How Many Tests Does It Take to Diagnose a Triple-Hit B-Lymphoblastic Lymphoma? (Hint, It's A Lot).

B-lymphoblastic leukemia/lymphoma (B-ALL/LBL) is a precursor B-cell neoplasm that often harbors specific cytogenetic/molecular abnormalities with distinctive clinical, phenotypic, and prognostic characteristics. Subcategorization of B-ALL/LBL therefore requires extensive cytogenetic and/or molecular testing to determine the appropriate classification and therapeutic interventions for these patients. Herein, we present a case of a 17-year-old young woman diagnosed with B-LBL harboring not only an IGH::MYC rearrangement but also BCL2 and BCL6 rearrangements (so-called "triple-hit") and somatic biallelic TP53 inactivation. MYC rearrangements are relatively rare in B-ALL/LBL, and the identification of a "triple-hit" elicited an initial diagnostic dilemma. However, a multimodal approach allowed for the classification of this complex case and helped guide selection of an appropriate therapeutic regimen.

Multicenter study of pediatric Epstein-Barr virus-negative monomorphic post solid organ transplant lymphoproliferative disorders.

BACKGROUND: Pediatric Epstein-Barr virus-negative monomorphic post solid organ transplant lymphoproliferative disorder [EBV(-)M-PTLD] comprises approximately 10% of M-PTLD. No large multi-institutional pediatric-specific reports on treatment and outcome are available. METHODS: A multi-institutional retrospective review of solid organ recipients diagnosed with EBV(-)M-PTLD aged ≤21 years between 2001 and 2020 in 12 centers in the United States and United Kingdom was performed, including demographics, staging, treatment, and outcomes data. RESULTS: Thirty-six patients were identified with EBV(-)M-PTLD. Twenty-three (63.9%) were male. Median age (range) at transplantation, diagnosis of EBV(-)M-PTLD, and interval from transplant to PTLD were 2.2 years (0.1-17), 14 years (3.0-20), and 8.5 years (0.6-18.3), respectively. Kidney (n = 17 [47.2%]) and heart (n = 13 [36.1%]) were the most commonly transplanted organs. Most were Murphy stage III (n = 25 [69.4%]). Lactate dehydrogenase was elevated in 22/34 (64.7%) and ≥2 times upper limit of normal in 11/34 (32.4%). Pathological diagnoses included diffuse large B-cell lymphoma (n = 31 [86.1%]) and B-non-Hodgkin lymphoma (B-NHL) not otherwise specified (NOS) (n = 5 [13.9%]). Of nine different regimens used, the most common were: pediatric mature B-NHL-specific regimen (n = 13 [36.1%]) and low-dose cyclophosphamide, prednisone, and rituximab (n = 9 [25%]). Median follow-up from diagnosis was 3.0 years (0.3-11.0 years). Three-year event-free survival (EFS) and overall survival (OS) were 64.8% and 79.9%, respectively. Of the seven deaths, six were from progressive disease. CONCLUSIONS: EFS and OS were comparable to pediatric EBV(+) PTLD, but inferior to mature B-NHL in immunocompetent pediatric patients. The wide range of therapeutic regimens used directs our work toward developing an active multi-institutional registry to design prospective studies. PLAIN LANGUAGE SUMMARY: Pediatric Epstein-Barr virus-negative monomorphic post solid organ transplant lymphoproliferative disorders (EBV(-)M-PTLD) have comparable outcomes to EBV(+) PTLD, but are inferior to diffuse large B-cell lymphoma in immunocompetent pediatric patients. The variety of treatment regimens used highlights the need to develop a pediatric PTLD registry to prospectively evaluate outcomes. The impact of treatment regimen on relapse risk could not be assessed because of small numbers. In the intensive pediatric B-non-Hodgkin lymphoma chemoimmunotherapy group, 11 of 13 patients remain alive in complete remission after 0.6 to 11 years.

