Clonal Hematopoiesis Without Malignant Transformation Lasting Over 2 Years in a 9-Year-old Boy, Following Treatment for Acute Lymphocytic Leukemia

Children with acute lymphocytic leukemia rarely develop secondary hematological neoplasms. A 5-year-old boy was diagnosed with standard-risk precursor B-cell acute lymphocytic leukemia. The patient exhibited aberrant chromosomal changes in the bone marrow at 6 months postchemotherapy: 46,XY,der(6) t(1;6)(q12;p22) dup(6)(p22p12)[15]. Clinically, the patient has sustained complete remission and has not developed myeloid malignancy over the subsequent period (27 mo). The cytogenetic aberration was observed in 11% of CD34+ cells isolated from the bone marrow. We infer that the abnormal clone acquires self-renewal potency, differentiation, and growth advantage. Further long-term observation is needed to determine the nature of this cytogenetic aberration.

Malignant melanoma in a 12-year-old boy 17 months after completing hepatoblastoma treatment

BACKGROUND

Melanoma is rare as a secondary malignant neoplasm among childhood cancer survivors.

CASE

We report a case of a 12-year-old boy who developed malignant melanoma with systemic metastases 17 months after completing treatment for hepatoblastoma. The diagnosis was made unexpectedly based on a bone marrow examination. The patient did not respond to immune checkpoint inhibitor therapy and died 6 weeks after being diagnosed with melanoma. Whole-exome sequencing to examine 103 genes associated with cancer predisposition did not identify any germ-line variants.

CONCLUSION

This case study provides a unique example of melanoma in a childhood cancer survivor following hepatoblastoma treatment but does not identify any candidate variant to link hepatoblastoma and melanoma.

Eculizumab treatment in paediatric patients diagnosed with aHUS after haematopoietic stem cell transplantation: a HSCT-TMA case series from Japanese aHUS post-marketing surveillance

Haematopoietic stem-cell transplantation (HSCT)-associated thrombotic microangiopathy (HSCT-TMA) is a serious complication with high mortality. Accumulating evidence suggests that complement dysregulation is potentially involved in the development of HSCT-TMA. We retrospectively analysed the clinical characteristics and outcomes of thirteen paediatric patients who were diagnosed with atypical haemolytic uremic syndrome and treated with eculizumab to manage HSCT-TMA during post-marketing surveillance in Japan. The median time from HSCT to TMA was 31 days (Interquartile range, IQR;21-58) and the median doses of eculizumab was three (IQR;2-5). Seven patients (54%) were alive at the last follow-up while six died due to complications related to HSCT. Six of seven survivors initiated eculizumab after insufficient response to plasma therapy. Following eculizumab treatment, median platelet counts and LDH levels in all survivors significantly improved and renal function improved in 4/7 patients. All survivors possessed potential risk factors of complement overactivation. During the follow-up period after eculizumab discontinuation (median;111.5 days, IQR;95-555), no TMA recurrence was observed. In this analysis, eculizumab showed benefit in over half of this paediatric patient population. Ongoing clinical studies are expected to optimize the treatment regimen of terminal complement pathway inhibitor, and it may become a therapeutic option for paediatric HSCT-TMA in the future.

Six Years of Disease-free Survival After a Second Cord Blood Transplantation for Recurrent Acute Lymphocytic Leukemia in a Child With Down Syndrome

Outcomes are extremely poor in Down syndrome-associated acute lymphocytic leukemia, particularly in recurrent cases. A 2-year-old boy with Down syndrome-associated acute lymphocytic leukemia achieved complete remission after standard chemotherapy. However, he experienced recurrence twice in the bone marrow and central nervous system. Salvage treatments included whole-brain/whole-spine irradiation. Thereafter, the patient received a second cord blood transplantation after the reduced-intensity conditioning. The graft was characterized by killer cell immunoglobulin-like receptor ligands mismatch. The patient has subsequently survived for 6.5 years without recurrence. We speculate that killer cell immunoglobulin-like receptor ligand-mismatched cord blood transplantation enhanced the graft-versus-leukemia effect through natural killer cells, and conferred long-term remission.

