Adenoid cystic carcinoma of the Bartholin's gland is underpinned by MYB- and MYBL1- rearrangements.

OBJECTIVE: Adenoid cystic carcinoma (AdCC) of the Bartholin's gland (AdCC-BG) is a very rare gynecologic vulvar malignancy. AdCC-BGs are slow-growing but locally aggressive and are associated with high recurrence rates. Here we sought to characterize the molecular underpinning of AdCC-BGs. METHODS: AdCC-BGs (n = 6) were subjected to a combination of RNA-sequencing, targeted DNA-sequencing, reverse-transcription PCR, fluorescence in situ hybridization (FISH) and MYB immunohistochemistry (IHC). Clinicopathologic variables, somatic mutations, copy number alterations and chimeric transcripts were assessed. RESULTS: All six AdCC-BGs were biphasic, composed of ductal and myoepithelial cells. Akin to salivary gland and breast AdCCs, three AdCC-BGs had the MYB::NFIB fusion gene with varying breakpoints, all of which were associated with MYB overexpression by IHC. Two AdCC-BGs were underpinned by MYBL1 fusion genes with different gene partners, including MYBL1::RAD51B and MYBL1::EWSR1 gene fusions, and showed MYB protein expression. Although the final AdCC-BG studied had MYB protein overexpression, no gene fusion was identified. AdCC-BGs harbored few additional somatic genetic alterations, and only few mutations in cancer-related genes were identified, including GNAQ, GNAS, KDM6A, AKT1 and BCL2, none of which were recurrent. Two AdCC-BGs, both with a MYB::NFIB fusion gene, developed metastatic disease. CONCLUSIONS: AdCC-BGs constitute a convergent phenotype, whereby activation of MYB or MYBL1 can be driven by the MYB::NFIB fusion gene or MYBL1 rearrangements. Our observations further support the notion that AdCCs, irrespective of organ site, constitute a genotypic-phenotypic correlation. Assessment of MYB or MYBL1 rearrangements may be used as an ancillary marker for the diagnosis of AdCC-BGs.

Pediatric-type diffuse low-grade gliomas.

The World Health Organization's 5th edition classification of Central Nervous System (CNS) tumors differentiates diffuse gliomas into adult and pediatric variants. Pediatric-type diffuse low-grade gliomas (pDLGGs) are distinct from adult gliomas in their molecular characteristics, biological behavior, clinical progression, and prognosis. Various molecular alterations identified in pDLGGs are crucial for treatment. There are four distinct entities of pDLGGs. All four of these tumor subtypes exhibit diffuse growth and share overlapping histopathological and imaging characteristics. Molecular analysis is essential for differentiating these lesions.

Characterization of MYBL1 Gene in Triple-Negative Breast Cancers and the Genes' Relationship to Alterations Identified at the Chromosome 8q Loci.

The MYBL1 gene is a strong transcriptional activator involved in events associated with cancer progression. Previous data show MYBL1 overexpressed in triple-negative breast cancer (TNBC). There are two parts to this study related to further characterizing the MYBL1 gene. We start by characterizing MYBL1 reference sequence variants and isoforms. The results of this study will help in future experiments in the event there is a need to characterize functional variants and isoforms of the gene. In part two, we identify and validate expression and gene-related alterations of MYBL1, VCIP1, MYC and BOP1 genes in TNBC cell lines and patient samples selected from the Breast Invasive Carcinoma TCGA 2015 dataset available at cBioPortal.org. The four genes are located at chromosomal regions 8q13.1 to 8q.24.3 loci, regions previously identified as demonstrating a high percentage of alterations in breast cancer. We identify alterations, including changes in expression, deletions, amplifications and fusions in MYBL1, VCPIP1, BOP1 and MYC genes in many of the same patients, suggesting the panel of genes is involved in coordinated activity in patients. We propose that MYBL1, VCPIP1, MYC and BOP1 collectively be considered as genes associated with the chromosome 8q loci that potentially play a role in TNBC pathogenesis.

The Landscape of MYB/MYBL1- and Peri-MYB/MYBL1-Associated Rearrangements in Adenoid Cystic Carcinoma.

