CNS & pituitary tumors

Contributed by Jared T. Ahrendsen, M.D., Ph.D.

Contributed by Jared T. Ahrendsen, M.D., Ph.D.

• Ganglioglioma:
  • Biphasic tumor with variable mixture of mature appearing ganglion-like cells and atypical glial cells
  • Ganglion-like cells demonstrate dysmorphic features:
    • Binucleation
    • Neuron clustering (kissing neurons)
    • Cytomegaly with ballooning cytoplasm
    • Peripheral accumulation of Nissl substance
    • Lack of organized cytoarchitecture (Acta Neuropathol 1994;88:166)
  • Atypical glial cells are hyperchromatic, moderately enlarged and resemble those of fibrillary astrocytomas, pilocytic astrocytoma or oligodendroglioma (Hum Pathol 2016;49:107, Clin Interv Aging 2014;9:1981)
  • Eosinophilic granular bodies more common than Rosenthal fibers (Acta Neuropathol 1994;88:166)
  • Other common findings:
    • Dystrophic calcifications
    • Perivascular lymphoid infiltrates
    • Prominent capillary network
    • Low to absent mitotic activity (J Neuropathol Exp Neurol 2002;61:575)
  • Compact growth but microscopic infiltration can be seen along the tumor edge (Acta Neuropathol 2014;128:39, Nat Rev Neurol 2016;12:732)
  • Rare cases with anaplastic features (anaplastic ganglioglioma) have been reported:
    • Tumors with ganglioglioma-like histology and increased mitoses, microvascular proliferation, necrosis
    • Many reported cases lack molecular analyses to exclude other high grade gliomas (J Neuropathol Exp Neurol 2016;75:971, Neuro Oncol 2017;19:678)
    • Anaplastic ganglioglioma is a term that should be used with caution, especially if complete molecular characterization is not available (Neuropathol Appl Neurobiol 2022;48:e12847)
• Gangliocytoma:
  • Generally similar to that of ganglioglioma except lacking atypical neoplastic glial cells
  • Composed almost entirely of large, dysmorphic ganglion cells (as described above), often arranged in irregular clusters

Contributed by Jared T. Ahrendsen, M.D., Ph.D.

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A 15 year old patient presents with chronic seizures that are refractory to medical management. Magnetic resonance imaging (MRI) of the brain reveals a cystic lesion with an area of solid enhancement located in the medial temporal lobe. Surgical resection was performed, revealing the histology shown above. What is the most likely diagnosis?

1. Ganglioglioma
2. Glioblastoma
3. Oligodendroglioma
4. Pilocytic astrocytoma
5. Subependymal giant cell astrocytoma

A. Ganglioglioma. This clinical scenario describes classic features of ganglioglioma: a young patient with refractory seizures who presents with a cystic mass with enhancing mural nodule and histology that demonstrates a biphasic tumor with admixed neoplastic glial cells and dysmorphic ganglion-like cells. Other common histologic findings include perivascular lymphocytes, calcifications and eosinophilic granular bodies. Glioblastoma (answer B) is a high grade, infiltrating neoplasm composed of markedly atypical glial cells with increased mitoses, necrosis and microvascular proliferation. Oligodendroglioma (answer C) generally occurs in adults with brain imaging that shows an infiltrative process and histologic examination that reveals tumor cells with perinuclear halos (fried egg appearance). Pilocytic astrocytoma (answer D) usually occurs in the cerebellum or optic pathway and is characterized by bipolar glial cells with hair-like (piloid) processes, Rosenthal fibers, eosinophilic granular bodies and degenerative atypia. Subependymal giant cell astrocytoma (answer E) is a tumor found almost exclusively in patients with tuberous sclerosis; it is generally located near the ventricles and is composed of large, atypical, multinucleated astrocytes without a population of neoplastic ganglion-like cells.

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Reference: Gangliocytoma & ganglioglioma

A 10 year old patient with chronic epilepsy underwent surgical resection of a temporal lobe mass. The histology was compatible with ganglioglioma, WHO grade 1. What is the most likely molecular alteration present in this tumor?

1. BRAF V600E mutation
2. H3 K27M mutation
3. IDH1 R132H mutation
4. NF1 mutation
5. NF2 mutation

A. BRAF V600E mutation. This is the most common alteration observed in ganglioglioma. H3 K27M mutation (answer B) is a characteristic molecular alteration of diffusely infiltrating midline gliomas (such as diffuse intrinsic pontine glioma). IDH1 R132H (answer C) is the most common IDH mutation, which occurs in oligodendrogliomas and infiltrating astrocytomas. NF1 alterations (answer D) are commonly seen in pilocytic astrocytomas of the optic pathway (i.e., optic pathway glioma). NF2 mutations (answer E) are common in meningiomas and schwannomas

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Reference: Gangliocytoma & ganglioglioma