<unk> s are a type of glioma that are believed to originate from the tripotential glial precursor cells. The term<unk> " was first coined by Bailey and Cushing in 1926 following the observation that the tumor cells are morphologically similar to oligodendrocytes. According to the new 2016 edition of WHO classification of gliomas based on histopathologic appearance and well-established molecular parameters,<unk> s are subclassified into grade II tumors including<unk>  IDH-mutant and 1p/19q-codeleted,<unk>  NOS, oligoastrocytoma NOS, and grade III tumors including anaplastic<unk>  IDH-mutant and 1p/19q-codeleted, anaplastic<unk>  NOS, and anaplastic oligoastrocytoma NOS. Genes associated with the pathogenesis of<unk>  include t[1;19][q10;p10], ATRX, NJDS, IDH1, IDH2, TERT promoter, H3 K27M (H3F3A, HIST1H3B/C), CIC, FUBP1, p53, Leu-7, TCF-12, TP53, MGMT, TP73, BRAF, EGFR, and PTEN. Common intracranial sites involved by<unk>  include cerebral hemispheres, posterior fossa, and intramedullary spinal cord. On gross pathology,<unk>  is characterized by a well-circumscribed, gelatinous, calcified, cystic, gray mass with focal hemorrhage which may expand a gyrus and remodel the skull. On microscopy, it shows a diffuse growth pattern of highly cellular lesion of monomorphic cells having rounded nucleus with atypia, speckled "salt-and-pepper" chromatin pattern and perinuclear halo resembling fried eggs, distinct cell borders, clear cytoplasm, abundant calcification and "chicken-wire" like vascularity pattern. Common causes of<unk>  include genetic mutations, some viral cause or irradiation of pituitary adenoma. On the basis of seizure, visual disturbance, and constitutional symptoms,<unk>  must be differentiated from astrocytoma, meningioma, hemangioblastoma, pituitary adenoma, schwannoma, primary CNS lymphoma, medulloblastoma, ependymoma, craniopharyngioma, pinealoma, AV malformation, brain aneurysm, bacterial brain abscess, tuberculosis, toxoplasmosis, hydatid cyst, CNS cryptococcosis, CNS aspergillosis, and brain metastasis. It constitutes about 9.4% of all CNS tumors and 5%–18% of all glial neoplasms with incidence of<unk>  and anaplastic<unk>  to be 0.32 and 0.17 cases per 100,000 individuals in the United States, respectively.<unk>  is a disease that tends to affect the middle-aged adult population mainly occurring in the 4th and 5th decade of life with median age at the time of diagnosis to be 35-47 years. Males are more commonly affected than females with the male to female ratio of approximately 1.3:1.<unk>  usually affects individuals of the Caucasian race and African American, Latin American, and Asian individuals are less likely to develop<unk> . The most potent risk factor for the development of<unk>  is family history of brain tumors. If left untreated, patients with<unk>  may progress to develop seizures, focal neurological deficits, hydrocephalus, brain herniation, intracranial hemorrhage, and ultimately death. Common complications associated with<unk>  include hydrocephalus, intracranial hemorrhage, coma, bone marrow metastasis, recurrence, venous thromboembolism, parkinsonism, and side effects of chemotherapy and radiotherapy. The overall prognosis is good but the prognosis may vary depending upon various prognostic factors such as population based estimates, clinical factors, tumor grade (II versus III), mechanism of chemosensitivity, and molecular markers such as 1p/19q-codeletion, IDH1/2 mutation, and TERT promoter mutations. Symptoms associated with<unk>  include seizure, headache, nausea, vomiting, vertigo, visual loss, diplopia, strabismus, muscle weakness, numbness, speech difficulties, mood disturbances, personality changes, memory problems, low energy, fatigue, urge to sleep, loss of interest in daily activities, abulia, lack of spontaneity, loss of consciousness with syncope (few  tonic-clonic jerks), and classic triad of headache, nausea, and papilledema due to raised intracranial pressure. Findings on CT scan suggestive of<unk>  are round or oval, marginated, hypo- to isodense mass with hemorrhage, ribbon-like calcification, ill-defined enhancement following intravenous contrast administration, pressure erosion/remodelling of overlying skull, and marked ventricular enlargement suggestive of hydrocephalus. On brain MRI,<unk>  is characterized by a mass which is typically hypointense on T1-weighted images and hyperintense on T2-weighted images. Calcification is observed as areas of "blooming" on T2 decay component of MRI. Other imaging studies for<unk>  include MR spectroscopy (dominant N-acetyl aspartate peak, increased choline levels and decreased NAA levels with a myo-inositol peak), MR perfusion (increased "chicken wire" network of vascularity, which results in elevated relative cerebral blood volume), PET scan (to differentiate between<unk>  from anaplastic<unk>  and tumor recurrence from tumor necrosis), and bone scan (bone metastasis). Other diagnostic studies for<unk>  include biopsy (homogeneous, compact, rounded cells with distinct borders and clear cytoplasm surrounding a dense central nucleus and perinuclear halo) and fluorescent in-situ hybridization (FISH) technique (deletions of chromosome 1p and 19q). The predominant therapy for<unk>  is surgical resection. Adjunctive chemotherapy and radiation are required. Supportive therapy for<unk>  includes anticonvulsants and corticosteroids.
Oligodendroglioma
Gemistocytic astrocytoma
Protoplasmic astrocytoma
Astrocytoma
Medulloblastoma
Ameloblastoma
Oligoastrocytoma
Ganglioglioma