Weaver syndrome and neuroblastoma

Correlation between large rearrangements and patient phenotypes in NF1 deletion syndrome: an update and review

About 5-10% of neurofibromatosis type 1 (NF1) patients exhibit large genomic germline deletions that remove the NF1 gene and its flanking regions. The most frequent NF1 large deletion is 1.4 Mb, resulting from homologous recombination between two low copy repeats. This "type-1" deletion is associated with a severe clinical phenotype in NF1 patients, with several phenotypic manifestations including learning disability, a much earlier development of cutaneous neurofibromas, an increased tumour risk, and cardiovascular malformations. NF1 adjacent co-deleted genes could act as modifier loci for the specific clinical manifestations observed in deleted NF1 patients. Furthermore, other genetic modifiers (such as CNVs) not located at the NF1 locus could also modulate the phenotype observed in patients with large deletions. In this study, we analysed 22 NF1 deletion patients by genome-wide array-CGH with the aim (1) to correlate deletion length to observed phenotypic features and their severity in NF1 deletion syndrome, and (2) to identify whether the deletion phenotype could also be modulated by copy number variations elsewhere in the genome. We then review the role of co-deleted genes in the 1.4 Mb interval of type-1 deletions, and their possible implication in the main clinical features observed in this high-risk group of NF1 patients.

Synchronous T-lymphoblastic lymphoma and neuroblastoma in a 3-yr-old with novel germline SMARCA4 and EZH2 variants

T-lymphoblastic lymphoma (T-LLy) is the most common lymphoblastic lymphoma in children and often presents with a mediastinal mass. Lymphomatous suprarenal masses are possible but rare. Here, we discuss the case of a previously healthy 3-yr-old male who presented with mediastinal T-LLy with bilateral suprarenal masses. Following initial treatment, surgical biopsy of persisting adrenal masses revealed bilateral neuroblastoma (NBL). A clinical genetics panel for germline cancer predisposition did not identify any pathogenic variants. Combination large panel (864 genes) profiling analysis in the context of a precision oncology study revealed two novel likely pathogenic heterozygous variants: SMARCA4 c.1420-1G > T p.? and EZH2 c.1943G > C p.(Ile631Phefs*44). Somatic analysis revealed potential second hits/somatic variants in EZH2 (in the T-LLy) and a segmental loss in Chromosome 19p encompassing SMARCA4 (in the NBL). Synchronous cancers, especially at a young age, warrant genetic evaluation for cancer predisposition; enrollment in a precision oncology program assessing germline and tumor DNA can fulfill that purpose, particularly when standard first-line genetic testing is negative and in the setting of tumors that are not classic for common cancer predisposition syndromes.

Splicing-Disrupting Mutations in Inherited Predisposition to Solid Pediatric Cancer

The prevalence of hereditary cancer in children was estimated to be very low until recent studies suggested that at least 10% of pediatric cancer patients carry a germline mutation in a cancer predisposition gene. A significant proportion of pathogenic variants associated with an increased risk of hereditary cancer are variants affecting splicing. RNA splicing is an essential process involved in different cellular processes such as proliferation, survival, and differentiation, and alterations in this pathway have been implicated in many human cancers. Hereditary cancer genes are highly susceptible to splicing mutations, and among them there are several genes that may contribute to pediatric solid tumors when mutated in the germline. In this review, we have focused on the analysis of germline splicing-disrupting mutations found in pediatric solid tumors, as the discovery of pathogenic splice variants in pediatric cancer is a growing field for the development of personalized therapies. Therapies developed to correct aberrant splicing in cancer are also discussed as well as the options to improve the diagnostic yield based on the increase in the knowledge in splicing.

Laparoscopic approach of pediatric adrenal tumors

PURPOSE

To analyze the role of laparoscopic surgery for the management of pediatric adrenal tumors (AT).