Approximately 60% of adenoid cystic carcinoma (AdCC) cases are positive for MYB::NFIB or MYBL1::NFIB, whereas MYB/MYBL1 oncoprotein, a key driver of AdCC, is overexpressed in most cases. Juxtaposition of superenhancer regions in NFIB and other genes into the MYB/MYBL1 locus is an attractive oncogenic hypothesis for AdCC cases, either negative or positive for MYB/MYBL1::NFIB. However, evidence supporting this hypothesis is insufficient. We examined 160 salivary AdCC cases for rearrangements in MYB/MYBL1 loci and peri-MYB/MYBL1 areas (centromeric and telomeric areas of 10 Mb each) using formalin-fixed, paraffin-embedded tumor sections. For the detection of the rearrangements, we employed conventional fluorescence in situ hybridization split and fusion assays and a 5 Mb fluorescence in situ hybridization split assay. The latter is a novel assay that enabled us to detect any possible splits within a 5 Mb distance of a chromosome. We found MYB/MYBL1- and peri-MYB/MYBL1-associated rearrangements in 149/160 patients (93%). AdCC cases positive for rearrangements in MYB, MYBL1, the peri-MYB area, and the peri-MYBL1 area numbered 105 (66%), 20 (13%), 19 (12%), and 5 (3%), respectively. In 24 peri-MYB/MYBL1 rearrangement-positive cases, 14 (58%) were found to have a juxtaposition of the NFIB or RAD51B locus into the MYB/MYBL1 loci. On comparing with a tumor group positive for MYB::NFIB, a hallmark of AdCC, other genetically classified tumor groups had similar features of overexpression of the MYB transcript and MYB oncoprotein as detected by semiquantitative RT-qPCR and immunohistochemistry, respectively. In addition, clinicopathological and prognostic features were similar among these groups. Our study suggests that peri-MYB/MYBL1 rearrangements may be a frequent event in AdCC and may result in biological and clinicopathological consequences comparable to MYB/MYBL1 rearrangements. The landscape of MYB/MYBL1 and peri-MYB/MYBL1 rearrangements shown here strongly suggests that juxtaposition of superenhancers into MYB/MYBL1 or peri-MYB/MYBL1 loci is an alteration that acts as a key driver for AdCC oncogenesis and may unify MYB/MYBL1 rearrangement-positive and negative cases.

Molecular characterisation of tumours of the lacrimal apparatus.

AIMS: Malignant tumours of the lacrimal apparatus are rare and frequently show a poor prognosis, with no clear therapeutic standards. Characterisation of the genetic landscape of these rare tumours is sparse, and therefore therapeutics generally follow those of their common salivary gland counterparts. To further clarify the pathophysiology and discover potential therapeutic targets, we investigated the genetic landscape of eight tumours of the lacrimal apparatus. METHODS AND RESULTS: DNA and RNA sequencing were performed to identify genetic mutations and gene fusions. Immunohistochemistry, fluorescence in-situ hybridisation and reverse transcription-polymerase chain reaction followed by Sanger sequencing were performed to confirm the identified molecular alterations. Genetic alterations were detected in six tumours. Among five adenoid cystic carcinomas (ACC), four had confirmed alterations of MYB or MYBL1 genes, including a MYB::NFIB fusion, a MYBL1::NFIB fusion, a MYB amplification and a novel NFIB::THSD7B fusion. Mutations in genes encoding epigenetic modifiers, as well as NOTCH1, FGFR2 and ATM mutations, were also identified in ACCs. A carcinoma ex pleomorphic adenoma showed TP53 and CIC mutations and an amplification of ERBB2. A transitional cell carcinoma was associated with HPV16 infection. No genetic alteration was found for one adenocarcinoma, not otherwise specified. CONCLUSIONS: Our study highlights the variety of molecular alterations associated with lacrimal system tumours and emphasises the importance of molecular testing in these tumours, which can reveal potentially targetable mutations. Our results also reinforce the hypothesis of a common physiopathology of all ACCs, regardless of their primary location.

Adenoid cystic carcinoma in children and young adults: A clinicopathological study of 12 cases.

