Programmed cell death ligand 1 expression in aggressive pediatric non-Hodgkin lymphomas: frequency, genetic mechanisms, and clinical significance.

Programmed cell death 1 (PD-1) and programmed cell death ligand 1 (PD-L1) are immunomodulatory molecules overexpressed in lymphomas and are promising immunotherapy targets for hematologic malignancies. However, studies of PD-1/PD-L1 overexpression and their clinical significance in aggressive pediatric non-Hodgkin lymphomas (NHL) are limited. We assessed PD-1/PD-L1 overexpression using immunohistochemistry in 68 aggressive pediatric NHL: ALK-positive anaplastic large cell lymphoma (ALK+ ALCL, n=8), Burkitt lymphoma (BL, n=27), and large B-cell lymphoma (LBCL) de novo LBCL, n=22 and diffuse LBCL arising as monomorphic post-transplant lymphoproliferative disorder [PTLD-DLBCL], n=11. In LBCL, correlations between PD-L1 overexpression and Epstein-Barr virus (EBV) status, cell of origin, stage, nodal status, overall survival (OS), and event-free survival (EFS) were examined. The genetic mechanisms of PD-L1 overexpression were investigated using targeted next-generation sequencing (NGS) and cytogenetic data. All ALK+ ALCL samples, 50.0% of de novo LBCL (11/22), 72.7% of PTLD-DLBCL (8/11), and no BL overexpressed PD-L1. Overexpressed PD-L1 correlated with EBV positivity (P=0.033) in LBCL and lower EFS in de novo LBCL (P=0.017). NGS of select LBCL revealed distinct somatic mutations and an ultra-hypermutated PTLD-DLBCL. Most cases with 9p24.1 copy gains overexpressed PD-L1 although some cases had no discernible genetic drivers of PD-L1 overexpression. Overexpressed PD-L1 is common in pediatric LBCL, associated with EBV positivity and 9p24.1 gains, and may have prognostic significance in de novo LBCL. Furthermore, diverse molecular mechanisms for PD-L1 overexpression in aggressive pediatric NHL can occur. Thus, additional studies exploring the therapeutic and prognostic significance and molecular mechanisms of PD-L1 overexpression in aggressive pediatric NHL are warranted.

Hemophagocytic lymphohistiocytosis associated with influenza A (H1N1) infection in a patient with chronic lymphocytic leukemia: an autopsy case report and review of the literature.

H1N1 influenza A virus can trigger fatal hemophagocytic lymphohistiocytosis in immunocompromised patients and in immunocompetent hosts, usually children. We present a case of a 50-year-old man with low-burden chronic lymphocytic leukemia who had sudden reactivation of his leukemia triggered by influenza A (H1N1) infection with hemophagocytic lymphohistiocytosis during the 2009 H1N1 pandemic. His rapid course was complicated by acute respiratory distress syndrome with diffuse alveolar damage, a 6-fold rise in lymphocyte count, disseminated intravascular coagulation, and, ultimately, cardiac arrest. Major findings at autopsy included: bilateral H1N1 pneumonitis with diffuse alveolar damage, intra-alveolar pulmonary hemorrhage, pulmonary microthromboemboli, pulmonary hemorrhagic infarction, hemophagocytic lymphohistiocytosis in multiple locations, and diffuse chronic lymphocytic leukemia. Hemophagocytic lymphohistiocytosis is a serious and often fatal condition, which may be primary or secondary. It may be associated with high-grade lymphoproliferative malignancies, especially in patients with therapy-related leukocytopenia, but only rarely is it seen in uncomplicated chronic lymphocytic leukemia. Hemophagocytic lymphohistiocytosis may be triggered by a variety of infections (viral, fungal, bacterial and parasitic), but H1N1 influenza A-associated hemophagocytic lymphohistiocytosis is often rapidly fatal, especially in children. This adult patient's clinical presentation with low tumor burden and leukocytosis is thus unique. We review the recently published autopsy findings in fatal influenza A (H1N1) infection and the association with resultant secondary hemophagocytic lymphohistiocytosis.

Genomic trajectory in leukemogenesis of myeloproliferative neoplasms: a case report.

