Paraspinal ganglioneuroma in the proband of a large family with mild cutaneous manifestations of NF1, carrying a deepNF1intronic mutation

Maturation of metastases in peripheral neuroblastic tumors (neuroblastoma) of children

Peripheral neuroblastic tumors of childhood exhibit 3 principal neural crest lineages: primitive neuroblastoma, ganglioneuroblastoma, and ganglioneuroma. They are unique in undergoing maturation of neurons (ganglion cells) and Schwann cells, thereby recapitulating normal fetal neuronal development in the brain. Precision in estimating neurogenesis is enhanced by immunoreactivities of markers of neuronal maturation. Whether organ tissue factors in different sites of metastases influence rates of maturation and whether metastases are similar to their primary neuroblastic tumor are incompletely documented. Four young children, 1 with a mixed primary adrenal tumor and 3 with metastases were studied at surgery or autopsy. Immunocytochemical reactivities included microtubule-associated protein-2, synaptophysin, chromogranin-A, somatostatin, keratan sulfate, vimentin, S-100β protein, and PHOX2B. Primary tumors were non-uniform with regions of either poor or enhanced maturation. Both neuronal and Schwannian lineages were represented in each tumor type but differed in proportions. Bi- or multi-nucleated ganglion cells matured equal to mononuclear forms. Ganglion cell maturation was similar in metastases regardless of the target organ. Metastases resembled primary tumors. Immunocytochemical markers of neuronal and of Schwann cell maturation provide greater diagnostic precision to supplement histological criteria. Interval between diagnosis of primary tumor and metastases, metastatic target tissues, and chemotherapy over an interval of time do not appear to influence neuroblastic or Schwann cell differentiation.

Analysis of 200 unrelated individuals with a constitutional NF1 deep intronic pathogenic variant reveals that variants flanking the alternatively spliced NF1 exon 31 [23a] cause a classical neurofibromatosis type 1 phenotype while altering predominantly NF1 isoform type II

Neurofibromatosis type 1 results from loss-of-function NF1 pathogenic variants (PVs). Up to 30% of all NF1 PVs disrupt mRNA splicing, including deep intronic variants. Here, we retrospectively investigated the spectrum of NF1 deep intronic PVs in a cohort of 8,090 unrelated individuals from the University of Alabama at Birmingham (UAB) dataset with a molecularly confirmed neurofibromatosis type 1. All variants were identified through their effect on the NF1 transcript, followed by variant characterization at the DNA-level. A total of 68 distinct variants, which were ≥ 20 nucleotides away from the closest exon-intron junction, were identified in 2.5% unrelated individuals with NF1 (200/8,090). Nine different pathogenic splice variants, identified in 20 probands, led to exonization of different parts of intron 30 [23.2] or 31 [23a]. The two major NF1 transcript isoforms, distinguished by the absence (type I) or presence (type II) of the alternatively spliced cassette exon 31 [23a], are equally expressed in blood in control individuals without NF1 or NF1-affected individuals carrying their PV not in the introns flanking exon 31 [23a]. By fragment and cloning analysis we demonstrated that the exonization of intron 31 [23a] sequences due to deep intronic PV predominantly affects the NF1 isoform II. Seven additional (likely) pathogenic NF1 deep intronic variants not observed in the UAB dataset were found by classification of 36 variants identified by a literature search. Hence, the unique list of these 75 deep intronic (likely) PVs should be included in any comprehensive NF1 testing strategy.

Clinical outcomes following resection of paraspinal ganglioneuromas: a case series of 15 patients

OBJECTIVE

Paraspinal ganglioneuromas are rare tumors that arise from neural crest tissue and can cause morbidity via compression of adjacent organs and neurovascular structures. The authors investigated a case series of these tumors treated at their institution to determine clinical outcomes following resection.

METHODS

A retrospective review of a prospectively collected cohort of consecutive, pathology-confirmed, surgically treated paraspinal ganglioneuromas from 2001 to 2019 was performed at a tertiary cancer center.

RESULTS

Fifteen cases of paraspinal ganglioneuroma were identified: 47% were female and the median age at the time of surgery was 30 years (range 10-67 years). Resected tumors included 9 thoracic, 1 lumbar, and 5 sacral, with an average maximum tumor dimension of 6.8 cm (range 1-13.5 cm). Two patients had treated neuroblastomas that matured into ganglioneuromas. One patient had a secretory tumor causing systemic symptoms. Surgical approaches were anterior (n = 11), posterior (n = 2), or combined (n = 2). Seven (47%) and 5 (33%) patients underwent gross-total resection (GTR) or subtotal resection with minimal residual tumor, respectively. The complication rate was 20%, with no permanent neurological deficits or deaths. No patient had evidence of tumor recurrence or progression after a median follow-up of 68 months.

CONCLUSIONS

Surgical approaches and extent of resection for paraspinal ganglioneuromas must be heavily weighed against the advantages of aggressive debulking and decompression given the complication risk of these procedures. GTR can be curative, but even patients without complete tumor removal can show evidence of excellent long-term local control and clinical outcomes.

