Case of the Week

Background:

Polymorphous low-grade neuroepithelial tumor of the young (PLNTY) is an indolent, WHO grade 1 cerebral tumor characterized by refractory seizures, frequent oligodendroglial-like histologic components, calcification, CD34 immunoreactivity, and mitogen-activated protein kinase (MAPK) pathway–activating genetic alterations. The temporal lobe is a common location. Integrative molecular profiling reveals a distinct DNA methylation signature for PLNTYs, along with frequent genetic abnormalities involving either B-Raf proto-oncogene (BRAF) or fibroblast growth factor receptors 2 and 3 (FGFR2, FGFR3). These findings suggest that PLNTY represents a distinct biologic entity within the larger spectrum of pediatric, low-grade neuroepithelial tumors.

Clinical Presentation:

Patients commonly present with seizures but some also present with headache and dizziness or visual disturbances. Patients are of age 4–32 years. Most tumors are located in the temporal region but cases in the frontal and occipital region are also reported.

Key Diagnostic Features:

• Typical appearance: A unifocal abnormality best seen on FLAIR sequence
• Calcifications frequently appreciated on CT scan
• Temporal lobe is most common location
• Lesions are most commonly seen in cortical/subcortical location
• Cystic components are frequently seen
• Relatively infrequent contrast enhancement

Differential Diagnoses:

• Dysembryoplastic neuroepithelial tumor (DNET): cortically based, "bubbly" wedge-shaped lesion, usually no contrast enhancement, and a thin halo of hyperintense signal on FLAIR
• Papillary glioneural tumor: well-circumscribed cyst, with an avid, enhancing wall or mural nodule. The cystic component may be suppressed on FLAIR, and the solid component presents with hypo- to isointense signal on T1-weighted imaging, iso- to hyperintense signal on T2-weighted imaging, with no diffusion restriction.
• Multinodular and vacuolating neuronal tumor: Imaging findings are multiple, small, and coalescent cortical and subcortical nodules, isointense to gray matter on T1-weighted imaging, hyperintense on T2-weighted imaging and FLAIR, with no mass effect, perilesional edema, calcification, diffusion restriction, and contrast enhancement (though faint enhancement may occasionally be present)
• Central neurocytoma: intraventricular, heterogeneous, and “bubbly” mixed solid and cystic lesion, with a solid component presenting heterogeneous signal, isointense to gray matter on T1-weighted imaging, hyperintense on FLAIR, with flow voids, calcification (50% of cases) with hemorrhage, and diffusion restriction

Treatment:

• Surgery (normally gross total resection) is usually curative, though recurrences and high-grade progression have been reported.