OBJECTIVE: To investigate the clinicopathological characteristics, immunoprofile, and molecular alterations of adenoid cystic carcinoma (ACC) in children and young adults. MATERIALS AND METHODS: Twelve cases of ACC were included. MYB, MYBL1, Ki-67, type IV Collagen, Laminin, and LAMB1 expression were detected by immunohistochemistry. MYB and MYBL1 rearrangements were detected by fluorescence in situ hybridization. RESULTS: Among 12 patients, four were female and eight were male. Seven cases (58.3%) located in major salivary glands and eight cases (66.7%) were classified as Grade I. Ten tumors (83.3%) had collagenous and hyalinized stroma. MYB was positive in 83.3% cases, and the average Ki-67 labeling index (LI) was 8.3%. LAMB1, type IV Collagen, and Laminin were positive in 91.7%, 66.7%, and 58.3% cases, respectively. Besides, three out of eight tumors had MYB rearrangement. Cases without MYB rearrangement were negative for MYBL1 expression and MYBL1 rearrangement. The average follow-up time was 91.8 months. Four patients had recurrent diseases. CONCLUSIONS: ACC in children and young adults was seen more frequently in males and major salivary glands. Most cases had ECM and hyaline stroma. Grade III tumors, higher Ki-67 LI, negative expression of type IV Collagen, and Laminin showed a tendency of higher recurrence rate.

Evaluation of MYBL1 as the master regulator for pachytene spermatocyte genes dysregulated in interspecific hybrid dzo.

Misregulation of spermatogenesis transcription factors (TF) in hybrids can lead to misexpression, which is a mechanism for hybrid male sterility (HMS). We used dzo (male offspring of Bos taurus ♂ × Bos grunniens ♀) in bovines to investigate the relationship of the key TF with HMS via RNA sequencing and assay for transposase-accessible chromatin with high-throughput sequencing analyses. RNA sequencing showed that the widespread misexpression in dzo was associated with spermatogenesis-related genes and somatic or progenitor genes. The transition from leptotene or zygotene spermatocytes to pachytene spermatocytes may be the key stage for meiosis arrest in dzo. The analysis of TF-binding motif enrichment revealed that the male meiosis-specific master TF MYB proto-oncogene like 1 (MYBL1, known as A-MYB) motif was enriched on the promoters of downregulated pachytene spermatocyte genes in dzo. Assay for transposase-accessible chromatin with high-throughput sequencing revealed that TF-binding sites for MYBL1, nuclear transcription factor Y, and regulatory factor X were enriched in the low-chromatin accessibility region of dzo. The target genes of the MYBL1-binding motif were associated with meiosis-specific genes and significantly downregulated in dzo testis. The transcription factor MYBL1 may be the candidate master regulator for pachytene spermatocyte genes dysregulated in interspecific HMS dzo. This study reported that a few upstream TF regulation changes might exert a cascading effect downstream in a regulatory network as a mechanism for HMS.

miR-145-3p Inhibits MuSCs Proliferation and Mitochondria Mass via Targeting MYBL1 in Jianzhou Big-Eared Goats.

Muscle growth and injury-induced regeneration are controlled by skeletal muscle satellite cells (MuSCs) through myogenesis in postnatal animals. Meanwhile, myogenesis is accompanied by mitochondrial function and enzyme activity. Nevertheless, the underlying molecular mechanisms involving non-coding RNAs including circular RNAs (circRNAs) and microRNAs (miRNAs) remain largely unsolved. Here, we explored the myogenic roles of miR-145-3p and MYBL1 on muscle development and mitochondrial mass. We noticed that overexpression of miR-145-3p inhibited MuSCs proliferation and reduced the number of viable cells. Meanwhile, deficiency of miR-145-3p caused by LNAantimiR-145-3p or an inhibitor retarded the differentiation of MuSCs. miR-145-3p altered the mitochondrial mass in MuSCs. Moreover, miR-145-3p targeted and negatively regulated the expression of CDR1as and MYBL1. The knockdown of the MYBL1 using ASO-2'MOE modification simulated the inhibitory function of miR-145-3p on cell proliferation. Additionally, MYBL1 mediated the regulation of miR-145-3p on Vexin, VCPIP1, COX1, COX2, and Pax7. These imply that CDR1as/miR-145-3p/MYBL1/COX1, COX2, VCPIP1/Vexin expression at least partly results in a reduction in mitochondrial mass and MuSCs proliferation. These novel findings confirm the importance of mitochondrial mass during myogenesis and the boosting of muscle/meat development in mammals.

Paediatric-type diffuse low-grade gliomas: a clinically and biologically distinct group of tumours with a favourable outcome.