Analysis of Pathogenic Pseudoexons Reveals Novel Mechanisms Driving Cryptic Splicing

Understanding pre-mRNA splicing is crucial to accurately diagnosing and treating genetic diseases. However, mutations that alter splicing can exert highly diverse effects. Of all the known types of splicing mutations, perhaps the rarest and most difficult to predict are those that activate pseudoexons, sometimes also called cryptic exons. Unlike other splicing mutations that either destroy or redirect existing splice events, pseudoexon mutations appear to create entirely new exons within introns. Since exon definition in vertebrates requires coordinated arrangements of numerous RNA motifs, one might expect that pseudoexons would only arise when rearrangements of intronic DNA create novel exons by chance. Surprisingly, although such mutations do occur, a far more common cause of pseudoexons is deep-intronic single nucleotide variants, raising the question of why these latent exon-like tracts near the mutation sites have not already been purged from the genome by the evolutionary advantage of more efficient splicing. Possible answers may lie in deep intronic splicing processes such as recursive splicing or poison exon splicing. Because these processes utilize intronic motifs that benignly engage with the spliceosome, the regions involved may be more susceptible to exonization than other intronic regions would be. We speculated that a comprehensive study of reported pseudoexons might detect alignments with known deep intronic splice sites and could also permit the characterisation of novel pseudoexon categories. In this report, we present and analyse a catalogue of over 400 published pseudoexon splice events. In addition to confirming prior observations of the most common pseudoexon mutation types, the size of this catalogue also enabled us to suggest new categories for some of the rarer types of pseudoexon mutation. By comparing our catalogue against published datasets of non-canonical splice events, we also found that 15.7% of pseudoexons exhibit some splicing activity at one or both of their splice sites in non-mutant cells. Importantly, this included seven examples of experimentally confirmed recursive splice sites, confirming for the first time a long-suspected link between these two splicing phenomena. These findings have the potential to improve the fidelity of genetic diagnostics and reveal new targets for splice-modulating therapies.

Real-world experience with management of spinal ganglioneuroma: long-term follow-up observations of 31 cases

INTRODUCTION

Spinal ganglioneuroma (GN) is the most benign neoplasm of neuroblastic origin. There is little knowledge about spinal GN because of sporadic cases reported. The objective of this study is to describe the clinical manifestations and long-term follow-up outcomes of spinal GN after consecutive treatment.

METHODS

The clinical and follow-up data of 31 patients with spinal GN receiving consecutive treatment in our institute are retrospectively analyzed.

RESULTS

The mean age of the 31 patients was 40.39 ± 14.8 years. They were diagnosed with spinal GN and received surgical treatment in our institution between February 2012 and August 2019. Of them, 22 (71%) patients presented preoperative neurological symptoms. The mean duration from symptom onset to surgery was 19.76 ± 49.59 months. Eighteen patients received complete surgical resection and 13 patients received subtotal excision. In addition, radicotomy was performed simultaneously after sophisticated consideration in 19 patients. The follow-up period averaged 64.13 ± 22.67 months. The preoperative neurological dysfunction was improved significantly during the follow-up period in all cases. No local recurrence or malignant transformation has occurred so far.

CONCLUSION

Spinal GN is a rare but benign neoplasm, and the origin of spinal GN remains controversial. With our experience, we propose that the origin of spinal GN from dorsal root ganglion should be equally considered as its counterpart of sympathetic ganglion. Complete resection is the preferred surgical strategy to avoid malignant events and recurrence. And the close postoperative follow-up observations are warranted.

A Novel Phenotype of Germline Pathogenic Variants in MAX: Concurrence of Pheochromocytoma and Ganglioneuroma in a Chinese Family and Literature Review

Background:MYC associated factor X (MAX) is a tumor suppressor gene and has been identified as one of the pathogenic genes of hereditary pheochromocytoma (PCC). To date, there have been no reports of ganglioneuroma (GN) with MAX variants. Case Presentation: The proband was a 45-years-old Chinese female with paroxysmal hypertension and palpitations who had undergone adrenalectomy for PCC 14 years ago. Her plasma free normetanephrine and 24-h urinary norepinephrine excretion were significantly increased, and abdominal computed tomography (CT) revealed an irregular mass in the left adrenal region, suggesting a recurrence of PCC. The mass was surgically removed and pathologically diagnosed as PCC with lymph node metastasis. The proband's son suffered from paroxysmal hypertension and palpitations. His plasma free metanephrine levels were normal. CT revealed a mass in the right adrenal. The tumor was surgically removed, and the pathological diagnosis was GN. Genetic testing of peripheral blood DNA revealed that the proband and her son had germline pathogenic MAX variant c.C97T, p.Arg33Ter, while proband's parents did not have MAX variants. Tumor DNA sequencing showed the same MAX variant (c.C97T, p.Arg33Ter) in PCC of the proband and GN of her son, both with retention of heterozygosity. Immunohistochemistry demonstrated loss of MAX protein expression in most tumor cells in PCC of the proband and some Schwannian cells in GN of the proband's son. Conclusion: We report a family with a new clinical phenotype of germline pathogenic variants in MAX who developed both PCC and GN. Germline pathogenic variants in MAX may contribute to the development of GN. Our findings suggest that it is not just paternally inherited MAX variants that can cause tumors.

Recent developments in brain tumor predisposing syndromes

The etiologies of brain tumors are in the most cases unknown, but improvements in genetics and DNA screening have helped to identify a wide range of brain tumor predisposition disorders. In this review we are discussing some of the most common predisposition disorders, namely: neurofibromatosis type 1 and 2, schwannomatosis, rhabdoid tumor predisposition disorder, nevoid basal cell carcinoma syndrome (Gorlin), tuberous sclerosis complex, von Hippel-Lindau, Li-Fraumeni and Turcot syndromes. Recent findings from the GLIOGENE collaboration and the newly identified glioma causing gene POT1, will also be discussed. Genetics. We will describe these disorders from a genetic and clinical standpoint, focusing on the difference in clinical symptoms depending on the underlying gene or germline mutation. Central nervous system (CNS) tumors. Most of these disorders predispose the carriers to a wide range of symptoms. Herein, we will focus particularly on tumors affecting the CNS and discuss improvements of targeted therapy for the particular disorders.