Burkitt lymphoma after solid-organ transplant: Treatment and outcomes in the paediatric PTLD collaborative.

Burkitt lymphoma arising in paediatric post-solid-organ transplantation-Burkitt lymphoma (PSOT-BL) is a clinically aggressive malignancy and a rare form of post-transplant lymphoproliferative disorder (PTLD). We evaluated 35 patients diagnosed with PSOT-BL at 14 paediatric medical centres in the United States. Median age at organ transplantation was 2.0 years (range: 0.1-14) and age at PSOT-BL diagnosis was 8.0 years (range: 1-17). All but one patient had late onset of PSOT-BL (≥2 years post-transplant), with a median interval from transplant to PSOT-BL diagnosis of 4.0 years (range: 0.4-12). Heart (n = 18 [51.4%]) and liver (n = 13 [37.1%]) were the most frequently transplanted organs. No patients had loss of graft or treatment-related mortality. A variety of treatment regimens were used, led by intensive Burkitt lymphoma-specific French-American-British/Lymphomes Malins B (FAB/LMB), n = 13 (37.1%), and a low-intensity regimen consisting of cyclophosphamide, prednisone and rituximab (CPR) n = 12 (34.3%). Median follow-up was 6.7 years (range: 0.5-17). Three-year event-free and overall survival were 66.2% and 88.0%, respectively. Outcomes of PSOT-BL patients receiving BL-specific intensive regimens are comparable to reported BL outcomes in immunocompetent children. Multi-institutional collaboration is feasible and provides the basis of prospective data collection to determine the optimal treatment regimen for PSOT-BL.

High-dose AraC is essential for the treatment of ML-DS independent of postinduction MRD: results of the COG AAML1531 trial.

Myeloid leukemia in children with Down syndrome (ML-DS) is associated with young age and somatic GATA1 mutations. Because of high event-free survival (EFS) and hypersensitivity of the leukemic blasts to chemotherapy, the prior Children's Oncology Group protocol ML-DS protocol (AAML0431) reduced overall treatment intensity but lacking risk stratification, retained the high-dose cytarabine course (HD-AraC), which was highly associated with infectious morbidity. Despite high EFS of ML-DS, survival for those who relapse is rare. AAML1531 introduced therapeutic risk stratification based on the previously identified prognostic factor, measurable residual disease (MRD) at the end of the first induction course. Standard risk (SR) patients were identified by negative MRD using flow cytometry (<0.05%) and did not receive the historically administered HD-AraC course. Interim analysis of 114 SR patients revealed a 2-year EFS of 85.6% (95% confidence interval [CI], 75.7-95.5), which was significantly lower than for MRD- patients treated with HD-AraC on AAML0431 (P = .0002). Overall survival at 2 years was 91.0% (95% CI, 83.8-95.0). Twelve SR patients relapsed, mostly within 1 year from study entry and had a 1-year OS of 16.7% (95% CI, 2.7-41.3). Complex karyotypes were more frequent in SR patients who relapsed compared with those who did not (36% vs 9%; P = .0248). MRD by error-corrected sequencing of GATA1 mutations was piloted in 18 SR patients and detectable in 60% who relapsed vs 23% who did not (P = .2682). Patients with SR ML-DS had worse outcomes without HD-AraC after risk classification based on flow cytometric MRD.

Characterization of HLH-like manifestations as a CRS variant in patients receiving CD22 CAR T cells.