The WHO 2021 classification of central nervous system cancers distinguishes diffuse gliomas that arise in adults (referred to as the "adult type") and those that arise in children (defined as "paediatric") based on clinical and molecular characteristics."). However, paediatric-type gliomas may occasionally be present in younger adults and occasionally adult-type gliomas may occur in children. Diffuse low-grade paediatric glioma includes diffuse astrocytoma altered by MYB or MYBL1, low-grade polymorphic juvenile neuroepithelial tumour, angiocentric glioma, and diffuse low-grade glioma with an altered MAPK pathway. Here, we examine these newly recognised entities according to WHO diagnostic criteria and propose an integrated diagnostic approach that can be used to separate these clinically and biologically distinct tumor groups.

[Low grade glioma with MYBL1 alteration: Case report of an uncommon pediatric neoplasm]. / Gliome de bas grade avec altération de MYBL1 : observation d'une nouvelle entité tumorale pédiatrique.

Diffuse gliomas with MYB or MYBL1 alterations are rare tumours mostly affecting children or young adults with long-term epilepsy. This category of glioma includes two morphological subtypes. The angiocentric subtype is characterized by an angiocentric pattern of growth and a frequent MYB:QKI fusion. The isomorphic subtype corresponds to a highly differentiated astrocytic glioma with low cellularity, low proliferation and no specific microscopic features. The diagnosis is based on the imaging, demonstrating a supratentorial tumor, associated with the confirmation of a MYB or MYBL1 rearrangement. Here, we report the case of a 7-year-old child who presented a right frontal brain lesion corresponding to an isomorphic diffuse glioma with MYBL1 alteration.

Isomorphic diffuse glioma is a morphologically and molecularly distinct tumour entity with recurrent gene fusions of MYBL1 or MYB and a benign disease course.

The "isomorphic subtype of diffuse astrocytoma" was identified histologically in 2004 as a supratentorial, highly differentiated glioma with low cellularity, low proliferation and focal diffuse brain infiltration. Patients typically had seizures since childhood and all were operated on as adults. To define the position of these lesions among brain tumours, we histologically, molecularly and clinically analysed 26 histologically prototypical isomorphic diffuse gliomas. Immunohistochemically, they were GFAP-positive, MAP2-, OLIG2- and CD34-negative, nuclear ATRX-expression was retained and proliferation was low. All 24 cases sequenced were IDH-wildtype. In cluster analyses of DNA methylation data, isomorphic diffuse gliomas formed a group clearly distinct from other glial/glio-neuronal brain tumours and normal hemispheric tissue, most closely related to paediatric MYB/MYBL1-altered diffuse astrocytomas and angiocentric gliomas. Half of the isomorphic diffuse gliomas had copy number alterations of MYBL1 or MYB (13/25, 52%). Gene fusions of MYBL1 or MYB with various gene partners were identified in 11/22 (50%) and were associated with an increased RNA-expression of the respective MYB-family gene. Integrating copy number alterations and available RNA sequencing data, 20/26 (77%) of isomorphic diffuse gliomas demonstrated MYBL1 (54%) or MYB (23%) alterations. Clinically, 89% of patients were seizure-free after surgery and all had a good outcome. In summary, we here define a distinct benign tumour class belonging to the family of MYB/MYBL1-altered gliomas. Isomorphic diffuse glioma occurs both in children and adults, has a concise morphology, frequent MYBL1 and MYB alterations and a specific DNA methylation profile. As an exclusively histological diagnosis may be very challenging and as paediatric MYB/MYBL1-altered diffuse astrocytomas may have the same gene fusions, we consider DNA methylation profiling very helpful for their identification.

MYBL1 rearrangements and MYB amplification in breast adenoid cystic carcinomas lacking the MYB-NFIB fusion gene.

