Pathology of Brain Tumors Flashcards
Primary brain tumors
Where do they come from
Tumors of neuroectodermal cells
Mesenchmyal/neural crest cells
Tumors arising in the sellar region
Tumors of non-neuroectodermal origin
Primary brain tumors
Tumors of neuroectodermal cells
list
gliomas: tumors resembling of differentiated brain cells (astrocytomas,oligodendrogliomas, ependymomas, glioblastoma multiforme, choroid plexus tumor, others)
primitive neuroectodermal tumors (PNET): tumors resembling embryonic brain cells (medulloblastoma, cerebral PNET, others)
Primary brain tumors
Mesenchymal/neural crest tumors
list
tumors of brain coverings (meningiomas, others) tumors of nerve roots and peripheral nerves, usually Schwann cells (Schwannomas and neurofibromas, others)
Primary brain tumors
Mesenchymal/neural crest tumors
Tumors arising in the sellar region
tumors derived from Rathke’s pouch (pituitary adenomas, craniopharyngioma)
Primary brain tumors
Mesenchymal/neural crest tumors
Tumors of non-neuroectodermal origin
primary CNS lymphomas, germ cell tumors, etc.
Secondary tumors of the brain
list
intraparenchymal or meningeal metastases (carcinomas, melanomas, systemic lymphomas, etc.)
Brain tumors
Why do they produce clinical sx
Most brain tumors produce clinical symptoms because of mass effect (increased ICP, headache, papilledema), local damage to particular brain structures (focal neurologic deficits), or seizures (usually from damage to cerebral cortex).
Primary brain tumors
Benign or malignant
Primary CNS tumors rarely metastasize outside the CNS and then usually only after surgical biopsy or resection, presumably due to disruption of normal anatomic barriers.
Some tumors (e.g., some gliomas, medulloblastoma), however, can disseminate within CSF pathways causing damage to cranial and spinal nerve roots, blockage of CSF flow with hydrocephalus, etc., despite being relatively low-grade under the microscope.
Prognosis is frequently more related to location and resectability than to histologic type or grade of tumor: e.g., pilocytic astrocytoma (WHO grade 1) located in the optic nerve or hypothalamus may be devastating but in the cerebellum amenable to curative resection.
Primary brain tumors
classification
The terms “benign” and “malignant” are, thus, best avoided, except for certain primary tumors (e.g., primary CNS lymphoma) and metastases to the brain, which are, by definition, malignant. Tumors are, however, graded based on their histologic appearance: low grade = WHO grades 1-2 (usually implies relatively good long-term prognosis); high grade = WHO grades 3-4 (indicates likelihood of rapid growth and poor long-term prognosis). Staging criteria exist but are less utilized than for tumors in other organs.
Gliomas
Types
list
Astrocytomas
Oligodendroglioma
Ependymomas
Choroid plexus tumors
Most common primary brain tumor
Astrocytoma
Diffuse astrocytoma
Gen chars
these characteristically infiltrate the brain (cerebrum in adults, brainstem in children) and show a spectrum of anaplasia with a correspondingly aggressive clinical course.
astrocytoma (WHO grade 2) anaplastic astrocytoma (WHO grade 3)
glioblastoma (AKA glioblastoma multiforme) (WHO grade 4).
Diffuse astrocytoma
Grade vs age
Lower-grade tumors tend to occur in younger to middle-aged adults, and older adults generally have higher-grade tumors at initial diagnosis.
Diffuse astrocytoma
Glioblastoma
Char features
The highest-grade tumor (glioblastoma) typically shows areas of proliferation of microvessels (producing contrast enhancement on imaging studies) and necrosis.
Diffuse astrocytoma
Median survival
Median survivals from diagnosis approximate 5 years for astrocytoma, 2 years for anaplastic astrocytoma, and less than 1 year for glioblastoma. When tumors recur, they have often progressed to a higher grade with correspondingly shortened survival.
Pilocytic astrocytoma
Gen chars
Pilocytic astrocytoma (WHO grade 1): characteristically occurs in children or young adults, usually in the cerebellum, optic nerve, or spinal cord, and usually has an indolent course. Formation of macroscopic cysts and microscopic accumulations of alphaBcrystallin protein in tumor cells (Rosenthal fibers) are common. Tumors only rarely progress to a higher grade at recurrence.
Oligodendroglioma
chars
Oligodendroglioma (WHO grade 2) and anaplastic oligodendroglioma (WHO grade 3): these usually occur in the cerebrum of younger adults, show infiltrative growth, often cause seizures, and may contain calcifications. Median survival approaches 10 years for grade 2 tumors
Ependymomas
chars
Ependymomas (grade 1 or grade 2) grow as solid tumors, typically in the ventricles or central canal of the spinal cord, may cause obstructive hydrocephalus, and may form microscopic structures resembling mini- ventricles (true ependymal rosettes). Anaplastic ependymoma (grade 3) usually occurs in children. Prognosis varies by subtype and grade, but ependymomas in children often have poor long-term outcomes.
Choroid plexus tumors
Gen chars
Choroid plexus tumors (choroid plexus papilloma, WHO grade 1, or choroid plexus carcinoma, WHO grade 3) also occur within the ventricles and may cause obstructive hydrocephalus or overproduction of CSF.
Primitive neuroectodermal tumors (PNET)
Gen chars
Tumors resembling embryonic brain cells most commonly occur in children, are highly aggressive tumors, and may occur in the setting of particular tumor syndromes.
