukemias often have distinct genetic mutations that are diagnostically defining or prognostically significant. A subset of these mutations consists of specific point mutations, which can be evaluated using genetic sequencing approaches or point mutation specific antibodies. Here, we describe genes harboring point mutations relevant to B-cell and T-cell malignancies and discuss the current availability of these targeted point mutation specific antibodies. We also evaluate the possibility of generating novel antibodies against known point mutations by computationally assessing for chemical and structural features as well as epitope antigenicity of these targets. Our results not only summarize several genetic mutations and identify existing point mutation specific antibodies relevant to hematologic malignancies, but also reveal potential underdeveloped targets which merit further study.

A Review of Genetic Abnormalities in Unicentric and Multicentric Castleman Disease.

Castleman disease (CD) is a rare lymphoproliferative disorder known to represent at least four distinct clinicopathologic subtypes. Large advancements in our clinical and histopathologic description of these diverse diseases have been made, resulting in subtyping based on number of enlarged lymph nodes (unicentric versus multicentric), according to viral infection by human herpes virus 8 (HHV-8) and human immunodeficiency virus (HIV), and with relation to clonal plasma cells (POEMS). In recent years, significant molecular and genetic abnormalities associated with CD have been described. However, we continue to lack a foundational understanding of the biological mechanisms driving this disease process. Here, we review all cases of CD with molecular abnormalities described in the literature to date, and correlate cytogenetic, molecular, and genetic abnormalities with disease subtypes and phenotypes. Our review notes complex karyotypes in subsets of cases, specific mutations in PDGFRB N666S in 10% of unicentric CD (UCD) and NCOA4 L261F in 23% of idiopathic multicentric CD (iMCD) cases. Genes affecting chromatin organization and abnormalities in methylation are seen more commonly in iMCD while abnormalities within the mitogen-activated protein kinase (MAPK) and interleukin signaling pathways are more frequent in UCD. Interestingly, there is a paucity of genetic studies evaluating HHV-8 positive multicentric CD (HHV-8+ MCD) and POEMS-associated CD. Our comprehensive review of genetic and molecular abnormalities in CD identifies subtype-specific and novel pathways which may allow for more targeted treatment options and unique biologic therapies.

Mutations in JAK/STAT and NOTCH1 Genes Are Enriched in Post-Transplant Lymphoproliferative Disorders.

Post-transplant lymphoproliferative disorders (PTLD) are diseases occurring in immunocompromised patients after hematopoietic stem cell transplantation (HCT) or solid organ transplantation (SOT). Although PTLD occurs rarely, it may be associated with poor outcomes. In most cases, PTLD is driven by Epstein-Barr virus (EBV) infection. Few studies have investigated the mutational landscape and gene expression profile of PTLD. In our study, we performed targeted deep sequencing and RNA-sequencing (RNA-Seq) on 16 cases of florid follicular hyperplasia (FFH) type PTLD and 15 cases of other PTLD types that include: ten monomorphic (M-PTLD), three polymorphic (P-PTLD), and two classic Hodgkin lymphoma type PTLDs (CHL-PTLD). Our study identified recurrent mutations in JAK3 in five of 15 PTLD cases and one of 16 FFH-PTLD cases, as well as 16 other genes that were mutated in M-PTLD, P-PTLD, CHL-PTLD and FFH-PTLD. Digital image analysis demonstrated significant differences in single cell area, major axis, and diameter when comparing cases of M-PTLD and P-PTLD to FFH-PTLD. No morphometric relationship was identified with regards to a specific genetic mutation. Our findings suggest that immune regulatory pathways play an essential role in PTLD, with the JAK/STAT pathway affected in many PTLDs.

Hypodiploid B-Lymphoblastic Leukemia Presenting as an Isolated Orbital Mass Prior to Systemic Involvement: A Case Report and Review of the Literature.

We describe a 4-year-old boy who presented with progressive right periorbital edema and proptosis, with no systemic symptoms, who was found to have B-lymphoblastic leukemia (B-ALL). Magnetic resonance imaging (MRI) showed an enhancing mass centered in the right superolateral extraconal orbit. Orbital biopsy was consistent with B-ALL (CD99, TdT, LCA cocktail, CD34, CD79, CD10, PAX5, MIB1 positive; CD3, CD20 negative). A subsequent bone marrow aspirate confirmed a diagnosis of B-ALL with 80% blasts by flow cytometry and haploid cytogenetic findings. The patient improved clinically after chemotherapy. There are seven cases previously reported in the literature with hematogenous orbital masses at initial presentation of childhood ALL, but all with systemic symptoms or an abnormal complete blood count (CBC) at presentation. Our case is the first report in which an orbital mass preceded detectable systemic or laboratory evidence of ALL. This patient highlights the importance of differentiating benign causes of eyelid swelling from malignant ones.

Primary Central Nervous System Lymphomas: A Diagnostic Overview of Key Histomorphologic, Immunophenotypic, and Genetic Features.

Primary central nervous system lymphoma (PCNSL) is a rare form of extranodal non-Hodgkin lymphoma that primarily arises in the brain, spinal cord, leptomeninges, and vitreoretinal compartment of the eye. The term is sometimes used interchangeably with primary central nervous system diffuse large B-cell lymphoma (PCNS DLBCL) because DLBCL comprises a great majority (90-95%) of PCNSL. Although rare, other types of lymphomas can be seen in the central nervous system (CNS), and familiarity with these entities will help their recognition and further workup in order to establish the diagnosis. The latter is especially important in the case of PCNSL where procurement of diagnostic specimen is often challenging and yields scant tissue. In this review, we will discuss the most common types of primary lymphomas that can be seen in the CNS with emphasis on the diagnostic histomorphologic, immunophenotypic, and molecular genetic features. The differential diagnostic approach to these cases and potential pitfalls will also be discussed.