METHODS

Retrospective analysis of children diagnosed with AT, operated laparoscopically during 2003-2020. The strategy differed according to tumor extension. AT < 6 cm were resected. Locally advanced tumors (L2) or > 6 cm were biopsied.

RESULTS

N = 28. Complete tumor resection (R0) in 20 (71%), tumor biopsy in 8 (R2). Age (median): 28.8 months (2 months-18 years). 14/28 left-sided, 2 bilateral. Median operating time: 78 min (45-180). Mean tumor size (for resections): 4 cm (2.5-6). Tumor pathology: neuroblastoma (n = 17), Ganglioneuroma (n = 7), Adrenocortical carcinoma (n = 1), Osteosarcoma metastasis (n = 1), Pheochromocytoma (n = 1), Venous malformation (n = 1). Mean hospital stay: 2.5 days (1-3). Mean follow up: 65.5 months (24-192). Overall survival and event-free survival were 86 and 75%, respectively (5 years event-free survival for neuroblastoma: 33% [intermediate risk], 16.6% [high risk]. No surgery-related mortality.

CONCLUSION

Laparoscopic surgery for adrenal tumors is safe. Laparoscopic biopsy is useful for unresectable tumors when a percutaneous approach is not possible. With the proposed selection criteria, the laparoscopic approach should be the first option for resection of small and localized AT in pediatrics.

Diagnostic Approach to Macrocephaly in Children

Macrocephaly affects up to 5% of the pediatric population and is defined as an abnormally large head with an occipitofrontal circumference (OFC) >2 standard deviations (SD) above the mean for a given age and sex. Taking into account that about 2-3% of the healthy population has an OFC between 2 and 3 SD, macrocephaly is considered as "clinically relevant" when OFC is above 3 SD. This implies the urgent need for a diagnostic workflow to use in the clinical setting to dissect the several causes of increased OFC, from the benign form of familial macrocephaly and the Benign enlargement of subarachnoid spaces (BESS) to many pathological conditions, including genetic disorders. Moreover, macrocephaly should be differentiated by megalencephaly (MEG), which refers exclusively to brain overgrowth, exceeding twice the SD (3SD-"clinically relevant" megalencephaly). While macrocephaly can be isolated and benign or may be the first indication of an underlying congenital, genetic, or acquired disorder, megalencephaly is most likely due to a genetic cause. Apart from the head size evaluation, a detailed family and personal history, neuroimaging, and a careful clinical evaluation are crucial to reach the correct diagnosis. In this review, we seek to underline the clinical aspects of macrocephaly and megalencephaly, emphasizing the main differential diagnosis with a major focus on common genetic disorders. We thus provide a clinico-radiological algorithm to guide pediatricians in the assessment of children with macrocephaly.

Genetic Predisposition to Solid Pediatric Cancers

Progresses over the past years have extensively improved our capacity to use genome-scale analyses—including high-density genotyping and exome and genome sequencing—to identify the genetic basis of pediatric tumors. In particular, exome sequencing has contributed to the evidence that about 10% of children and adolescents with tumors have germline genetic variants associated with cancer predisposition. In this review, we provide an overview of genetic variations predisposing to solid pediatric tumors (medulloblastoma, ependymoma, astrocytoma, neuroblastoma, retinoblastoma, Wilms tumor, osteosarcoma, rhabdomyosarcoma, and Ewing sarcoma) and outline the biological processes affected by the involved mutated genes. A careful description of the genetic basis underlying a large number of syndromes associated with an increased risk of pediatric cancer is also reported. We place particular emphasis on the emerging view that interactions between germline and somatic alterations are a key determinant of cancer development. We propose future research directions, which focus on the biological function of pediatric risk alleles and on the potential links between the germline genome and somatic changes. Finally, the importance of developing new molecular diagnostic tests including all the identified risk germline mutations and of considering the genetic predisposition in screening tests and novel therapies is emphasized.