Breakpoint analysis for cytogenetically balanced translocation revealed unexpected complex structural abnormalities and suggested the position effect for MEF2C

Many disease-causing genes have been identified by determining the breakpoints of balanced chromosomal translocations. Recent progress in genomic analysis has accelerated the analysis of chromosomal translocation-breakpoints at the nucleotide level. Using a long-read whole-genome sequence, we analyzed the breakpoints of the cytogenetically balanced chromosomal translocation t(5;15)(q21;26.3), which was confirmed to be of de novo origin, in a patient with a neurodevelopmental disorder. The results showed complex rearrangements with seven fragments consisting of five breakpoint-junctions (BJs). Four of the five BJs showed microhomologies of 1-3-bp, and only one BJ displayed a signature of blunt-end ligation, indicating chromothripsis as the underlying mechanism. Although the BJs did not disrupt any disease-causing gene, the clinical features of the patient were compatible with MEF2C haploinsufficiency syndrome. Complex rearrangements were located approximately 2.5-Mb downstream of MEF2C. Therefore, position effects were considered the mechanism of the occurrence of MEF2C haploinsufficiency syndrome.

Variant spectrum of PIEZO1 and KCNN4 in Japanese patients with dehydrated hereditary stomatocytosis

Hereditary stomatocytosis (HSt) is a type of congenital hemolytic anemia caused by abnormally increased cation permeability of erythrocyte membranes. Dehydrated HSt (DHSt) is the most common subtype of HSt and is diagnosed based on clinical and laboratory findings related to erythrocytes. PIEZO1 and KCNN4 have been recognized as causative genes, and many related variants have been reported. We analyzed the genomic background of 23 patients from 20 Japanese families suspected of having DHSt using a target capture sequence and identified pathogenic/likely pathogenic variants of PIEZO1 or KCNN4 in 12 families.

Cord Blood Transplantation in 2 Infants Presenting Monosomy 7 Clonal Hematopoiesis: SAMD9 / SAMD9L Germline Mutation

Recently, germline mutations in SAMD9 and SAMD9L were increasingly found in children with monosomy 7. We report the outcomes in 2 infants with the SAMD9/SAMD9L variant, who presented with anemia and thrombocytopenia (patient 1), and neutropenia and nonsymptomatic white-matter-encephalopathy (patient 2). Both patients received cord blood transplantation and experienced critical post-cord blood transplantation adverse events; patients 1 and 2 developed fulminant engraftment syndrome and life-threatening graft-versus-host disease, respectively. Of note, selective loss of chromosome 7 in bone marrow-derived CD34 + cells was inferred.

Interstitial microdeletions of 3q26.2q26.31 in two patients with neurodevelopmental delay and distinctive features

Interstitial microdeletions in the long arm of chromosome 3 are rare. In this study, we identified two patients with approximately 5-Mb overlapping deletions in the 3q26.2q26.31 region. Both patients showed neurodevelopmental delays, congenital heart defects, and distinctive facial features. One of them showed growth deficiency and brain abnormalities, as shown on a magnetic resonance imaging scan. Haploinsufficiency of NLGN1 and FNDC3B present in the common deletion region was considered to be responsible for neurodevelopmental delay and the distinctive features, respectively. The possibility of unmasked variants in PLD1 was considered and analyzed, but no possible pathogenic variant was found, and the mechanism of the congenital heart defects observed in the patients is unknown. Because 3q26.2q26.31 deletions are rare, more information is required to establish genotype-phenotype correlations associated with microdeletions in this region.