Chimeric antigen receptor (CAR) T-cell toxicities resembling hemophagocytic lymphohistiocytosis (HLH) occur in a subset of patients with cytokine release syndrome (CRS). As a variant of conventional CRS, a comprehensive characterization of CAR T-cell-associated HLH (carHLH) and investigations into associated risk factors are lacking. In the context of 59 patients infused with CD22 CAR T cells where a substantial proportion developed carHLH, we comprehensively describe the manifestations and timing of carHLH as a CRS variant and explore factors associated with this clinical profile. Among 52 subjects with CRS, 21 (40.4%) developed carHLH. Clinical features of carHLH included hyperferritinemia, hypertriglyceridemia, hypofibrinogenemia, coagulopathy, hepatic transaminitis, hyperbilirubinemia, severe neutropenia, elevated lactate dehydrogenase, and occasionally hemophagocytosis. Development of carHLH was associated with preinfusion natural killer(NK) cell lymphopenia and higher bone marrow T-cell:NK cell ratio, which was further amplified with CAR T-cell expansion. Following CRS, more robust CAR T-cell and CD8 T-cell expansion in concert with pronounced NK cell lymphopenia amplified preinfusion differences in those with carHLH without evidence for defects in NK cell mediated cytotoxicity. CarHLH was further characterized by persistent elevation of HLH-associated inflammatory cytokines, which contrasted with declining levels in those without carHLH. In the setting of CAR T-cell mediated expansion, clinical manifestations and immunophenotypic profiling in those with carHLH overlap with features of secondary HLH, prompting consideration of an alternative framework for identification and management of this toxicity profile to optimize outcomes following CAR T-cell infusion.

Comprehensive molecular and clinical characterization of NUP98 fusions in pediatric acute myeloid leukemia.

NUP98 fusions comprise a family of rare recurrent alterations in AML, associated with adverse outcomes. In order to define the underlying biology and clinical implications of this family of fusions, we performed comprehensive transcriptome, epigenome, and immunophenotypic profiling of 2,235 children and young adults with AML and identified 160 NUP98 rearrangements (7.2%), including 108 NUP98-NSD1 (4.8%), 32 NUP98-KDM5A (1.4%) and 20 NUP98-X cases (0.9%) with 13 different fusion partners. Fusion partners defined disease characteristics and biology; patients with NUP98-NSD1 or NUP98-KDM5A had distinct immunophenotypic, transcriptomic, and epigenomic profiles. Unlike the two most prevalent NUP98 fusions, NUP98-X variants are typically not cryptic. Furthermore, NUP98-X cases are associated with WT1 mutations, and have epigenomic profiles that resemble either NUP98-NSD1 or NUP98-KDM5A. Cooperating FLT3-ITD and WT1 mutations define NUP98-NSD1, and chromosome 13 aberrations are highly enriched in NUP98-KDM5A. Importantly, we demonstrate that NUP98 fusions portend dismal overall survival, with the noteworthy exception of patients bearing abnormal chromosome 13 (clinicaltrials gov. Identifiers: NCT00002798, NCT00070174, NCT00372593, NCT01371981).

Pathologic, cytogenetic, and molecular features of acute myeloid leukemia with megakaryocytic differentiation: A report from the Children's Oncology Group.

BACKGROUND: Acute myeloid leukemia (AML) with megakaryocytic differentiation (AMkL) is a rare subtype of AML more common in children. Recent literature has identified multiple fusions associated with this type of leukemia. METHODS: Morphology, cytogenetics, and genomic sequencing were assessed in patients from Children's Oncology Group trials AAML0531 and AAML1031 with central-pathology review confirmed non-Down syndrome AMkL. The 5-year event-free survival (EFS), overall survival (OS), and RR were evaluated in these AMkL subcategories. RESULTS: A total of 107 cases of AMkL (5.5%) were included. Distinct fusions were identified in the majority: RBM15::MRTFA (20%), CBFA2T3::GLIS2 (16%), NUP98 (10%), KMT2A (7%), TEC::MLLT10 (2%), MECOM (1%), and FUS::ERG (1%); many of the remaining cases were classified as AMkL with (other) myelodysplasia-related changes (MRC). Very few cases had AML-associated somatic mutations. Cases with CBFA2T3::GLIS2 were enriched in trisomy 3 (p = .015) and the RAM phenotype, with associated high CD56 expression (p < .001). Cases with NUP98 fusions were enriched in trisomy 6 (p < .001), monosomy 13/del(13q) (p < .001), trisomy 21 (p = .026), and/or complex karyotypes (p = .026). While different 5-year EFS and OS were observed in AMkL in each trial, in general, those with CBFA2T3::GLIS2 or KMT2A rearrangements had worse outcomes compared to other AMkL, while those with RBM15::MRTFA or classified as AMkl-MRC fared better. AMkL with NUP98 fusions also had poor outcomes in the AAML1031 trial. CONCLUSION: Given the differences in outcomes, AMkL classification by fusions, cytogenetics, and morphology may be warranted to help in risk stratification and therapeutic options.

