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Mayo Clinic Laboratories > Oncology > Neuro-oncology > Molecular and cytogenetic testing

Molecular and cytogenetic testing

Supporting precision oncology and patient care with comprehensive multiomic genetic sequencing, cytogenetic testing, and epigenetic testing

Rapid technological advancements and medical discoveries related to molecular tumor testing have redefined diagnosis and treatment for patients with central nervous system, or CNS, tumors. Accurately diagnosing CNS tumors can be challenging, however, due to overlapping histologic features, limited tissue samples, and evolving tumor classifications.

To address these challenges, we offer a full menu of advanced genetic, cytogenetic, and epigenetic testing to complement standard morphological and immunohistochemical assessment. Including MayoComplete next-generation sequencing (NGS) of both DNA and RNA, chromosomal microarray, and genome-wide methylation array analysis, our molecular testing serves as a powerful tool to assist in the diagnosis and selection of targeted therapies for CNS tumors.

Since 2021, molecular biomarkers — including mutations, fusions, copy number abnormalities, and methylation profile — have been integrated in the World Health Organization Classification of CNS Tumors. Additionally, targeted therapies have been clinically approved for patients with CNS tumors whose tumors have specific molecular biomarkers. Our neuro-oncology molecular testing portfolio includes the evaluation of all molecular biomarkers defined by the WHO classification.

In a Mayo Clinic study of adult patients with a glioma, comprehensive genetic sequencing and cytogenetic analysis resulted in a significant positive impact on patients.1 Of 379 patients seen:

Molecular and cytogenetic test menu

Next-generation DNA and RNA sequencing

Our neuro-oncology NGS panel is part of our suite of MayoComplete panels. This robust test includes most abnormalities described by the World Health Organization 2021 Classifications.2 It includes a DNA subpanel that assesses alterations in 89 genes and a comprehensive whole transcriptome RNA subpanel that assesses fusions and rearrangements in 1,445 genes, including known abnormal transcript variants in the MET and EGFR genes.

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Mayo Complete next-generation RNA sequencing

Our unique-to-the-market, targeted RNA panel uses NGS to evaluate 1,445 genes within the RNA transcriptome for somatic gene fusions. Used as a complement to DNA-only sequencing, RNA sequencing efficiently and accurately detects genetic fusions, including identification of new or unknown fusion partners and fusions with novel breakpoints. By including evaluation of transcriptome areas typically underrepresented in existing testing, this assay offers an enhanced ability to detect challenging fusions.

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Chromosomal microarray

Chromosomal microarray provides high-resolution assessment of copy number variations across the genome. According to published guidelines, when these abnormalities are found in diffuse astrocytic gliomas, IDH wild-type, the tumor should be considered as having molecular features of glioblastoma.2 Copy number variations can also further clarify or support diagnosis and provide information useful for prognosis.

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Genome-wide methylation array

Methylation profiling provides a tumor-specific signature that can be used to establish and clarify the diagnosis of CNS tumors and serves as an important complement to sequencing or chromosomal microarray results. Methylation profiling has been recognized as a molecular biomarker for CNS tumors by the 2021 5th World Health Organization (WHO) Classification and has been recommended as an ancillary tool to assist in diagnosis for tumor types that can be substratified by methylation, and on diagnostically difficult cases.

Research has shown that methylation analysis of CNS tumors could change the diagnosis in up to 12% of cases.5

Our first-in-class, clinical genome-wide DNA methylation array provides the methylation profile and MGMT promoter methylation status of CNS tumors through the use of the Illumina Infinium MethylationEPIC v2.0 combined with the National Institutes of Health-developed, AI-powered CNS tumor classifier algorithm v.2.0, the Mayo Clinic-developed nearest-neighbors assisted unsupervised analysis (NN method), and the open-source mgmtstp27 R package.

The NIH-developed, proprietary NCI/Bethesda Central Nervous System (CNS) Tumor Classifier v2.0 algorithm generates tumor classification at family and class levels based on its unique epigenetic signature. This signature reflects the tumor’s cell of origin as well as acquired methylation changes, and is a powerful tumor classification tool. By comparing tumor methylation patterns against large, validated reference datasets, this approach can resolve diagnostically difficult cases and uncover clinically meaningful entities that may not be apparent using conventional methods alone.

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MGMT promoter methylation status

MGMT promoter methylation status has prognostic value for glioblastoma patients and can assist in predicting therapeutic response.

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Additional DNA testing

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References
  1. Praska C, Kollmeyer T, Barr Fritcher E, et al. Clinical utility of combined next generation sequencing and chromosomal microarray analysis for the diagnosis and management of adult gliomas. Neuro Oncol. 2020;22(Suppl 2):ii174. doi:10.1093/neuonc/noaa215.725
  2. WHO Classification of Tumours Editorial Board, Central nervous system tumours. Lyon (France): International Agency for Research on Cancer, 5th ed., vol. 6, 2021.
  3. Brat DJ, Aldape K, Colman H, et al. cIMPACT-NOW update 3: recommended diagnostic criteria for “Diffused astrocytic glioma, IDH-wildtype, with molecular features of glioblastoma, WHO grade IV.” Acta Neuropathol. 2018 Nov;136(5):805-810.
  4. Central Nervous System Cancers. National Comprehensive Cancer Network Clinical Practice Guidelines in Oncology. Version 2.2025: Aug. 28, 2025. https://www.nccn.org/professionals/physician_gls/pdf/cns.pdf
  5. Morgan K. Diagnosing Central Nervous System tumors more Precisely with Methylation Marks. National Cancer Institute. NCI-Connect. https://www.cancer.gov/rare-brain-spine-tumor/blog/2022/methylation-marks. Pub. April 2022. Accessed March 2026.
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