Breast adenoid cystic carcinoma (AdCC), a rare type of triple-negative breast cancer, has been shown to be driven by MYB pathway activation, most often underpinned by the MYB-NFIB fusion gene. Alternative genetic mechanisms, such as MYBL1 rearrangements, have been reported in MYB-NFIB-negative salivary gland AdCCs. Here we report on the molecular characterization by massively parallel sequencing of four breast AdCCs lacking the MYB-NFIB fusion gene. In two cases, we identified MYBL1 rearrangements (MYBL1-ACTN1 and MYBL1-NFIB), which were associated with MYBL1 overexpression. A third AdCC harboured a high-level MYB amplification, which resulted in MYB overexpression at the mRNA and protein levels. RNA-sequencing and whole-genome sequencing revealed no definite alternative driver in the fourth AdCC studied, despite high levels of MYB expression and the activation of pathways similar to those activated in MYB-NFIB-positive AdCCs. In this case, a deletion encompassing the last intron and part of exon 15 of MYB, including the binding site of ERG-1, a transcription factor that may downregulate MYB, and the exon 15 splice site, was detected. In conclusion, we demonstrate that MYBL1 rearrangements and MYB amplification probably constitute alternative genetic drivers of breast AdCCs, functioning through MYBL1 or MYB overexpression. These observations emphasize that breast AdCCs probably constitute a convergent phenotype, whereby activation of MYB and MYBL1 and their downstream targets can be driven by the MYB-NFIB fusion gene, MYBL1 rearrangements, MYB amplification, or other yet to be identified mechanisms. Copyright © 2017 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

MYB, MYBL1, MYBL2 and NFIB gene alterations and MYC overexpression in salivary gland adenoid cystic carcinoma.

AIMS: Adenoid cystic carcinoma (AdCC) is one of the most common salivary gland malignancies and the long-term prognosis is poor. In this study, we examined alterations of AdCC-associated genes, MYB, MYBL1, MYBL2 and NFIB, and their target molecules, including MYC. The results were correlated to clinicopathological profile of the patients. METHODS AND RESULTS: Using paraffin tumour sections from 33 cases of salivary gland AdCC, we performed a detailed fluorescence in-situ hybridization (FISH) analysis for gene splits and fusions of MYB, MYBL1, MYBL2 and NFIB. We found that 29 of 33 (88%) AdCC cases showed gene splits in either MYB, MYBL1 or NFIB. None of the cases showed an MYBL2 gene alteration. AdCCs were divided genetically into six gene groups, MYB-NFIB (n = 16), MYB-X (n = 4), MYBL1-NFIB (n = 2), MYBL1-X (n = 1), NFIB-X (n = 6) and gene-split-negative (n = 4). AdCC patients showing the MYB or MYBL1 gene splits were associated with microscopically positive surgical margins (P = 0.0148) and overexpression of MYC (P = 0.0164). MYC expression was detected in both ductal and myoepithelial tumour cells, and MYC overexpression was associated with shorter disease-free survival of the patients (P = 0.0268). CONCLUSIONS: The present study suggests that (1) nearly 90% of AdCCs may have gene alterations of either MYB, MYBL1 or NFIB, suggesting the diagnostic utility of the FISH assay, (2) MYB or MYBL1 gene splits may be associated with local aggressiveness of the tumours and overexpression of MYC, which is one of the oncogenic MYB/MYBL1 targets and (3) MYC overexpression may be a risk factor for disease-free survival in AdCC.

Human papillomavirus-related carcinoma with adenoid cystic-like features of the sinonasal tract: clinical and morphological characterization of six new cases.

AIMS: Human papillomavirus (HPV) is known as causative for squamous cell carcinoma (SCC) of the oropharynx, but is also found not infrequently in carcinomas of the sinonasal tract. Recently, a subset of these carcinomas was recognized to harbour HPV33 and have a significant morphological overlap with adenoid cystic carcinoma (ACC), a rare and aggressive carcinoma originating in the minor salivary glands. Termed 'HPV-related carcinoma with ACC-like features', only nine cases have been reported. To clarify the occurrence of these tumours we screened a large material for the presence of HPV-related ACC-like carcinoma. The identified tumours were characterized immunohistochemically and with fluorescence in-situ hybridization, and clinicopathological information for all cases is presented. METHODS AND RESULTS: Forty-seven candidate cases were screened for presence of HPV. Six cases were identified and genotyped as HPV types 33, 35, and 56. All six cases had areas of dysplastic mucosal lining and showed remarkable heterogeneous morphologies. MYB, MYBL1, and NFIB genes were intact and, interestingly, staining for MYB protein was largely negative in contrast to what was found in ACC. One patient experienced a local recurrence 11 years after initial treatment and the remaining five patients were alive without evidence of disease. CONCLUSION: We report six new cases of HPV-related ACC-like carcinoma and found that, although in a small material, the prognosis for these patients seems more favourable than for ACC. For the distinction between ACC and HPV-related ACC-like carcinoma, p16, MYB immunohistochemistry or investigation of MYB, MYBL1 and NFIB gene status are valuable.

