Pleomorphic xanthoastrocytoma (PXA) is a rare localized glioma characterized by frequent BRAF V600E mutation and CDKN2A/B deletion. We explored the association of copy-number variants (CNVs) with BRAF mutations, tumor grade, and patient survival in a cohort of 41 PXA patients using OncoScan chromosomal microarray. Primary resection specimens were available in 38 cases, including 24 PXA and 14 anaplastic PXA (A-PXA), 23 BRAF V600E mutant tumors (61%). CNVs were identified in all cases and most frequently involved chromosome 9 with homozygous CDKN2A/B deletion (n = 33, 87%), a higher proportion than previously detected by comparative genomic hybridization (50%-60%) (37). CDKN2A/B deletion was present in similar proportion of PXA (83%), A-PXA (93%), BRAF V600E (87%), and wild-type (87%) tumors. Whole chromosome gains/losses were frequent, including gains +7 (n = 15), +2 (n = 11), +5 (n = 10), +21 (n = 10), +20 (n = 9), +12 (n = 8), +15 (n = 8), and losses -22 (n = 11), -14 (n = 7), -13 (n = 5). Losses and copy-neutral loss of heterozygosity were significantly more common in A-PXA, involving chromosomes 22 (P = 0.009) and 14 (P = 0.03). Amplification of 8p and 12q was identified in a single tumor. Histologic grade was a robust predictor of overall survival (P = 0.003), while other copy-number changes, including CDKN2A/B deletion, did not show significant association with survival. Distinct histologic patterns of anaplasia included increased mitotic activity in an otherwise classic PXA or associated with small cell, fibrillary, or epithelioid morphology, with loss of SMARCB1 expression in one case. In 10 cases, matched specimens were compared, including A-PXA with areas of distinct low- and high-grade morphology (n = 2), matched primary/tumor recurrence (n = 7), or both (n = 1). Copy-number changes on recurrence/anaplastic transformation were complex and highly variable, from nearly identical profiles to numerous copy-number changes. Overall, we confirm CDKN2A/B deletion as key a feature of PXA not associated with tumor grade or BRAF mutation, but central to the underlying genetics of PXA.
Low-grade gliomas represent the most frequent primary brain tumors in children, and are also an important category of brain neoplasms in young adults. They are characterized by slow growth, but often associated with increased morbidity, as well as mortality in the subset that develop histologic progression. Pathologically they correspond to WHO grade I or II and include pilocytic astrocytoma (PA), pilomyxoid astrocytoma variant, angiocentric glioma, diffuse astrocytoma, oligodendroglioma, oligoastrocytoma, and pleomorphic xanthoastrocytoma (PXA). Although all low-grade glioma subtypes may develop in children and adults, and be histologically indistinguishable in these two populations, there are important clinical and molecular differences. As a rule, low-grade gliomas in adults have a greater tendency for histologic progression and more aggressive clinical behavior than those in children. With respect to genetic alterations, activating BRAF alterations and increased MAPK pathway signaling are near universal features of the circumscribed low-grade glioma group (e.g., PA and PXA). Whole exome/genome sequencing efforts and high resolution copy number platforms have also provided important biologic insights in these tumors, with adult low-grade diffuse gliomas containing frequent ATRX, TP53 mutations (astrocytomas), as well as 1p19q co-deletions, CIC, FUBP1 and TERT promoter mutations (oligodendrogliomas). Conversely, alterations in FGFR1, MYB, and MYBL1 are frequent events in pediatric low-grade diffuse gliomas. In this review we summarize our current knowledge of the diagnostic and molecular pathology of these tumors, and explore possible avenues for targeted therapeutics.
