Polymorphous low grade neuroepithelial tumor of the young

Polymorphous low-grade neuroepithelial tumor of the young (PLNTY) is an epileptogenic tumor of children and young adults.

Terminology

First described in 2016 ¹, polymorphous low-grade neuroepithelial tumor of the young has been recently included in the new family of "pediatric-type" low-grade diffuse gliomas in the 5^th Edition (2021) WHO brain tumor classification ² (WHO grade 1 tumor).

Epidemiology

Polymorphous low-grade neuroepithelial tumor of the young mainly occurs in children and young adults ³.

Clinical presentation

Most of the patients present with seizures resistant to anti-epileptogenic drugs ³.

Pathology

Location

Polymorphous low-grade neuroepithelial tumor of the young commonly arises from the cortex and in the temporal lobes, although other locations have been reported (such as frontal, parietal, and occipital lobes) ^3,4.

Microscopic appearance, immunochemistry and genetics

Polymorphous low-grade neuroepithelial tumor of the young is typically characterized by oligodendroglioma-like cellular elements, calcifications, and a strong CD34 immunopositivity. Moreover, it frequently shows the mutation of BRAF V600E gene and fibroblast growth factor receptors 2 and 3, all of them involved in the regulation of the MAPK oncogenic pathway ^3-5.

Radiographic features

Polymorphous low-grade neuroepithelial tumors of the young display a solid or partially cystic appearance with unclear margins. It usually does not produce a significant mass effect ^3-5.

CT

Polymorphous low-grade neuroepithelial tumor of the young may appear as a hypo- or hyperdense mass, frequently calcified ^3-5.

MRI

Reported signal characteristics include

• T1: iso- or hypointense

• T2/FLAIR: heterogeneous hyperintensity with the "salt and pepper" sign (likely due to calcifications)

• T2*/SWI: "blooming" for calcifications

• DWI/ADC: no restricted diffusion

• T1 C+ (Gd): slight or no enhancement ^3-5.

Treatment and prognosis

Surgery is curative and therefore the prognosis is good ^3-5. 

Differential diagnosis

Differential diagnosis generally includes other epileptogenic entities ³.

• dysembryoplastic neuroepithelial tumors: clear margins and a "soap-bubble" appearance

• pleomorphic xanthoastrocytoma (PXA): dural tail sign and significant contrast enhancement

• ganglioglioma: cystic mass with an intense enhancing mural nodule; often no calcifications are seen

• oligodendroglioma: often occurs in adults and arises in the frontal lobes; calcifications are in most cases "ribbon-like" or peripherally distributed

• focal cortical dysplasia: characterized by the thickening of the cortex, blurring of white matter-grey matter junction and the transmantle sign