Targeted genomic analysis of Müllerian adenosarcoma.

Müllerian adenosarcoma (MA) is a rare mixed mesenchymal tumour of the female genital tract, composed of malignant stroma and benign-appearing epithelium. Sarcomatous overgrowth (SO) is the only established histological variable associated with higher stage and shorter survival. Specific molecular or immunohistochemistry (IHC) tools for the diagnosis of MA are lacking. Our goal was to study genomic mutations and copy number variations (CNVs) in MA to understand better its pathobiology, and develop specific diagnostic and prognostic tools. DNA was extracted from 20 samples of MA from 18 subjects (12 without SO and 6 with SO), including two in which areas of both typical MA histology and SO were independently tested. Samples were analysed using a targeted next-generation sequencing assay interrogating exonic sequences of 275 cancer genes for mutations and CNVs as well as 91 introns across 30 genes for cancer-associated rearrangements. The mean number of mutations in MA with SO (mean 9.7; range 3-14) did not differ significantly from that in MA without SO (mean 9.6; range 5-16). MA with SO had significantly higher mean numbers of gene-level CNVs (24.6) compared to MA without SO (5; p = 0.0002). The most frequent amplification involved MDM2 and CDK4 (5/18; 28%), accompanied by focal CDK4 and MDM2 and diffuse HMGA2 expression using immunohistochemistry. MYBL1 amplification was seen in 4/18 (22%), predominantly in SO. Alterations in PIK3CA/AKT/PTEN pathway members were seen in 13/18 (72%). Notably, TP53 mutations were uncommon, present in only two cases with SO. Three out of 18 (17%) had mutations in ATRX, all associated with SO. No chromosomal rearrangements were identified. We have identified a number of recurrent genomic alterations in MA, including some associated with SO. Although further investigation of these findings is needed, confirmation of one or more may lead to new mechanistic insights and novel markers for this often difficult-to-diagnose tumour.

Chicken gga-miR-181a targets MYBL1 and shows an inhibitory effect on proliferation of Marek's disease virus-transformed lymphoid cell line.

Marek's disease (MD), caused by Marek's disease virus (MDV), is a lymphoproliferative neoplastic disease of chickens and is characterized by MD lymphoma in multiple visceral organs of chicken. It causes great damage to poultry health. Recently, miRNA has been reported to be involved in Marek's disease lymphomagenesis. Our previous study showed that gga-miR-181a was downregulated in MDV-induced lymphoma, and its target gene, v-myb myeloblastosis viral oncogene homolog-like 1 (MYBL1), was predicted. In this study, the interaction between gga-miR-181a and MYBL1 was further verified by detecting protein expression levels of MYBL1 after transfecting miR-181a mimic into MD lymphoma cell line, MSB1. The result showed that protein level of MYBL1 was lower in gga-miR-181a mimic transfecting group than that in the negative control group at 96 h post transfection, which indicated that MYBL1 was a target gene of gga-miR-181a. Additionally, we found that the expression of MYBL1 was higher in MDV-infected samples than that in non-infected controls, which agreed with the proposition that miRNA showed a negatively correlated expression pattern with its target gene. We observed the inhibitory effect of gga-miR-181a on MSB1 cell proliferation. Collectively, the aberrant expression of gga-miR-181a and MYBL1 in MD lymphoma suggested that they might be involved in MD tumor transformation and played important roles.

Astrocytoma with high-grade features and MYBL1-MMP16 fusion.

Background: Gliomas represent the most common primary intraparenchymal brain tumors in adult and pediatric patients. Neuropathological work-up of these gliomas typically entails the determination of isocitrate dehydrogenase (IDH) mutational status, presence or absence of 1p/19q co-deletion, and O6 methylguanine-DNA methyl-transferase (MGMT) promoter methylation status. Case Description: We present here an unusual case of a posterior fossa tumor in a 51-year-old female, which was initially diagnosed as astrocytoma with some high-grade features that recurred, displaying even more aggressive features such as infiltration and increased proliferative activity. Both the initially resected and recurrent tumor revealed MYBL1-MMP16 fusion, which is much more commonly found in pediatric low-grade gliomas and, to our knowledge has not been described in the context of an adult glioma. Conclusion: The significance of MYBL1-MMP16 fusion in adult gliomas in relation to survival and likelihood of recurrence is, therefore, unknown and requires more extensive research.

