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Neuronal and Glioneuronal Tumors


Ganglion Cell Tumors

Definition

  • Well - differentiated tumors of the CNS with mature neurons (ganglion cells) as a defining feature: includes ganglioglioma (ganglion cell tumor with a low-grade glial element), gangliocytoma (without a glial element), and anaplastic ganglioglioma (ganglion cells and anaplastic glial elements)

Clinical Features

Epidemiology

  • 4% of primary brain tumors, ~0.2/100,000/year

  • Most common in temporal lobe, but may arise throughout neuraxis

  • More common in children, but can be seen in any age group

Presentation

  • Associated with seizures; location-dependent symptoms

Prognosis and Treatment

  • Most are benign (WHO Grade I)

  • Rare anaplastic types are WHO Grade III

  • Most treated with surgery only (>90% 10-year survival)

  • Occasionally to recur; extremely rare to metastasize within neuraxis

  • May combine surgery, radiation for inoperative or anaplastic (WHO III) variants

Imaging Characteristics

  • Variably enhancing solid or cystic tumor (sometimes with enhancing nodular component)

  • May be calcified

Pathology

Gross

  • Demarcated or discrete tumor mass; with or without cystic changes or calcifications

Histology

  • Disorganized collection of mature ganglion cells with variable glial background

  • Clusters of mature neurons, with large nuclei, prominent nucleoli in disordered/haphazard arrangements

  • Ganglion cells may exhibit binucleation or have bizarre-appearing nuclei

  • Rosenthal fibers, eosinophilic granular bodies commonly present

  • Perivascular lymphocytes, microcalcifications also can be present

  • Must evaluate glial component for anaplasia (mitoses, microvascular proliferation, necrosis)

  • Perineuronal “satellitosis” usually absent

Immunopathology/Special Stains

  • Synaptophysin, chromogranin, neurofilament reactive neoplastic ganglion cells

  • Neuronal nuclear antibody is typically negative in neoplastic ganglion cells

  • GFAP-positive in astrocytic elements

  • Ki-67/MIB1 usually low, <2%

Main Differential Diagnoses

  • Glial neoplasms: pilocytic astrocytoma, diffuse astrocytoma entrapping cortical neurons

  • Dysembryoplastic neuroepithelial tumor (DNET)

  • Developmental lesions

  • Cortical dysplasia

  • Tuberous sclerosis

Fig 1, Ganglioglioma. This T1-weighted MRI shows an enhancing mass of the left mesial temporal lobe, a typical location for ganglioglioma.

Fig 2, Ganglioglioma. The image shows a disorganized collection of several basophilic ganglion cells with vesicular nuclei and prominent nucleoli, an eosinophilic glial background, and focal perivascular inflammation.

Fig 3, Ganglioglioma. Binucleated ganglion cells (like the one in the middle of the field ) are sometimes found but not required for the diagnosis.

Fig 4, Ganglioglioma. Brightly eosinophilic granular bodies are characteristic.

Fig 5, Ganglioglioma. Ganglion cells may show degenerative changes like the granulovacuolar change in this neuron ( center ). Microcalcifications ( left ) are also commonly found.

Fig 6, Ganglioglioma. Ganglion cells are strongly immunoreactive for neurofilament protein as shown here.

Desmoplastic Infantile Astrocytoma/Ganglioglioma

Definition

  • Benign neoplasm, but often massive, brain tumor of infancy with glial (desmoplastic infantile astrocytoma, DIA) or neuronal (desmoplastic infantile ganglioglioma, DIG) elements

Clinical Features

Epidemiology

  • <1% of primary brain neoplasms

  • Tumors of infants; majority <2 years of age

  • Roughly equal gender distribution

  • Supratentorial, usually frontoparietal and superficial (often with meningeal involvement)

Presentation

  • Compressive symptoms with hydrocephalus, bulging fontanelles, vomiting

  • May have seizures, nerve palsies, spasticity

Prognosis and Treatment

  • WHO Grade I—benign: good prognosis, rare craniospinal seeding or metastases

  • Treatment: complete resection; residual disease may remain static or regress

Imaging Characteristics

  • Large cystic hemispheric mass with internal solid enhancing nodule(s), commonly attached to dura

Pathology

Gross

  • Demarcated, large (>10 cm), cystic tumor with rubbery solid areas

  • May involve multiple lobes

Histology

  • Noninfiltrative tumor composed of spindled astrocyte-like cells

  • Small ganglion cells also seen in the DIG

  • Storiform pattern with desmoplastic reticulin-rich stroma

  • Foci of primitive and mitotically active cells may be present without implications for aggressive behavior

  • Frequently spread along Virchow-Robin spaces

Immunopathology/Special Stains

  • Reticulin (invests tumor cells)

  • Astrocytic cells strongly immune reactive for GFAP

  • Ganglion cells are synaptophysin, NeuN, neurofilament, and neuron-specific enolase positive

  • Low Ki-67 index <2%

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