Long-read sequence analysis for clustered genomic copy number aberrations revealed architectures of intricately intertwined rearrangements

Most chromosomal aberrations revealed by chromosomal microarray testing (CMA) are simple; however, very complex chromosomal structural rearrangements can also be found. Although the mechanism of structural rearrangements has been gradually revealed, not all mechanisms have been elucidated. We analyzed the breakpoint-junctions (BJs) of two or more clustered copy number variations (CNVs) in the same chromosome arms to understand their conformation and the mechanism of complex structural rearrangements. Combining CMA with long-read whole-genome sequencing (WGS) analysis, we successfully determined all BJs for the clustered CNVs identified in four patients. Multiple CNVs were intricately intertwined with each other, and clustered CNVs in four patients were involved in global complex chromosomal rearrangements. The BJs of two clustered deletions identified in two patients showed microhomologies, and their characteristics were explained by chromothripsis. In contrast, the BJs in the other two patients, who showed clustered deletions and duplications, consisted of blunt-end and nontemplated insertions. These findings could be explained only by alternative nonhomologous end-joining, a mechanism related to polymerase theta. All the patients had at least one inverted segment. Three patients showed cryptic aberrations involving a disruption and a deletion/duplication, which were not detected by CMA but were first identified by WGS. This result suggested that complex rearrangements should be considered if clustered CNVs are observed in the same chromosome arms. Because CMA has potential limitations in genotype-phenotype correlation analysis, a more detailed analysis by whole genome examination is recommended in cases of suspected complex structural aberrations.

BRAFV600E-positive cells as molecular markers of bone marrow disease in pediatric Langerhans cell histiocytosis

Not available.

Multiple Immunofluorescence Imaging Analysis Reveals Differential Expression of Disialogangliosides GD3 and GD2 in Neuroblastomas

BACKGROUND

Peripheral neuroblastic tumors (pNTs) are the most common childhood extracranial solid tumors. There are several therapeutic strategies targeting disialoganglioside GD2. Disialoganglioside GD3 has become a potential target. However, the mechanism by which pNTs express GD3 and GD2 remains unclear. We investigated the combined expression status of GD3 and GD2 in pNTs and delineated their clinicopathological values.

METHODS

GD3 and GD2 expression was examined in pNT tissue samples (n = 35) using immunohistochemistry and multiple immunofluorescence imaging.

RESULTS

GD3 and GD2 expression was positive in 32/35 and 25/35 samples, respectively. Combinatorial analysis of GD3 and GD2 expression in neuroblastoma showed that both were heterogeneously expressed from cell to cell. There were higher numbers of GD3-positive and GD2-negative cells in the low-risk group than in the intermediate-risk (P = 0.014) and high-risk (P = 0.009) groups. Cases with high proportions of GD3-positive and GD2-negative cells were associated with the International Neuroblastoma Staging System stage (P = 0.004), Children's Oncology Group risk group (P = 0.001), and outcome (P = 0.019) and tended to have a higher overall survival rate.

CONCLUSION

We demonstrated that neuroblastomas from low-risk patients included more GD3-positive and GD2-negative cells than those from high-risk patients. Clarifying the heterogeneity of neuroblastoma aids in better understanding the biological characteristics and clinical behavior.

Case Report: Successful Treatment With Anti-C5 Monoclonal Antibody in a Japanese Adolescent Who Developed Thrombotic Microangiopathy After Autologous Bone Marrow Transplantation for Malignant Lymphoma

BACKGROUND

Transplant-associated thrombotic microangiopathy (TA-TMA) is a serious complication of bone marrow transplantation (BMT). Recently, abnormalities in the complement system have been identified in the pathogenesis of TA-TMA, and there are series of reports stating that anti-C5 monoclonal antibody (eculizumab) is effective in patients with high levels of the membrane attack complex (C5b-9).

CASE PRESENTATION

A 12-year-old boy underwent autologous BMT after receiving high-dose chemotherapy for malignant lymphoma. The patient was engrafted on day 19 after transplantation; however, hemolytic anemia and non-immune thrombocytopenia persisted, and haptoglobin decreased on day 46. Moreover, on day 83, the patient developed pulmonary hemorrhage, hypertension, severe proteinuria, hematuria, and acute kidney injury (AKI). Pulmonary bleeding stopped with daily platelet transfusion and hemostatic agents, but reappeared on day 100. Based on the presence of destruction of red blood cells, elevated lactate dehydrogenase levels, negative direct and indirect Coombs tests, normal ADAMTS13 levels, hemolytic anemia, non-immune thrombocytopenia, and AKI, the patient was diagnosed with systemic TA-TMA and we initiated plasma exchange (PE) and continuous hemodialysis for AKI. High C5b-9 levels were identified at the start of the series of PE, therefore we decided to administer eculizumab. After three courses of eculizumab, no pulmonary hemorrhage was observed, and anemia, thrombocytopenia, renal dysfunction, hematuria, and proteinuria all tended to improve. Three years after transplantation, the patient is alive and does not require eculizumab.

