Subclonal Cancer Driver Mutations Are Prevalent in the Unresected Peritumoral Edema of Adult Diffuse Gliomas.

Adult diffuse gliomas commonly recur regardless of therapy. As recurrence typically arises from the peritumoral edema adjacent to the resected bulk tumor, the profiling of somatic mutations from infiltrative malignant cells within this critical, unresected region could provide important insights into residual disease. A key obstacle has been the inability to distinguish between next-generation sequencing (NGS) noise and the true but weak signal from tumor cells hidden among the noncancerous brain tissue of the peritumoral edema. Here, we developed and validated True2 sequencing to reduce NGS-associated errors to <1 false positive/100 kb panel positions while detecting 97.6% of somatic mutations with an allele frequency ≥0.1%. True2 was then used to study the tumor and peritumoral edema of 22 adult diffuse gliomas including glioblastoma, astrocytoma, oligodendroglioma, and NF1-related low-grade neuroglioma. The tumor and peritumoral edema displayed a similar mutation burden, indicating that surgery debulks these cancers physically but not molecularly. Moreover, variants in the peritumoral edema included unique cancer driver mutations absent in the bulk tumor. Finally, analysis of multiple samples from each patient revealed multiple subclones with unique mutations in the same gene in 17 of 22 patients, supporting the occurrence of convergent evolution in response to patient-specific selective pressures in the tumor microenvironment that may form the molecular foundation of recurrent disease. Collectively, True2 enables the detection of ultralow frequency mutations during molecular analyses of adult diffuse gliomas, which is necessary to understand cancer evolution, recurrence, and individual response to therapy. SIGNIFICANCE: True2 is a next-generation sequencing workflow that facilitates unbiased discovery of somatic mutations across the full range of variant allele frequencies, which could help identify residual disease vulnerabilities for targeted adjuvant therapies.

Targeted Next-Generation Sequencing Reveals Divergent Clonal Evolution in Components of Composite Pleomorphic Xanthoastrocytoma-Ganglioglioma.

Composite pleomorphic xanthoastrocytoma-ganglioglioma (PXA-GG) is an extremely rare central nervous system neoplasm with 2 distinct but intermingled components. Whether this tumor represents a "collision tumor" of separate neoplasms or a monoclonal neoplasm with divergent evolution is poorly understood. Clinicopathologic studies and capture-based next generation sequencing were performed on extracted DNA from all available PXA-GG at 2 medical centers. Five PXA-GG were diagnosed in 1 male and 4 female patients ranging from 13 to 25 years in age. Four arose within the cerebral hemispheres; 1 presented in the cerebellar vermis. DNA was sufficient for analysis in 4 PXA components and 3 GG components. Four paired PXA and GG components harbored BRAF p.V600E hotspot mutations. The 4 sequenced PXA components demonstrated CDKN2A homozygous deletion by sequencing with loss of p16 (protein product of CDKN2A) expression by immunohistochemistry, which was intact in all assessed GG components. The PXA components also demonstrated more frequent copy number alterations relative to paired GG components. In one PXA-GG, shared chromosomal copy number alterations were identified in both components. Our findings support divergent evolution of the PXA and GG components from a common BRAF p.V600E-mutant precursor lesion, with additional acquisition of CDKN2A homozygous deletion in the PXA component as is typically seen in conventional PXA.

Biopsy-proven PML in an HIV-negative patient with discoid lupus: Failure to detect JC virus in CSF.

We present a case of a 58-year-old man with a history of severe discoid lupus erythematosus and acute encephalopathy and incoordination. Antinuclear antibody testing was weakly positive but all other laboratory tests for systemic lupus erythematosus were negative and serum quantitative immunoglobulins and lymphocytes were normal. MRI brain showed T2/FLAIR hyperintensities within the bilateral parietal and temporal lobes with involvement of subcortical U fibers. CSF PCR was negative for varicella-zoster virus, herpes simplex, JCV and BK virus. However, JCV antibody index was elevated (3.88; reference: < 0.2). Right parietal brain biopsy was consistent with JCV infection and diagnostic of progressive multifocal leukoencephalopathy (PML). To the best of our knowledge, this is the first reported case of PML in a patient with discoid lupus without other traditional risk factors for the disease and highlights the need for clinical vigilance in this patient population.

Central nervous system involvement by myeloid sarcoma: a report of 12 cases and review of the literature.

Myeloid sarcoma (MS) is an extramedullary malignancy of myeloid origin. It can occur in any organ. Common sites are skin, bone, lymph nodes, and soft tissue. Central nervous system (CNS) involvement is very uncommon. We report 12 new pathology-confirmed cases of CNS MS with literature review. Median age was 42.5 years (range: 0 - 84 years). Bone marrow involvement by hematologic neoplasia was co-incidental (n = 8) or occurred 8 - 51 months prior to CNS MS (n = 3). Abnormal radiological findings detected in all patients, included hemorrhagic (n = 5) or enhancing (n = 2) lesions, with multiple ring-enhancing dura-based masses in 1 patient. Seven tumors had abnormal cytogenetics including: t(11; 19) (q23; p13.3), +8, inv (16), t(9; 22), t(8; 21), del(5q), and +21. One had a complex karyotype and 2 were cytogenetically normal. One MS had the JAK2V617F mutation. Treatment modalities included surgery for decompression (n = 2), radiotherapy (n = 2), chemotherapy (n = 6), and stem cell transplant (n = 2). Nine patients died days to 12 months post CNS MS diagnosis (median = 4 months). Two patients were alive without evidence of disease at 16 and 50 months following MS diagnosis and one was lost to follow-up. The clinical and imaging features for CMS MS overlap with those of intracranial hemorrhage and primary CNS tumors. It is therefore important to maintain a high index of suspicion and perform a biopsy whenever clinically appropriate. A meticulous workup is necessary to avoid misdiagnosis of other hematopoietic or nonhematopoietic neoplasms. Since CNS MS is potentially curable, timely recognition is paramount.

Mosaic amplification of multiple receptor tyrosine kinase genes in glioblastoma.

Tumor heterogeneity has been implicated in tumor growth and progression as well as resistance to therapy. We present an example of genetic heterogeneity in human malignant brain tumors in which multiple closely related driver genes are amplified and activated simultaneously in adjacent intermingled cells. We have observed up to three different receptor tyrosine kinases (EGFR, MET, PDGFRA) amplified in single tumors in different cells in a mutually exclusive fashion. Each subpopulation was actively dividing, and the genetic changes resulted in protein production, and coexisting subpopulations shared common early genetic mutations indicating their derivation from a single precursor cell. The stable coexistence of different clones within the same tumor will have important clinical implications for tumor resistance to targeted therapies.

Inhibition of Hedgehog signaling enhances delivery of chemotherapy in a mouse model of pancreatic cancer.

Pancreatic ductal adenocarcinoma (PDA) is among the most lethal human cancers in part because it is insensitive to many chemotherapeutic drugs. Studying a mouse model of PDA that is refractory to the clinically used drug gemcitabine, we found that the tumors in this model were poorly perfused and poorly vascularized, properties that are shared with human PDA. We tested whether the delivery and efficacy of gemcitabine in the mice could be improved by coadministration of IPI-926, a drug that depletes tumor-associated stromal tissue by inhibition of the Hedgehog cellular signaling pathway. The combination therapy produced a transient increase in intratumoral vascular density and intratumoral concentration of gemcitabine, leading to transient stabilization of disease. Thus, inefficient drug delivery may be an important contributor to chemoresistance in pancreatic cancer.