CNS & pituitary tumors

Gliomas, glioneuronal tumors, and neuronal tumors

Pediatric type diffuse low grade gliomas

Polymorphous low grade neuroepithelial tumor of the young (PLNTY)


Editorial Board Member: Jared T. Ahrendsen, M.D., Ph.D.
Deputy Editor-in-Chief: Chunyu Cai, M.D., Ph.D.
Eman Abdelzaher, M.D., Ph.D.

Last author update: 5 March 2024
Last staff update: 5 March 2024

Copyright: 2022-2024, PathologyOutlines.com, Inc.

PubMed Search: Polymorphous low grade neuroepithelial tumor of the young (PLNTY)

Eman Abdelzaher, M.D., Ph.D.
Page views in 2024 to date: 583
Cite this page: Abdelzaher E. Polymorphous low grade neuroepithelial tumor of the young (PLNTY). PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/cnstumorplnty.html. Accessed April 14th, 2024.
Definition / general
  • Indolent cerebral neoplasm characterized by a strong association with seizures in young individuals, diffuse growth patterns, frequent presence of oligodendroglioma-like components, calcifications, CD34 immunoreactivity and MAPK pathway activating genetic abnormalities
  • CNS WHO grade 1
  • Recently introduced in WHO 2021 classification of CNS tumors
Essential features
  • Recently described, frequently epileptogenic, low grade neuroepithelial tumor (Acta Neuropathol 2017;133:417)
  • Typically affects children and young adults
  • Characterized by diffuse growth patterns, oligodendroglioma-like cellular components, CD34 immunopositivity and MAPK pathway activating genetic abnormalities
  • Generally, exhibits a benign clinical course (Acta Neuropathol 2017;133:417)
Terminology
  • Has been described under the generic designation of long term epilepsy associated tumors (Acta Neuropathol 2014;128:39)
  • Not recommended by WHO
    • Diffuse glioneuronal tumor
    • Diffuse or nonspecific form of dysembryoplastic neuroepithelial tumor
    • Massively calcified low grade glioma
ICD coding
  • ICD-O: 9413/0 - polymorphous low grade neuroepithelial tumor of the young
  • ICD-11: 2A00.2Y - other specified tumors of neuroepithelial tissue of brain
Epidemiology
Sites
Pathophysiology
  • Aberrant CD34 expression possibly reflects an origin from developmentally dysregulated neural precursors (Acta Neuropathol 1999;97:481)
  • Somatic MAPK pathway activating genetic abnormalities (particularly BRAF mutations or FGFR fusions) definitely drive the pathogenesis of PLNTY; however, the specific mechanisms by which these genetic alterations contribute to the development of PLNTY are not clear (Acta Neuropathol 2017;133:417)
Etiology
Diagrams / tables

Images hosted on other servers:
Prototypical PLNTY

Prototypical PLNTY

Clinical features
Diagnosis
  • Neuroimaging: MRI and CT (Acta Neurol Belg 2023;123:327)
  • Biopsy
  • WHO essential and desirable diagnostic criteria
    • Essential diagnostic criteria (presence of the following 6 characteristics)
      • Diffuse growth pattern (at least regionally)
      • Oligodendroglioma-like components (may be minor)
      • Few (if any) mitotic figures
      • Regional CD34 expression by tumor cells and by ramified neural cells in associated cerebral cortex
      • IDH wild type status
      • Unequivocal expression of BRAF p.V600E on immunohistochemical assessment or molecular diagnostic evidence of BRAF V600E mutations, FGFR2 or FGFR3 fusions or potentially other MAPK pathway driving genetic abnormalities
    • Desirable diagnostic criteria
      • Conspicuous calcification (characteristic, although not constant)
      • Absence of 1p / 19q codeletion
Radiology description
Radiology images

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FLAIR, CT scan and T1 postcontrast

FLAIR, CT scan and T1 postcontrast

Radiological variability in CT and MRI

Radiological variability in CT and MRI

Prognostic factors
Case reports
Treatment
Clinical images

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Operative view of PLNTY

Operative view

Gross description
  • Unencapsulated, indistinctly demarcated from normal brain
  • Soft to friable, gray-white masses
Microscopic (histologic) description
Microscopic (histologic) images