BACKGROUND: We report a patient with Essential Thrombocythemia (ET), subsequently diagnosed with concurrent myeloid and lymphoid leukemia. Generally, the molecular mechanisms underlying leukemic transformation of Philadelphia-negative myeloproliferative neoplasms (Ph-MPN) are poorly understood. Risk of transformation to acute myelogenous leukemia (AML) is low; transformation to both AML and acute lymphoblastic leukemia (ALL) is extremely low. Genetic defects, including allele burden, order of mutation acquisition, clonal heterogeneity and epigenetic mechanisms are important contributors to disease acceleration. CASE PRESENTATION: A 78-year-old Caucasian female originally treated for stable ET, underwent disease acceleration and transition to myeloid sarcoma and B-cell ALL. Genomic reconstruction based on targeted sequencing revealed the presence of a large del(5q) in all three malignancies and somatic driver mutations: TET2, TP53, SF3B1, and ASXL1 at high allele frequency. We propose that the combination of genetic and molecular abnormalities led to hematopoietic stem cell (HSC) injury and disease progression through sub-clone branching. We hypothesize that ancestral reconstruction of genomic data is a useful tool to uncover subclonal events leading to transformation. CONCLUSIONS: The use of ancestral reconstruction of genomic data sheds light on the unique clinical scenario described in this case report. By determining the mutational profile of tumors at several timepoints and deducing the most parsimonious relationship between them, we propose a reconstruction of their origin. We propose that blast progression originated from subclonal events with malignant potential, which coexisted with but did not originate from JAK2 p.V617F-positive ET. We conclude that the application of genomic reconstruction enhances our understanding of leukemogenesis by identifying the timing of molecular events, potentially leading to better chemotherapy choices as well as the development of new targeted therapies.

Somatic mutations in children with GATA2-associated myelodysplastic syndrome who lack other features of GATA2 deficiency.

Approximately 10% of children with primary myelodysplastic syndrome (MDS) have germ line GATA2 mutations, leading to the proposal that all children with primary MDS and certain cytogenetic findings, including monosomy 7, be tested for germ line GATA2 mutations regardless of family history or other clinical features associated with GATA2 deficiency. In adults with familial GATA2-MDS, those with somatic mutations in ASXL1 experience rapid disease progression to acute myeloid leukemia (AML) and poor prognosis after stem cell transplantation; however, the prevalence of somatic mutations in primary pediatric GATA2-MDS is unclear. Here, we studied a cohort of 8 pediatric patients with MDS and lacking additional GATA2-associated clinical features or significant family history and identified heterozygous germ line GATA2 mutations in 5 patients, including 1 with a normal karyotype. For those with GATA2-MDS, we screened for somatic mutations in genes with prognostic relevance in AML/MDS, using a targeted next-generation sequencing panel. Although no somatic mutations in ASXL1 were observed, somatic mutations were found in RUNX1, SETBP1, IKZF1, and CRLF2. One subject with deleterious mutations in RUNX1, SETBP1, and IKZF1 rapidly progressed to AML with disease that was refractory to treatment. Our findings confirm the importance of GATA2 testing in primary pediatric MDS, even in the absence of other clinical features of GATA2 deficiency. Further, similar to what has been observed in adults with GATA2-MDS, somatic mutations with potential prognostic effect occur in children with MDS associated with mutations in GATA2.

Childhood nodal marginal zone lymphoma with unusual clinicopathologic and cytogenetic features for the pediatric variant: a case report.

Nodal marginal zone lymphoma (NMZL) is a B-cell lymphoma that shares morphologic and immunophenotypic features with extranodal and splenic marginal zone lymphomas but lacks extranodal or splenic involvement at presentation. NMZL occurs mostly in adults with no sex predilection, at advanced stage (III or IV), with frequent relapses and a high incidence of tumoral genetic abnormalities including trisomies 3 and 18 and gain of 7q. Pediatric NMZL, however, is a rare but distinct variant of NMZL with characteristic features including male predominance, asymptomatic and localized (stage I) disease, low relapse rates with excellent outcomes, and a lower incidence of essentially similar genetic aberrations compared to adult NMZL. Here we describe a unique case of childhood NMZL with unusual clinicopathologic features for the pediatric variant including generalized lymphadenopathy, high-stage disease with persistence after therapy, unusual immunophenotype (CD5, CD23, and BCL6 positive), and unique chromosomal abnormalities including monosomy 20 and add(10)(p11.2).