A Malignant Mimicker: Features of Kikuchi-Fujimoto Disease in the Pediatric Population.

BACKGROUND: Kikuchi-Fujimoto disease (KFD) is a rare, benign, and self-limited disease that presents with cervical lymphadenopathy and systemic symptoms. Histologic evaluation is often necessary to differentiate KFD from other entities. METHODS: Electronic medical records and diagnostic material were reviewed for 14 children diagnosed with KFD and 6 children diagnosed with infectious mononucleosis (IM) from 2013-2021. Four cases of KFD were further characterized using targeted DNA-based next-generation sequencing. RESULTS: Systemic symptoms were present in 86% (n = 12/14) of KFD patients, the most common being fever. Laboratory values worrisome for malignancy included cytopenia(s) (n = 9/12), elevated ESR and/or CRP (n = 9/12), elevated ferritin (n = 7/7), and elevated LDH (n = 7/10). Histologically, lymph nodes showed characteristic necrotic foci without neutrophils surrounded by MPO+ "crescentic" histiocytes. Immunoblasts and CD123+ plasmacytoid dendritic cells (pDCs) were also increased surrounding the necrosis. IM lymph nodes showed similar features when necrosis was present but increases in pDCs were patchy and rare neutrophils were seen in the necrotic foci. Molecular analysis of 4 KFD cases did not identify pathogenic variants. CONCLUSION: While the signs/symptoms of KFD are worrisome, there are pathologic features that help differentiate it from potential mimics. We did not identify characteristic molecular features to aid in the work-up of these cases.

Clinical, immunophenotypic and genomic findings of NK lymphoblastic leukemia: a study from the Bone Marrow Pathology Group.

Natural killer (NK) cells are lymphocytes of the native immune system that play a pivotal role in host defense and immune surveillance. While the conceptual view of NK-neoplasms is evolving, little is known about the rare NK lymphoblastic leukemia (NK-LL), which remains as a provisional entity in the 2016 WHO Classification. The goal of this study is to characterize NK-LL cases and compare with other CD56 co-expressing acute leukemias. We identified 105 cases, diagnosed as NK-LL (6), CD56+ acute undifferentiated leukemia (AUL) (6), CD56+ T-lymphoblastic leukemia (T-LL) (51), and CD56+ acute myeloid leukemia (AML) (42). Compared to AUL patients, NK-LL patients were significantly younger (p = 0.021) and presented with higher white blood cell (WBC) (p = 0.037) and platelet counts (p = 0.041). Flow cytometry showed more frequent expression of cytoplasmic CD3 (cCD3, p = 0.064) and CD33, (p = 0.065), while HLA-DR was significantly absent from NK-LL (p = 0.035) compared to AUL. Compared to T-ALL, NK-LL cases showed less frequent cCD3 (p = 0.002), CD4 (p = 0.051), and CD10 expression (p = 0.06). The frequency of abnormal karyotypes was similar between NK-LL, AUL, and T-ALL. The mutational profile differed in four leukemia groups, with a significance enrichment of NOTCH1 (p = 0.002), ETV6 (p = 0.002) and JAK3 (p = 0.02) mutations in NK-LL as compared to AML. As compared to T-ALL, NK-LL cases showed a higher number of total mutations (p = 0.04) and significantly more frequent ETV6 mutations (p = 0.004). Clinical outcome data showed differences in overall survival between all four groups (p = 0.0175), but no difference in event free survival (p = 0.246). In this largest study to date, we find that that NK-LL shows clinical presentation, immunophenotypic and molecular characteristics distinct from AUL, T-ALL, and AML. Our findings suggest NK-LL is a distinct acute leukemia entity and should be considered in the clinical diagnosis of acute leukemias of ambiguous lineage.