DISCUSSION

Eculizumab is a humanized monoclonal antibody that binds complement protein C5, preventing cleavage C5 and the formation of C5b-9. In this case, TA-TMA could not be controlled with PE alone. We therefore decided to use eculizumab relatively early based on the high C5b-9 level and could resolve the momentum of TA-TMA.

CONCLUSION

In previous reports, TA-TMA typically occurred in early post-allogeneic BMT of patients with lymphoma or in post-autologous BMT of patients with neuroblastoma and was treated with eculizumab. We here reported that eculizumab could be successful treatment for TA-TMA in post-autologous BMT of patient with lymphoma.

Prognostic value of the revised International Prognostic Scoring System five-group cytogenetic abnormality classification for the outcome prediction of hematopoietic stem cell transplantation in pediatric myelodysplastic syndrome

Cytogenetic abnormalities are a major risk factor for relapse after hematopoietic stem cell transplantation (HSCT) for myelodysplastic syndrome (MDS). We aimed to evaluate the value of the five-group cytogenetic classification according to the revised International Prognostic Scoring System (R-IPSS) for predicting the outcome after HSCT in pediatric patients with MDS. We retrospectively analyzed the Japanese registration data of 242 pediatric patients with MDS. According to the R-IPSS classification, 112 (45.5%) patients had good, 55 (22.7%) had intermediate, 64 (26.4%) had poor, and 11 (4.6%) had very poor cytogenetics. The 5-year overall survival (5yOS) was 72%, 69%, 59%, and 30% in the good, intermediate, poor, and very poor cytogenetic subgroups (p = 0.026), respectively. The very good, good, and intermediate subgroups were grouped into a "standard" subgroup and reclassified into three subgroups (standard, poor, and very poor). Patients with very poor risk had worse 5yOS (hazard ratio 2.17, 95% confidence interval (CI) 1.02-4.61; p = 0.04) and a much higher 5yCIR (hazard ratio 2.52, 95% CI 1.05-6.04; p = 0.04) than those of patients in the standard group in the multivariate analysis, indicating that very poor risk cytogenetic characteristics independently predicted worse outcome after HSCT in pediatric patients with MDS.

OTHR-02. MULTIMODALITY TREATMENT FOR CHILDREN WITH CENTRAL NERVOUS SYSTEM (CNS) TUMOR IN OUR INSTITUTE

BACKGROUND

The brain tumor has a highest mortality rate among childhood malignant tumors. Development of peripheral blood stem cell transplant combined chemotherapy and radiation therapy improved the survival rate of patients with pediatric brain tumor drastically late years. Because of its complicated treatment plan, neurosurgeons cannot readily manage these aggressive therapies which require minute whole body control including prevention of lethal infection due to bone marrow suppression. Even if such treatment is effective and patient survives, the aftereffects may reduce patient’s QOL.

PURPOSE

We report outcomes of the patients with CNS tumor after multimodality treatment. In addition, we introduce the activity contents by the in-hospital children brain tumor multi-disciplinary medical treatment team organized in March 2016.

METHODS

We retrospectively reviewed 29 patients (under 15 years old) diagnosed as CNS tumors with total of 43 tumor surgeries between January 2001 and December 2019.

RESULTS

The histopathological diagnoses were 7 germ cell tumor, 7 astrocytic tumor, 4 ependymal tumor, 4 medulloblastoma, 2 craniopharyngioma, 2 AT/RT and 3 others. The mean age at first surgery was 7.4 y.o. (range: 0.3–14.8). Both chemotherapy and radiation therapy were performed in 22 cases out of 29. There were 15 survivors (11 ambulant, 3 W/C, 1 bedridden), 12 deaths, 2 lost follow-ups. Mean follow-up period was 66 months (range: 1–206).

