An Exploratory Application of a Central Nervous System (CNS) Tumor Methylation Classifier in Ovarian Neuroectodermal...

Ovarian neuroectodermal tumors (NETs) are rare malignancies with unclear diagnostic criteria and challenging treatment. We aimed to assess the utility of DNA methylation in the diagnostic classification and prognostic stratification of ovarian NETs. This retrospective study included 15 patients diagnosed with ovarian NETs at Peking Union Medical College Hospital between 2010 and 2024. Paraffin-embedded tumor tissues from all patients underwent clinicopathologic review, DNA methylation microarray assay, EWSR1 fluorescence in situ hybridization, and immunohistochemistry. The median age at diagnosis of ovarian NETs was 19 years (range, 9-73 years). These tumors often displayed nonspecific clinical manifestations and were frequently diagnosed at an advanced stage. Morphologic diagnosis included 3 medulloblastoma, 1 neuroblastoma, 3 embryonal tumors with multilayered rosettes (ETMRs), 3 ependymomas, 1 high-grade glioma, 1 gliosarcoma, 1 low-grade neuronal-glial tumor, and 2 tumors that cannot be specified. A teratoma background was present in 73.3% (11/15) of the cases. None of the tumors exhibited EWSR1 gene rearrangement. Methylation classification was consistent with morphologic diagnosis in 30% of patients (5/15). A novel ETMR, non-C19MC-altered type ovarian tumor was identified in 3 patients. The median follow-up period of all patients was 14.9 months (range, 2.1-216.4 months), during which 60.0% of patients experienced recurrence or disease progression, and the mortality rate was 33.3%. Patients with ETMR non-C19MC-altered subtype and unmatched tumors exhibited extremely poor outcomes, with 80% (4/5) mortality within 12 months. DNA methylation profiling classified a subset of ovarian NETs into molecular subtypes resembling those of central nervous system (CNS) tumor counterparts, with corresponding prognostic similarities. Leveraging the CNS tumor methylation classifier to diagnose peripheral neuroectodermal tumors may offer critical clinical insights for these rare malignancies, enabling molecular subtyping, prognostication, and alignment with CNS-targeted therapeutic strategies.