Lineage Switch in an Infant B-Lymphoblastic Leukemia With t(1;11)(p32;q23); KMT2A/EPS15, Following Blinatumomab Therapy.

We report a 6 month-old infant girl with t(1;11)(p32;q23), KMT2A/EPS15-rearranged B-acute lymphoblastic leukemia (B-ALL) that was refractory to traditional ALL-directed chemotherapy. Following administration of blinatumomab, she experienced lineage switch from B-ALL to acute myeloid leukemia (AML). Myeloid-directed chemotherapy resulted in clearance of AML by flow cytometry, though a residual CD19+ B-ALL population persisted (0.14%). Following bridging blinatumomab, the patient achieved B-ALL and AML remission, as measured by flow cytometry. The patient subsequently underwent allogeneic hematopoietic stem cell transplant. Unfortunately, she relapsed with CD19+ B-ALL one-month post-transplantation. Next generation sequencing study of IGH/IGL using ClonoSEQ® analysis detected 3 dominant sequences all present in her original B-ALL, lineage switched AML, and post-transplant relapsed B-ALL, though the latter showed an additional 4 sequences, three of which were present at low abundance in the original diagnostic sample. The presence of the same clones throughout her disease course suggests cellular reprogramming and differentiation following chemotherapy and immunotherapy. This is the first reported case of lineage switch of B-ALL with t(1;11) and also the first report of a lineage switch case that used ClonoSEQ® to define the clonality of the original B-ALL, lineage switched AML, and relapsed B-ALL.

Effects of Tumor Necrosis Factor Alpha Inhibitors on Lymph Node and Ileocecal Mucosa-Associated Lymphoid Tissue Architecture in Patients With Inflammatory Bowel Disease.

BACKGROUND: Antitumor necrosis alpha (TNFα) therapy is often used in the management of patients with inflammatory bowel disease (IBD) and may have effects on lymphoid tissue architecture and function. The goal of our study was to characterize the effects of TNFα inhibitors on mesenteric lymph node and mucosa-associated lymphoid tissue in patients with IBD. METHODS: We examined lymphoid tissue morphology in IBD patients treated with TNFα inhibitors compared to untreated controls. Intestinal resections from 19 patients (10 anti-TNFα treated and 9 controls) were reviewed. Immunohistochemistry for CD21, CD20, and CD3 was performed on ileocecal valve lymphoid tissue and mesenteric lymph nodes from the resection specimens to assess follicular architecture. RESULTS: Relative to control groups, TNFα-treated groups showed less preserved germinal center architecture, evidenced by lower overall semiquantitative scores for follicular architecture. Likewise, the percentage of secondary follicles to total follicles was decreased in patients treated with TNFα blockade. CONCLUSIONS: Our results suggest that TNFα inhibitors may play a role in disruption of lymphoid germinal center architecture in patients with IBD. Awareness of this disrupted lymphoid morphology when examining histologic sections from patients with IBD treated with TNFα inhibitors may prevent unnecessary studies to exclude a lymphoproliferative disorder.

IRF4 translocation status in pediatric follicular and diffuse large B-cell lymphoma patients enrolled in Children's Oncology Group trials.

Large B-cell lymphoma with IRF4 rearrangement is a provisional entity in the 2017 World Health Organization classification. In order to characterize these lymphomas in children from the United States, IRF4 FISH and immunohistochemical stains were performed on 32 follicular lymphoma and diffuse large B-cell lymphoma (DLBCL) from Children's Oncology Group studies. Two DLBCLs (6%) had IRF4 rearrangements, one involving the ileocecal valve and another involving the tonsil and cerebrospinal fluid. Both cases had strong, diffuse IRF4/MUM1 immunohistochemical staining, which may be a pathologic clue to the diagnosis. Reclassification of these cases may have prognostic and therapeutic implications.

