CNS & pituitary tumors

Gliomas, glioneuronal tumors, and neuronal tumors

Neuronal and mixed neuronal-glial tumors

Rosette forming glioneuronal tumor (RGNT)


Editorial Board Member: P.J. Cimino, M.D., Ph.D.
Deputy Editor-in-Chief: Chunyu Cai, M.D., Ph.D.
Eman Abdelzaher, M.D., Ph.D.

Last author update: 14 December 2023
Last staff update: 14 December 2023

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PubMed Search: Rosette forming glioneuronal tumor

Eman Abdelzaher, M.D., Ph.D.
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Cite this page: Abdelzaher E. Rosette forming glioneuronal tumor (RGNT). PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/cnstumorRGNT.html. Accessed March 28th, 2024.
Definition / general
Essential features
  • Rare, slow growing glioneuronal neoplasm (Neurooncol Adv 2020;2:vdaa116)
  • Preferentially affects young adults, adolescents and children
  • Occurs throughout CNS with predilection for fourth ventricle region
  • 2 distinct histological components: neurocytic with distinctive rosettes and glial areas
  • Recently, rosette forming glioneuronal tumors (RGNTs) with malignant behavior have been reported (Oncotarget 2017;8:109175)
Terminology
ICD coding
  • ICD-O: 9509/1 - rosette forming glioneuronal tumor
  • ICD-11: 2A00.21 & XH2JU8 - mixed neuronal glial tumors & rosette forming glioneuronal tumor
Epidemiology
  • Rare; specific population based incidence rates are not available
  • Preferentially affects young adults, adolescents and children; mean age at diagnosis is 28 years (range: 2 - 81 years) (Oncotarget 2017;8:109175)
  • No gender predilection (Oncotarget 2017;8:109175)
Sites
Pathophysiology
Etiology
Clinical features
Diagnosis
  • Neuroimaging: magnetic resonance imaging (MRI) is the preferred modality, computed tomography (CT) (Br J Neurosurg 2012;26:668)
  • Biopsy
  • WHO essential and desirable diagnostic criteria
    • Essential diagnostic criteria (presence of the following 3 characteristics)
      • Biphasic histomorphology with a neurocytic component and a glial component
      • Uniform neurocytes forming rosettes or perivascular pseudorosettes associated with synaptophysin expression
      • (For unresolved lesions) small biopsies showing only 1 tumor component (neurocytic or glial) and a methylation profile of rosette forming glioneuronal tumor
    • Desirable diagnostic criteria
      • FGFR1 mutation with co-occurring PIK3CA or NF1 mutation
Radiology description
  • CT (Oncotarget 2017;8:109175)
    • Hypodense midline mass
    • Calcification (< 25%)
  • MRI (Oncotarget 2017;8:109175)
    • Relatively circumscribed midline mass, solid or cystic - solid pattern (47%), cystic pattern (35%) and mixed cystic solid pattern (18%)
    • T1 hypointense, T2 hyperintense
    • Variable contrast enhancement
      • Heterogeneous (44.7%), rim (23.7%) or focal (7.9%) enhancement
      • No enhancement (25%)
Radiology images

Contributed by Eman Abdelzaher, M.D., Ph.D.
CT without contrast

CT without contrast

CT with contrast

CT with contrast



Images hosted on other servers:
Cerebellar and fourth ventricular RGNT

Cerebellar and fourth ventricular RGNT

MRI of cerebellar vermis RGNT

MRI of cerebellar vermis RGNT

Third ventricle RGNT

Third ventricle RGNT

MRI of aqueduct and thalamic RGNT

MRI of aqueduct and thalamic RGNT

Postcontrast T1 weighted MRI image

Postcontrast T1 weighted MRI

MRI of pineal region and third ventricle RGNT

MRI of pineal region and third ventricle RGNT

Prognostic factors
Case reports
Treatment
Clinical images

Images hosted on other servers:
Right frontal exophytic lesion

Right frontal exophytic lesion

Spinal RGNT, intraoperative picture

Spinal RGNT, intraoperative picture

Gross description
  • Well demarcated, soft, gelatinous
Frozen section description
Frozen section images

Images hosted on other servers:
Circle‐like arrangement of the small and uniform nuclei

