Polymorphous low-grade neuroepithelial tumor of the young (PLNTY) is an epileptogenic tumor of children and young adults. They are often considered part of the heterogeneous group of tumors known as long-term epilepsy-associated tumors (LEATs).
On this page:
Terminology
First described in 2016 1, polymorphous low-grade neuroepithelial tumor of the young has been included in the new family of "pediatric-type" low-grade diffuse gliomas in the 5th 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 drug-refractory epilepsy 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.
-
ganglioglioma and gangliocytoma
similar appearance and location
also fairly frequently has calcifications
-
can be indistinguishable on imaging
rare
-
pleomorphic xanthoastrocytoma (PXA)
similar appearance and location
often very vivid contrast enhancement
may have a dural tail sign
-
dysembryoplastic neuroepithelial tumor (DNET)
soap-bubble appearance and bright rim sign
enhancement less common and less intense if present
-
usually occurs in middle aged adults
less commonly arises in the temporal lobes
calcifications are common, tend to be "ribbon-like" or peripherally distributed
-
characterized by the thickening of the cortex,
blurring of white matter-grey matter junction and the transmantle sign
no enhancement
-
calcifying pseudoneoplasm of the neuraxis (CAPNON)
almost entirely calcified
usually extra-axial (but can be intra-axial)