<div>Abstract<p>Purpose: Treatment of wingless (WNT)-activated medulloblastoma (WNT+MB) with surgery, irradiation (XRT) and chemotherapy results in excellent outcomes. We studied the efficacy of therapy de-intensification by omitting XRT entirely in children with WNT+MB. Patients and Methods: Tumors were molecularly screened to confirm the diagnosis of WNT+MB. Eligible children were treated within 31 days following surgery with nine cycles of adjuvant chemotherapy per ACNS0331. No XRT was planned. The primary endpoint was the occurrence of relapse, progression, or death in the absence of XRT within the first two years after study enrollment. Four events in the first 10 evaluable patients would result in early study closure. Results: Fourteen children were prescreened and nine met the protocol definition of WNT+MB. Six of the nine eligible patients consented to protocol therapy and five completed planned protocol therapy. The first two children enrolled relapsed shortly after therapy completion with local and leptomeningeal recurrences. The study was closed early due to safety concerns. Both children are surviving after XRT and additional chemotherapy. A third child relapsed at completion of therapy but died of progressive disease 35 months from diagnosis. Two children finished treatment but immediately received post-treatment XRT to guard against early relapse. The final child’s treatment was aborted in favor of a high-dose therapy/stem cell rescue approach. While OS at 5 years is 83%, no child received only planned protocol therapy with all receiving eventual XRT and/or alternative therapy. Conclusions: Radiation therapy is required to effectively treat children with WNT-altered medulloblastoma.</p></div>
<div>Abstract<p>The <i>Sleeping Beauty</i> (SB) transposon system has been used as a somatic mutagen to identify candidate cancer genes. In previous studies, efficient leukemia/lymphoma formation on an otherwise wild-type genetic background occurred in mice undergoing whole-body mobilization of transposons, but was accompanied by high levels of embryonic lethality. To explore the utility of SB for large-scale cancer gene discovery projects, we have generated mice that carry combinations of different transposon and transposase transgenes. We have identified a transposon/transposase combination that promotes highly penetrant leukemia/lymphoma formation on an otherwise wild-type genetic background, yet does not cause embryonic lethality. Infiltrating gliomas also occurred at lower penetrance in these mice. SB-induced or accelerated tumors do not harbor large numbers of chromosomal amplifications or deletions, indicating that transposon mobilization likely promotes tumor formation by insertional mutagenesis of cancer genes, and not by promoting wide-scale genomic instability. Cloning of transposon insertions from lymphomas/leukemias identified common insertion sites at known and candidate novel cancer genes. These data indicate that a high mutagenesis rate can be achieved using SB without high levels of embryonic lethality or genomic instability. Furthermore, the SB system could be used to identify new genes involved in lymphomagenesis/leukemogenesis. [Cancer Res 2009;69(21):8429–37]</p></div>
Epstein-Barr virus (EBV)-associated smooth muscle tumors (SMTs) have recently been associated with primary and secondary immunodeficiencies. They are broadly divided into 3 subgroups: HIV-related, posttransplant, and congenital immunodeficiency. Subsequent to organ transplantation and acquired immunosuppression, a few cases of EBV-associated SMTs have been described in the liver, respiratory tract, and gastrointestinal system. To the authors' knowledge, intracranial involvement after peripheral blood stem cell transplantation has never been reported previously. The authors describe the case of a 65-year-old woman who presented with recent-onset painful ophthalmoplegia. She had a prior history of acute myelogenous leukemia requiring allogenic peripheral blood stem cell transplantation 2 years earlier, but she was in a remission phase. Imaging revealed a T1/T2 isointense, homogeneously enhancing lesion of the left cavernous sinus. A presumptive diagnosis of Tolosa-Hunt syndrome was made, and she was treated with steroids; however, her symptoms progressed quickly and repeat imaging revealed that the lesion was growing. To rule out leukemic deposits, a minimally invasive lateral orbitotomy extradural transcavernous approach was performed for biopsy sampling and debulking of the lesion. The biopsied tumor tissue was found to be infiltrative, grayish, firm, and moderately vascular. The final pathology results indicated an EBV-associated SMT of the cavernous sinus. Subsequently, the patient's steroid treatment was stopped and she had obtained partial symptomatic relief at her last follow-up visit, 3 months after surgery. EBV-associated SMT should be included in the differential diagnosis for intracranial and dural-based central nervous system lesions, especially in immunocompromised patients. Paradoxical response to steroids with worsening of symptoms is a hallmark of EBV-associated SMTs.
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