Bone Marrow Morphology Associated With Germline RUNX1 Mutations in Patients With Familial Platelet Disorder With Associated Myeloid Malignancy.

Germline mutations in RUNX1 result in autosomal dominant familial platelet disorder with associated myeloid malignancy (FPDMM). To characterize the hematopathologic features associated with a germline RUNX1 mutation, we reviewed a total of 42 bone marrow aspirates from 14 FPDMM patients, including 24 cases with no cytogenetic clonal abnormalities, and 18 with clonal karyotypes or leukemia. We found that all aspirate smears had ≥10% atypical megakaryocytes, predominantly characterized by small forms with hypolobated and eccentric nuclei, and forms with high nuclear-to-cytoplasmic ratios. Core biopsies showed variable cellularity and variable numbers of megakaryocytes with similar features to those in the aspirates. Granulocytic and/or erythroid dysplasia (≥10% cells per lineage) were present infrequently. Megakaryocytes with separate nuclear lobes were increased in patients with myelodysplastic syndrome (MDS) and acute leukemia. Comparison to an immune thrombocytopenic purpura cohort confirms increased megakaryocytes with hypolobated eccentric nuclei in FPDMM patients. As such, patients with FPDMM often have atypical megakaryocytes with small hypolobated and eccentric nuclei even in the absence of clonal cytogenetic abnormalities; these findings are related to the underlying RUNX1 germline mutation and not diagnostic of MDS. Isolated megakaryocytic dysplasia in patients with unexplained thrombocytopenia should raise the possibility of an underlying germline RUNX1 mutation.

An analysis of blastic plasmacytoid dendritic cell neoplasm with translocations involving the MYC locus identifies t(6;8)(p21;q24) as a recurrent cytogenetic abnormality.

AIMS: Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is an aggressive neoplasm with leukaemic features and frequent skin involvement. Translocations involving the MYC locus have been recently identified as recurrent cytogenetic abnormalities in this entity. The aim of this study was to assess the clinicopathological, immunophenotypic and genetic features in MYC-rearranged BPDCN cases. METHODS AND RESULTS: Pathology archives from six major institutes were queried for cases of BPDCN with 8q24 MYC translocations, and two cases were identified. A literature review identified 14 cases. Clinicopathological features, immunophenotype and cytogenetic and molecular data were reviewed. In these 16 MYC-rearranged cases, the median age at diagnosis was 70.5 years, and there was a male predominance. Whereas all cases showed marrow involvement, skin lesions (62.5%) and lymphadenopathy (50%) were variably seen. The median survival was 11 months. The median percentage of blasts in peripheral blood was 9%. All cases showed expression of CD4, with 10 of 16 being positive for CD56. HLA-DR, CD123, TCL1 and CD303 were positive in all cases tested. Cytogenetic analysis revealed a single recurrent translocation partner of MYC at 6p21 in 11 cases (69%), whereas four cases showed different MYC translocation partners (2p12, Xq24, 3p25, and 14q32). Interestingly, the group of patients with t(6;8)(p21;q24) showed an older median age at diagnosis (74 years) and a remarkably shorter median survival (3 months). CONCLUSIONS: Translocations involving the 8q24 MYC locus more frequently manifest as t(6;8)(p21;q24), and, given its association with specific clinicopathological features suggesting even more aggressive behaviour, t(6;8)(p21;q24) indicate a genetically defined subgroup within BPDCN.

Classification of Preterm Birth With Placental Correlates.