Contributed by Eman Abdelzaher, M.D., Ph.D. and Jared T. Ahrendsen, M.D., Ph.D.
Diffuse growth pattern

Diffuse growth pattern

Diffuse growth pattern of oligodendroglioma-like cells Diffuse growth pattern of oligodendroglioma-like cells

Diffuse growth pattern of oligodendroglioma-like cells

Oligodendroglioma-like cells with mild nuclear pleomorphism

Oligodendroglioma-like cells with mild nuclear pleomorphism

Calcification

Calcification


Oligo-like features

Oligo-like features

Dystrophic calcifications

Dystrophic calcifications

Polymorphic tumor cells Polymorphic tumor cells

Polymorphic tumor cells

Olig2 diffusely positive

Olig2 diffusely positive

Strong diffuse CD34 expression

Strong, diffuse CD34 expression


CD34 CD34

CD34

CD34 in tumor cells and ramified neural cells

CD34 in tumor cells and ramified neural cells

GFAP GFAP

GFAP

Ki67

Ki67

Cytology description
  • PLNTY cannot be identified on cytological grounds alone
  • Intraoperative smear preparations may show
    • Tumor cells with rounded nuclei and devoid of cytoplasm
    • Tumor cells with irregular nuclear contours and cytoplasmic processes
    • Tumor cells attached to blood vessels in a pseudorosette fashion (Acta Neuropathol 2017;133:417)
Cytology images

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Vague perivascular pseudorosetting

Vague perivascular pseudorosetting

Positive stains
Molecular / cytogenetics description
Molecular / cytogenetics images

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Molecular and clinical findings

Molecular and clinical findings

FGFR fusions in PLNTY

FGFR fusions

Distinct methylation signature

Distinct methylation signature

Genome wide copy number changes

Genome wide copy number changes

Videos

PLNTY, case 7

Surgical resection of PLNTY
(Acta Neurol Belg 2023;123:327)

Sample pathology report
  • Brain mass lesion, temporal lobe, gross total resection:
    • Polymorphous low grade neuroepithelial tumor of the young (PLNTY), CNS WHO grade 1
    • Molecular genetics: evidence of BRAF V600E mutations, FGFR2 or FGFR3 fusions or potentially other MAPK pathway driving genetic abnormalities
Differential diagnosis
Board review style question #1

A 14 year old boy presented with refractory epilepsy. MRI showed a right temporal cystic and solid nonenhancing mass lesion. The mass was surgically resected and histopathological examination showed a low grade tumor composed of oligodendroglioma-like tumor cells arranged in a diffuse fashion as shown in the image above. Immunohistochemistry for CD34 showed regional positivity associated with positive ramified neurons in the adjacent cortex. Which of the following molecular events is characteristic of this tumor?

  1. 1p / 19q codeletion
  2. IDH mutation
  3. MAPK pathway activating abnormalities
  4. PRKCA gene fusion
Board review style answer #1
C. MAPK pathway activating abnormalities. PLNTY is characterized by a strong association with seizures in young individuals, diffuse growth patterns, frequent presence of oligodendroglioma-like components and CD34 immunoreactivity. It is molecularly characterized by MAPK pathway activating genetic abnormalities. Answers A and B are incorrect because PLNTY does not harbor IDH mutations or 1p / 19q codeletion. Answer D is incorrect because PRKCA gene fusion (mainly SLC44A1::PRKCA) is the hallmark of papillary glioneuronal tumor (PGNT).

Comment Here

Reference: Polymorphous low grade neuroepithelial tumor of the young (PLNTY)
Board review style question #2
Polymorphous low grade neuroepithelial tumor of the young (PLNTY) is characterized by which of the following features?

  1. Absence of calcification
  2. CD34 negative immunostaining
  3. Clinical presentation of headache
  4. Oligodendroglioma-like components
Board review style answer #2
D. Oligodendroglioma-like components. PLNTY is characterized by frequent presence of oligodendroglioma-like components. Answer A is incorrect because calcification is a frequent finding in PLNTY. Answer B is incorrect because CD34 immunoreactivity is a characteristic finding in PLNTY. Answer C is incorrect because PLNTY is characterized by a strong association with seizures in young individuals.

Comment Here

Reference: Polymorphous low grade neuroepithelial tumor of the young (PLNTY)
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