Case of the Week
Section Editors: Matylda Machnowska1 and Anvita Pauranik2
1University of Toronto, Toronto, Ontario, Canada
2BC Children's Hospital, University of British Columbia, Vancouver, British Columbia, Canada
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January 19, 2023
Polymorphous Low-Grade Neuroepithelial Tumor of the Young (PLNTY)
•Background:
- Polymorphous low-grade neuroepithelial tumor of the young (PLNTY) is a newly classified tumor in the 2021 World Health Organization brain tumor classification and is categorized under pediatric-type low-grade diffuse gliomas. It was first described in 2017.
- PLNTY represents a nonneuronal and nonependymal subtype of low-grade neuroepithelial tumors.
•Clinical Presentation:
- Most present in children and young adults with a median age of 17.5 years with no predilection for males or females
- Often cause epilepsy that is early in onset and can be resistant to antiepileptics; may also present with headache, or can be an incidental finding
- Behave similarly to a grade I CNS tumor
•Key Diagnostic Features:
- Well-circumscribed with heterogeneous intralesional signal and peripheral cystic components
- Macroscopic calcifications located centrally within the lesion
- Temporal lobe location (although lesions have been reported in parietal, frontal, and occipital lobes)
- Histopathologic analysis and molecular characterization will typically show calcifications, intense CD34 immunoreactivity, and mutually exclusive BRAF mutations or FGFR2/3 fusions (both of which activate the MAP kinase pathway)
•Differential Diagnosis:
- Dysembryoplastic neuroepithelial tumor (DNET): Wedge- or triangular-shaped, hypointense on T1, and hyperintense on T2/FLAIR with thin septations producing characteristic “bubbly” appearance
- Pleomorphic xanthoastrocytoma (PXA): Originate from the cortex with attachment to the leptomeninges and may have leptomeningeal enhancement, cystic and solid enhancing mass, perilesional edema, and, rarely, calcifications
- Ganglioglioma: Mixed solid and cystic appearance with homogeneous enhancement of the solid portion; can have calcification and/or increased rCBV
- Calcified low-grade astrocytoma: Most do not present with this type of appearance or in this location
- Oligodendroglioma: Typically present in older population (40–60 years of age) with frontal lobe location, less well-defined gyriform calcification, 1p19q codeletion, and poorly defined border
•Treatment:
- Surgical resection of the tumor is curative and is associated with a low recurrence rate.
- Preoperative functional MRI may provide a safe approach to surgical resection without completing intraoperative language mapping.