Primary Intracranial Tumors Overview

Primary Intracranial Tumors

• Intra-axial tumors originate from the brain parenchyma (neural axis)
• Glial tumors (gliomas): most common primary brain tumors, can be either infiltrative or circumscribed/diffusely
  • Astrocytoma (infiltrative)
  • Ependymoma
  • Oligodendroglioma
• Choroid plexus tumors:
  • Choroid plexus papilloma
  • Choroid plexus carcinoma
• Neuronal and Glioneuronal tumors:
  • Central neurocytoma
  • Ganglioglioma
• Embryonal tumors (primitive tumors):
  • Medulloblastoma (cerebellum)
  • CNS neuroblastoma (and other embryonal tumors of the cerebellar hemispheres)
• Primary CNS lymphoma
• Germ cell tumors: located in midline brain structures.
  • Germinoma of the pineal body
  • Tumors of the pituitary gland and the sellar region
    • Pituitary adenoma (pituitary neuroendocrine tumor)
    • Craniopharyngioma
• Meningeal tumors (extra-axial): meningiomas

Secondary Tumors (Metastasis)

• Grading of brain tumors: histological grading is used to predict tumor behavior and guide treatment (chemotherapy and radiation)
• WHO Grade 1: biologically benign, low proliferative potential, potential for cure with surgery alone
• WHO Grade 2: low-grade malignancy or locally malignant, generally infiltrative, can recur
• WHO Grade 3: frank malignancy; histological evidence of malignancy, nuclear atypia, brisk mitotic activity; often treated with adjuvant radiation and/or chemotherapy
• WHO Grade 4: highly malignant, cytologically malignant, rapid evolution, fatal outcomes, widespread infiltration and craniospinal dissemination; Example tumors include glioblastoma, some embryonal neoplasms (medulloblastomas), and many sarcomas; often spread by cerebrospinal fluid (CSF) dissemination

Astrocytomas

• Incidence: approximately 80% of primary brain tumors in adults
• Site of origin: primarily in cerebral hemispheres
• Types:
  • Well-circumscribed astrocytomas (Grade I): good prognosis after surgery, no recurrence or grade increase; pilocytic astrocytoma is a prime example
  • Diffusely infiltrating astrocytomas (Grade II, III, IV): often infiltrate surrounding brain tissue, higher-grade tumors have increased risk of progression to higher grades, may disseminate into cerebrospinal fluid (CSF)

Ependymoma

• Tissue of origin: ependymal cells (lining ventricles)
• Sites:
  • Infancy/childhood: 4th ventricle, often causing hydrocephalus (obstruction); poor prognosis due to location
  • Adults: spinal cord (myxopapillary ependymoma)
• Microscopic features: tumor cells with oval nuclei, ependymal canals, true or pseudo-rosettes (perivascular); important for diagnosis

Oligodendrogliomas

• Site of origin: cerebral hemispheres (frontal and temporal regions primarily)
• Age: often occurs in adults
• Gross appearance: well-circumscribed mass
• Microscopic features: uniform cells with clear halos of cytoplasm around central nuclei, areas of calcification

Embryonal (Primitive) Tumors

• Definition: WHO grade IV tumors
• Types:
  • Medulloblastoma (most common type of primitive CNS tumor) with origin in cerebellum; typically affects infants and young children
• CNS Neuroblastoma: primitive tumors of the cerebral hemispheres

Meningiomas

• Tissue of origin: meningothelial cells (within arachnoid villi)
• Common sites: parasagittal areas, falx cerebri, sphenoid ridge
• Age: frequently in middle-aged adults
• Gross: well-circumscribed tumors adherent to dura matter
• Microscopic: meningothelial whorls, psammoma bodies (laminated calcifications)

Primary CNS Lymphoma

• Incidence/predisposing factors: often associated with late-stage AIDS
• Gross picture: usually periventricular, can be nodular or diffuse
• Microscopic picture: large cell B-cell non-Hodgkin's lymphomas
• Prognosis: poor, with a mean survival time of around 18 months

Metastatic Tumors

• Spread: usually via bloodstream
• Common tumors: frequently involve leptomeninges (carcinomatous meningitis); examples include leukemia (in relapse), lung, breast, melanoma, kidney, and gastrointestinal cancers

This quiz covers the key concepts related to primary intracranial tumors, including their classifications such as glial tumors, choroid plexus tumors, and embryonal tumors. Understand the various types, their origins, and characteristics. Test your knowledge on the differentiation between intra-axial and extra-axial tumors.