Genetic variation associated with childhood and adult stature and risk of MYCN-amplified neuroblastoma

Background

Neuroblastoma is the most common pediatric solid tumor. MYCN‐amplification is an important negative prognostic indicator and inherited genetic contributions to risk are incompletely understood. Genetic determinants of stature increase risk of several adult and childhood cancers, but have not been studied in neuroblastoma despite elevated neuroblastoma incidence in children with congenital overgrowth syndromes.

Methods

We investigated the association between genetic determinants of height and neuroblastoma risk in 1538 neuroblastoma cases, stratified by MYCN‐amplification status, and compared to 3390 European‐ancestry controls using polygenic scores for birth length (five variants), childhood height (six variants), and adult height (413 variants). We further examined the UK Biobank to evaluate the association of known neuroblastoma risk loci and stature.

Results

An increase in the polygenic score for childhood stature, corresponding to a ~0.5 cm increase in pre‐pubertal height, was associated with greater risk of MYCN‐amplified neuroblastoma (OR = 1.14, P = .047). An increase in the polygenic score for adult stature, corresponding to a ~1.7 cm increase in adult height attainment, was associated with decreased risk of MYCN‐amplified neuroblastoma (OR = 0.87, P = .047). These associations persisted in case‐case analyses comparing MYCN‐amplified to MYCN‐unamplified neuroblastoma. No polygenic height scores were associated with MYCN‐unamplified neuroblastoma risk. Previously identified genome‐wide association study hits for neuroblastoma (N = 10) were significantly enriched for association with both childhood (P = 4.0 × 10⁻³) and adult height (P = 8.9 × 10⁻³) in >250 000 UK Biobank study participants.

Conclusions

Genetic propensity to taller childhood height and shorter adult height were associated with MYCN‐amplified neuroblastoma risk, suggesting that biological pathways affecting growth trajectories and pubertal timing may contribute to MYCN‐amplified neuroblastoma etiology.

Polycomb Repressor Complex 2 in Genomic Instability and Cancer

Polycomb repressor complexes PRC1 and PRC2 regulate chromatin compaction and gene expression, and are widely recognized for their fundamental contributions to developmental processes. Herein, we summarize the existing evidence and molecular mechanisms linking PRC-mediated epigenetic aberrations to genomic instability and malignancy, with a particular focus on the role of deregulated PRC2 in tumor suppressor gene expression, the DNA damage response, and the fidelity of DNA replication. We also discuss some of the recent advances in the development of pharmacological and dietary interventions affecting PRC2, which point to promising applications for the prevention and management of human malignancies.

EZH2 mutation in an adolescent with Weaver syndrome developing acute myeloid leukemia and secondary hemophagocytic lymphohistiocytosis

Weaver syndrome is an overgrowth syndrome characterized by pre- and postnatal overgrowth with distinctive craniofacial appearance. Mutations in the enhancer of zeste homolog 2 (EZH2) gene were found to cause Weaver syndrome, and have been associated with hematologic malignancies, including acute myeloid leukemia (AML). We present the first report of a patient with Weaver syndrome, who developed AML and harbored an EZH2 mutation. The clinical course of the 16-year-old female adolescent patient was complicated by a secondary hemophagocytic lymphohistiocytosis. Genomic DNA was isolated from bone marrow cells at AML diagnosis. Polymerase chain reactions were performed with primers covering all exons of the EZH2 gene. We found a novel heterozygous EZH2 mutation within exon 5 that caused an amino acid change from proline to leucine at position 132 (p.Pro132Leu) within the catalytic D1 domain. Analysis of a remission sample also showed this mutation, indicating a germline mutation. It remains to be elucidated whether EZH2 mutations contribute to disease severity in specific AML cases.

Neuroblastoma in a Patient With Spinal Muscular Atrophy Type I: Is It Just a Coincidence?