Premature birth lacks a widely accepted classification that unites features of the clinical presentation with placental pathology. To further explore associations between the clinical categories of preterm birth and placental histology, 109 infants with gestational age <34 weeks and birth weight <2000 g were selected and, based on electronic records, were classified into preterm birth categories of preterm labor, prelabor premature rupture of membranes, preeclampsia, indicated preterm birth for maternal factors (other than preeclampsia), indicated preterm birth for fetal factors, and the clinical diagnosis of abruption. Corresponding placentas were analyzed for gross and microscopic variables, with findings grouped into categories of amniotic fluid infection, lymphocytic inflammation, maternal vascular malperfusion, and fetal vascular malperfusion. Placental features of maternal vascular malperfusion were pervasive in all preterm birth categories and were commonly associated with amniotic fluid infection and lymphocytic inflammation. Features of maternal vascular malperfusion were significantly associated with preterm birth due to preeclampsia, and amniotic fluid infection was highly associated with prelabor preterm rupture of membranes. Findings of lymphocytic inflammation were significantly increased in cases of abruption. Laminar decidual necrosis was present in all cases of abruption. Placentas from multiple gestations had significantly less histologic findings compared to singletons. Given that 75% of placentas demonstrated at least 1 feature of maternal vascular malperfusion despite different clinical presentations, seemingly different pathologies such as ascending amniotic fluid infection or lymphocytic inflammation may be mechanistically related to processes established early in pregnancy. The concept of "uterine ischemia" may be too simplistic to account for all of the changes attributed to maternal vascular malperfusion in the preterm placenta.

How Rare Is an Oral Presentation of Myeloid Sarcoma in the Infant?

Myeloid sarcomas of the oral cavity are exceedingly rare. This report describes a recent case, and reviews the literature. This case report serves three purposes: 1) to demonstrate that the use of an intraoral biopsy can diagnose severe systemic disease; 2) to remind practitioners to be cognizant of less common diagnoses in the differential diagnosis of facial swelling; and 3) to contribute a case of myeloid sarcoma that was confirmed by flow cytometry to the published data.

A study of the mutational landscape of pediatric-type follicular lymphoma and pediatric nodal marginal zone lymphoma.

Pediatric-type follicular lymphoma and pediatric marginal zone lymphoma are two of the rarest B-cell lymphomas. These lymphomas occur predominantly in the pediatric population and show features distinct from their more common counterparts in adults: adult-type follicular lymphoma and adult-type nodal marginal zone lymphoma. Here we report a detailed whole-exome deep sequencing analysis of a cohort of pediatric-type follicular lymphomas and pediatric marginal zone lymphomas. This analysis revealed a recurrent somatic variant encoding p.Lys66Arg in the transcription factor interferon regulatory factor 8 (IRF8) in 3 of 6 cases (50%) of pediatric-type follicular lymphoma. This specific point mutation was not detected in pediatric marginal zone lymphoma or in adult-type follicular lymphoma. Additional somatic point mutations in pediatric-type follicular lymphoma were observed in genes involved in transcription, intracellular signaling, and cell proliferation. In pediatric marginal zone lymphoma, no recurrent mutation was identified; however, somatic point mutations were observed in genes involved in cellular adhesion, cytokine regulatory elements, and cellular proliferation. A somatic variant in AMOTL1, a recurrently mutated gene in splenic marginal zone lymphoma, was also identified in a case of pediatric marginal zone lymphoma. The overall non-synonymous mutational burden was low in both pediatric-type follicular lymphoma and pediatric marginal zone lymphoma (4.6 mutations per exome). Altogether, these findings support a distinctive genetic basis for pediatric-type follicular lymphoma and pediatric marginal zone lymphoma when compared with adult subtypes and to one another. Moreover, identification of a recurrent point mutation in IRF8 provides insight into a potential driver mutation in the pathogenesis of pediatric-type follicular lymphoma with implications for novel diagnostic or therapeutic strategies.

Heme oxygenase-1 confers protection and alters T-cell populations in a mouse model of neonatal intestinal inflammation.