Moderately cellular and hypocellular areas

Microscopic (histologic) description
  • Circumscribed, may show limited infiltration of surrounding parenchyma
  • Biphasic with 2 distinct histological components: neurocytic and glial
  • Neurocytic component
    • Consists of uniform neurocytes forming neurocytic rosettes or perivascular pseudorosettes (Clin Case Rep 2021;9:e04355)
    • Neurocytes have small round nuclei with fine stippled chromatin and scant cytoplasm
    • Neurocytic rosettes are small with ring-like arrangement of neurocytes around delicate eosinophilic neuropil cores; may be arrayed in a cribriform pattern (Brain Pathol 2007;17:308)
    • Perivascular pseudorosettes are narrow and formed of neurocytes with delicate cell processes radiating towards central vessels
    • Neurocytic elements may lie unanchored in partly microcystic, mucinous matrix and, when sectioned longitudinally, may show a linear arrangement (Brain Pathol 2007;17:308)
  • Glial component
    • Typically, dominant component and low grade
    • Resembles pilocytic astrocytoma with piloid and oligodendroglia-like cells
    • Astrocytic tumor cells are spindle to stellate in shape, with elongated or oval nuclei and cytoplasmic processes forming a compact to loosely textured fibrillary background (Acta Neuropathol 2019;138:497)
    • May show oligodendroglia-like cells with perinuclear haloes arranged in microcystic pattern or diffuse sheets (Brain Pathol 2007;17:308)
  • Mitoses and necrosis absent or rare, atypia absent or minimal (Oncotarget 2017;8:109175, Acta Neuropathol 2019;138:497)
  • Rosenthal fibers, eosinophilic granular bodies (EGBs), microcalcifications and hemosiderin deposits may be seen (Brain Pathol 2007;17:308, Acta Neuropathol 2019;138:497)
  • Blood vessels may be ectatic, hyalinized, thrombosed or show glomeruloid microvascular proliferation (Oncotarget 2017;8:109175)
  • Rarely, dysmorphic neurons may be seen in the glial regions (Brain Pathol 2007;17:308)
Microscopic (histologic) images

Contributed by Eman Abdelzaher, M.D., Ph.D.
Biphasic neurocytic and glial components

Biphasic neurocytic and glial components

Biphasic neurocytic and pilocytic components

Biphasic neurocytic and pilocytic components

Neurocytic rosettes Neurocytic rosettesr

Neurocytic rosettes

Neurocytes with stippled chromatin

Neurocytes with stippled chromatin


Neurocytic rosettes and pseudorosettes Neurocytic rosettes and pseudorosettes

Neurocytic rosettes and pseudorosettes

Cribriform pattern Cribriform pattern

Cribriform pattern

Microcystic pattern

Microcystic pattern


Microcystic pattern

Microcystic pattern

Pilocytic-like area

Pilocytic-like area

Piloid and oligodendroglia-like cells

Piloid and oligodendroglia-like cells


Synaptophysin Synaptophysin

Synaptophysin

Synaptophysin Synaptophysin

Synaptophysin

Neurocytic cells of RGNT are negative for GFAP

Negative neurocytes by GFAP


Glial fibrillary acidic protein (GFAP) Glial fibrillary acidic protein (GFAP)

Glial fibrillary acidic protein (GFAP)

Epithelial membrane antigen (EMA) RGNT showing negative immunostaining for EMA

Epithelial membrane antigen (EMA)

Ki67

Ki67

Cytology description
  • Cellular smears
  • Neurocytic cells have uniform round nuclei with delicate chromatin, inconspicuous nucleoli and scant cytoplasm; neurocytic rosettes with fibrillar cores may be seen (Acta Cytol 2021;65:111)
  • Glial, fibrillary fragments showing piloid astrocytes with elongated nuclei and coarse bipolar processes
  • Dense extracellular mucoid substance
  • No atypia
Cytology images

Images hosted on other servers:
Neurocytic rosettes

Neurocytic rosettes

Positive stains
Electron microscopy description
Molecular / cytogenetics description
Molecular / cytogenetics images

Images hosted on other servers:
RGNT, DNA methylation profiling

RGNT, DNA methylation profiling

RGNT, recurrent genetic alterations

RGNT, recurrent genetic alterations

Videos

WHO classification of CNS tumors: glioneuronal tumors

Sample pathology report
  • Brain mass lesion, fourth ventricle, gross total resection:
    • Rosette forming glioneuronal tumor, CNS WHO grade 1
    • Molecular genetics: methylation profile of rosette forming glioneuronal tumor
Differential diagnosis
Board review style question #1

A 15 year old girl presented with a headache. MRI showed a posterior fossa mass lesion epicentered on the cerebellar vermis. Resection of the tumor was done and the histopathological features of the tumor are shown above. Which of the following is a typical genetic finding in this tumor?

  1. 1p / 19q codeletion
  2. BRAF alterations
  3. FGFR1 mutations
  4. PRKCA gene fusion
Board review style answer #1
C. FGFR1 mutations. FGFR1 hotspot mutations are typical of rosette forming glioneuronal tumors (RGNTs). Answer B is incorrect because RGNTs lack BRAF alterations. Answer D is incorrect because PRKCA gene fusion (mainly SLC44A1::PRKCA) is the hallmark of papillary glioneuronal tumors (PGNTs). Answer A is incorrect because 1p / 19q codeletion is characteristic of oligodendroglioma.

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Reference: Rosette forming glioneuronal tumor
Board review style question #2
Rosette forming glioneuronal tumor is characterized by which of the following features?

  1. Diffuse growth pattern
  2. Exclusive supratentorial location
  3. Neurocytic rosettes with synaptophysin positive neuropil cores
  4. Papillary architecture
Board review style answer #2
C. Neurocytic rosettes with synaptophysin positive neuropil cores. Neurocytic rosettes with synaptophysin positive neuropil cores are the histologic hallmark of rosette forming glioneuronal tumors (RGNTs). Answer A is incorrect because RGNTs are generally demarcated with occasional limited infiltration of the surrounding parenchyma. Answer B is incorrect because RGNTs occur throughout the CNS with predilection to posterior fossa. Answer D is incorrect because papillary architecture is not a feature of RGNTs.

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Reference: Rosette forming glioneuronal tumor
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