Spinal muscular atrophy is an autosomal recessive disorder characterized by progressive degeneration of anterior horn cells of the spinal cord resulting in hypotonia, skeletal muscle atrophy, and weakness. Herein, we report a 4-month-old male infant who presented to our hospital with an abdominal mass that was diagnosed as neuroblastoma and spinal muscular atrophy type I. We would like to discuss the course and differential diagnosis with an algorithm leading to the diagnosis in this peculiar patient. To our knowledge, coexistence of spinal muscular atrophy type I and neuroblastoma is defined for the first time in the literature.

Generalized overgrowth syndromes with prenatal onset

Children with generalized overgrowth syndromes are large at birth, or have excessive postnatal growth. Many of these syndromes are associated with an increase in neoplasia. Consideration of the possibility of overgrowth syndrome in a pediatric patient who presents with increased growth parameters, variable malformations and neurodevelopmental phenotype, and distinctive features, is important for medical management, reproductive counseling, and tumor surveillance for some of the disorders. This review describes the clinical features and surveillance recommendations for the common generalized overgrowth syndromes the pediatrician may encounter. It also provides a glimpse into advances of recent years in understanding the molecular mechanisms responsible for the disrupted growth regulation in these disorders.

Weaver syndrome and EZH2 mutations: Clarifying the clinical phenotype

Weaver syndrome, first described in 1974, is characterized by tall stature, a typical facial appearance, and variable intellectual disability. In 2011, mutations in the histone methyltransferase, EZH2, were shown to cause Weaver syndrome. To date, we have identified 48 individuals with EZH2 mutations. The mutations were primarily missense mutations occurring throughout the gene, with some clustering in the SET domain (12/48). Truncating mutations were uncommon (4/48) and only identified in the final exon, after the SET domain. Through analyses of clinical data and facial photographs of EZH2 mutation-positive individuals, we have shown that the facial features can be subtle and the clinical diagnosis of Weaver syndrome is thus challenging, especially in older individuals. However, tall stature is very common, reported in >90% of affected individuals. Intellectual disability is also common, present in ~80%, but is highly variable and frequently mild. Additional clinical features which may help in stratifying individuals to EZH2 mutation testing include camptodactyly, soft, doughy skin, umbilical hernia, and a low, hoarse cry. Considerable phenotypic overlap between Sotos and Weaver syndromes is also evident. The identification of an EZH2 mutation can therefore provide an objective means of confirming a subtle presentation of Weaver syndrome and/or distinguishing Weaver and Sotos syndromes. As mutation testing becomes increasingly accessible and larger numbers of EZH2 mutation-positive individuals are identified, knowledge of the clinical spectrum and prognostic implications of EZH2 mutations should improve.

Acute lymphoblastic leukemia in Weaver syndrome

Weaver syndrome comprises pre- and postnatal overgrowth, accelerated osseous maturation, characteristic craniofacial appearance and developmental delay; it is a generally sporadic disorder, although autosomal dominant inheritance has been reported. Some of the manifestations characterize both the Weaver and Sotos syndrome, and distinction between the two is mainly by clinical examination and molecular testing. Most of the patients with Sotos syndrome have NSD1 gene deletions or mutations; however, the molecular basis of most of the Weaver syndrome patients is unknown. Patients with overgrowth syndromes have an increased frequency of tumors; the risk in Sotos syndrome patients has been estimated to be about 2-3%, with leukemia and lymphoma accounting for 44% of the malignancies. We report on a 4(1/2)-year-old girl with typical Weaver syndrome who developed acute lymphoblastic leukemia, an association not previously reported, and review the reported cases of Weaver syndrome patients who developed malignancies. Malignancy in Weaver syndrome has been reported previously in six patients. While searching the literature for all reported cases with Weaver syndrome and counting the cases with malignancy, we found that the frequency of tumors or hematologic malignancy was 10.9%. This is likely to be an overestimate, biased by failure to report cases without tumors and by over-reporting cases with this rare association. While the presence of acute lymphoblastic leukemia in our patient might be incidental, we cannot exclude a possible causative association between Weaver syndrome and hematologic malignancy.