CONCLUSION

To improve outcomes, we hold on a regular basis of team meeting, discuss treatment plan, and share information. Recently, we also care issues of the patients, such as fertility and palliative medicine.

Unexplained Late-Onset Hemolytic Jaundice Preceded by High Fetal Hemoglobin Level in an Extremely Low Birth Weight Infant

BACKGROUND

Preterm infants sometimes have transient late-onset hemolytic jaundice; however, the etiology has yet to be determined.

CASE PRESENTATION

In our case, fetal hemoglobin (HbF) level increased significantly to 100% at 23 days of age. Levels of methemoglobin and carboxyhemoglobin also increased to 2.9% and 3.5%, respectively, following the elevated HbF level. At 26 days, hemolytic jaundice developed. No abnormality of red blood cell membranes and enzyme activities was found.

CONCLUSIONS

The etiology of late-onset hemolytic jaundice in preterm infants may associate with an impaired switching from HbF to adult hemoglobin (HbA) or reverse switching from HbA to HbF.

Prevalence of germline GATA2 and SAMD9/9L variants in paediatric haematological disorders with monosomy 7

Monosomy 7 (-7) occurs in various types of paediatric myeloid disorders and has a poor prognosis. Recent studies have demonstrated that patients with germline gain-of-function SAMD9/9L variants and loss-of-function GATA2 variants are prone to developing myelodysplastic syndrome (MDS) associated with -7. However, the prevalence of the genetic variants among paediatric haematologic disorders with -7 is unknown. The present study screened germline variants of GATA2 and SAMD9/9L in 25 patients with various types of paediatric haematological disorders associated with -7. The diagnoses of the 25 patients included MDS (n = 10), acute myeloid leukaemia (AML) and myeloid sarcomas (n = 9), juvenile myelomonocytic leukaemia (n = 3) and other disorders (n = 3). Seven patients with a germline pathogenic GATA2 variant were found. For SAMD9/9L screening, next-generation sequencing was used to detect low-abundance variants and found four novel germline variants. Functional analysis revealed that three out of the four variants showed growth-restricting capacity in vitro and thus, were judged to be pathogenic. Cases with GATA2 mutation tended to be older, compared to those with SAMD9/9L mutations. In conclusion, GATA2 and SAMD9/9L were sequenced in 25 patients with paediatric haematologic disorders associated with -7, and 40% of them were found to have some pathogenic germline variants in the three genes.

Tectal Low-Grade Glioma with H3 K27M Mutation

BACKGROUND

In the revised World Health Organization 2016 classification of central nervous system tumors, "diffuse midline glioma, H3 K27M-mutant" has been added as a new diagnostic entity. However, some confusion exists concerning this diagnostic entity because H3 K27M-mutant diffuse midline glioma is diagnosed with grade IV regardless of morphologic phenotype. Furthermore, the significance of H3 K27M mutation in tumors that aren't typical "diffuse midline glioma, H3 K27M-mutant," such as those with an unusual location and nontypical histology, remains unclear.

CASE DESCRIPTION

To elucidate further such unusual tumors, we describe here a rare case of pediatric low-grade glioma located in the tectum, which was morphologically a pilocytic astrocytoma (PA) with genetically H3 K27M mutation but no microvascular proliferation, necrosis, mitoses, or other genetic alterations, insofar as we were able to observe. At the latest follow-up, 28 months after surgery, radiotherapy, and chemotherapy, the patient was found to be free from any neurologic deficits and MRI demonstrated that the tumor was stable without tumor regrowth. This case might be identified as "diffuse midline glioma, H3 K27M-mutant", grade IV, when applying only the current World Health Organization 2016 classification. In addition, we discuss the morphologically benign gliomas harboring the H3 K27M mutation based on the literature.

CONCLUSIONS

We describe here a rare case and present a short literature review of circumscribed/nondiffuse gliomas, particularly in PA with H3 K27M mutation. However, the significance of H3 K27M mutation for PA remains unclear, so further studies and clinical data are needed to elucidate the biology and optimal treatment of such tumors.