BACKGROUND: Necrotizing enterocolitis (NEC), an intestinal inflammatory disease affecting premature infants, is associated with low regulatory T (Treg) to effector T (Teff) cell ratios. We recently demonstrated that heme oxygenase-1 (HO-1) deficiency leads to increased NEC development. Here, we investigated the effects of HO-1 on T-cell proportions in a murine NEC-like injury model. METHODS: Intestinal injury was induced in 7-d-old wild-type (WT) or HO-1 heterozygous (HO-1 Het) pups by formula-feeding every 4 h for 24-78 h by oral gavage and exposures to 5%O2. Controls remained breastfed. HO-1 was induced in WT pups by administering heme preinjury induction. Lamina propria T cells were identified by flow cytometry. For adoptive transfer studies, WT splenic/thymic Tregs were injected intraperitoneally into HO-1 Het pups 12-24 h preinduction. RESULTS: Het mice showed increased intestinal injury and decreased Treg/Teff ratios. Genes for pattern recognition (Toll-like receptor-4, C-reactive protein, MyD88) and neutrophil recruitment increased in Het pups after NEC induction. Inducing intestinal HO-1 decreased NEC scores and incidence, and increased Treg/Teff ratios. Moreover, adoptive transfer of Tregs from WT to HO-1 Het pups decreased NEC scores and incidence and restored Treg/Teff ratios. CONCLUSION: HO-1 can change Treg proportions in the lamina propria of young mice under inflammatory conditions, which might, in part, confer intestinal protection.

Mutations in mitochondrial histidyl tRNA synthetase HARS2 cause ovarian dysgenesis and sensorineural hearing loss of Perrault syndrome.

Perrault syndrome is a genetically heterogeneous recessive disorder characterized by ovarian dysgenesis and sensorineural hearing loss. In a nonconsanguineous family with five affected siblings, linkage analysis and genomic sequencing revealed the genetic basis of Perrault syndrome to be compound heterozygosity for mutations in the mitochondrial histidyl tRNA synthetase HARS2 at two highly conserved amino acids, L200V and V368L. The nucleotide substitution creating HARS2 p.L200V also created an alternate splice leading to deletion of 12 codons from the HARS2 message. Affected family members thus carried three mutant HARS2 transcripts. Aminoacylation activity of HARS2 p.V368L and HARS2 p.L200V was reduced and the deletion mutant was not stably expressed in mammalian mitochondria. In yeast, lethality of deletion of the single essential histydyl tRNA synthetase HTS1 was fully rescued by wild-type HTS1 and by HTS1 p.L198V (orthologous to HARS2 p.L200V), partially rescued by HTS1 p.V381L (orthologous to HARS2 p.V368L), and not rescued by the deletion mutant. In Caenorhabditis elegans, reduced expression by RNAi of the single essential histydyl tRNA synthetase hars-1 severely compromised fertility. Together, these data suggest that Perrault syndrome in this family was caused by reduction of HARS2 activity. These results implicate aberrations of mitochondrial translation in mammalian gonadal dysgenesis. More generally, the relationship between HARS2 and Perrault syndrome illustrates how causality may be demonstrated for extremely rare inherited mutations in essential, highly conserved genes.

Unicentric Castleman Disease: Updates and Novel Insights Into Spindle Cell Proliferations and Aggressive Forms of a Localized Disease.

Castleman Disease (CD) is a rare lymphoproliferative disorder that can be separated into two primary forms: Unicentric Castleman disease (UCD) and multicentric Castleman disease (MCD). UCD is localized, while MCD is systemic. Though UCD generally has a favorable prognosis following surgical resection, more aggressive forms of this disease have been identified, including cases associated with dendritic and spindle cell proliferation. Genetic analysis has deepened our understanding of UCD. Despite advancements in better understanding the pathophysiology of UCD, challenges persist in the diagnosis, management, and treatment due to its rarity and heterogeneity. Here, we review current knowledge on UCD, highlighting the epidemiology, clinical presentation, diagnostic criteria, and treatment options while emphasizing the need for further research and innovation in therapeutic strategies.