Comprehensive analysis of MYB/MYBL1-altered pediatric-type diffuse low-grade glioma.

BACKGROUND: Pediatric-type diffuse low-grade gliomas (pLGG) harboring recurrent genetic alterations involving MYB or MYBL1 are closely related tumors. Detailed treatment and outcome data of large cohorts are still limited. This study aimed to comprehensively evaluate pLGG with these alterations to define optimal therapeutic strategies. METHODS: We retrospectively reviewed details of pLGG with MYB or MYBL1 alterations from patients treated or referred for pathologic review at St. Jude Children's Research Hospital. Tumor specimens were centrally reviewed, and clinical data were collated. RESULTS: Thirty-three patients (18 male; median age, 5 years) were identified. Two tumors had MYBL1 alterations; 31 had MYB alterations, MYB::QKI fusion being the most common (n = 10, 30%). Most tumors were in the cerebral hemispheres (n = 22, 67%). Two patients (6%) had metastasis at diagnosis. The median follow-up was 6.1 years. The 5-year event-free survival (EFS) rate was 81.3% ±â€…8.3%; the 5-year overall survival (OS) rate was 96.4% ±â€…4.1%. Patients receiving a near-total or gross-total resection had a 5-year EFS of 100%; those receiving a biopsy or subtotal resection had a 5-year EFS rate of 56.6% ±â€…15.2% (P < .01). No difference in EFS was observed based on location, histology, or molecular alterations. However, the tumors that progressed or metastasized may have distinct methylation profiles with evidence of activation of the MAPK and PI3K/AKT/mTOR pathways. CONCLUSIONS: pLGG with MYB/MYBL1 alterations have good outcomes. Our findings suggest that surgical resectability is a crucial determinant of EFS. Further characterization is required to identify optimal treatment strategies for progressive tumors.

Pediatric-type diffuse low-grade glioma with MYB/MYBL1 alteration: report of 2 cases.

2016 World Health Organization (WHO) Classification of Tumors of the Central Nervous System (CNS) has shown how molecular features can impact the classification of brain tumors. The continued combination of molecular features with histopathology has led to distinguish tumors with similar histopathologic features but distinct clinical prognosis. The 2021 revised 5. edition of the WHO classification further includes molecular features for CNS tumor categorization including MYB/MYBL1 altered diffuse astrocytoma which is a newly recognized type of low-grade pediatric-type brain tumor. We discuss imaging features of two pediatric-type low-grade gliomas with MYB/MYBL1-mutation that encountered at our institution.

MYB/MYBL1::QKI fusion-positive diffuse glioma.

The MYB/MYBL1::QKI fusion induces the protooncogene, MYB, and deletes the tumor suppressor gene, QKI. MYB/MYBL1::QKI rearrangement was previously reported only in angiocentric glioma (AG) and diffuse low-grade glioma. This report compares 2 tumors containing the MYB/MYBL1::QKI fusion: a diffuse pediatric-type high-grade glioma (DPedHGG) in an 11-year-old boy and an AG in a 46-year-old woman. We used immunohistochemistry, next-generation sequencing, and methylation profiling to characterize each tumor and compare our findings to the literature on AG and tumors with the MYB/MYBL1::QKI rearrangement. Both tumors were astrocytic with angiocentric patterns. The MYB::QKI fusion-positive DPedHGG, which recurred once, was accompanied by TP53 mutation and amplification of CDK6 and KRAS, suggesting malignant transformation secondary to additional genetic aberrations. The second case was the adult AG with MYBL1::QKI fusion, which mimicked ependymoma based on histopathology and its dot- and ring-like epithelial membrane antigen positivity. Combined with a literature review, our results suggest that MYB/MYBL1 alterations are not limited to low-grade gliomas, including AG. AG is most common in the cerebra of children and adolescents but exceptional cases occur in adults and the acquisition of additional genetic mutations may contribute to high-grade glioma. These cases further demonstrate that molecular characteristics, morphologic features, and clinical context are essential for diagnosis.