Tumors of the CNS Flashcards
Describe diffuse astrocytomas grossly and microscopically. What grade is it? How often does it progress?
- Invade the cerebrum diffusely producing distortion and expansion of normal tissue
- Cells have elongated, irregular hyperchromatic nuclei embedded in a meshwork of fibrillary processes
- Grade II tumor–no mitoses are present (low grade)
- 75% of grade II tumors progress to grade IV
Describe anaplastic astrocytomas.
More aggressive grade III tumors which almost always progress. Mitotic figures are present and distinguish it from diffuse astrocytomas.
Describe the microscopic and gross characteristics of glioblastomas. What process is exhibited in the image?Where do GBMs arise from? How do genetics relate to this?
- Gross: can have necrotic, hemorrhagic masses which can cause herniation
- Microscopic: foci of necrosis, neovascularization (image), formation of glomeruloid tufts
- Arise de novo: primarily overexpress EGFR
- Secondary from grade II astrocytoma: primarily mutations in TP53 or IDH1/2
What types of non-infiltrating or circumscribed astrocytomas exist? What grade are they?
All are grade I/II
Pilocytic astrocytoma:
- Occur mainly in children often in the cerebellum
- Rarely progress and do not infiltrate
- Genetics: gains on 7q34 resulting in tandem duplication between BRAF and KIAA1549 creating oncogene fusion protein
- Architecture: Rosenthal fibers among fascicle of spindle shaped eosinophilic granular bodies in cystic areas
- No necrosis and no mitotic figures
Other types:
- Pleomorphic xanthoastrocytoma
- Subependymal giant cell astrocytoma: typically present in tuerous sclerosis
What type of CNS tumor is exhibited below? What grades of these tumors exist? Describe their gross, histological, and genetic features.
Oligodendrogliomas exist as a grade II well-differentiated, infiltrating tumor. Malignant, analastic grade III variant exists as well (no grade IV).
- Often expands into gyri and white matter (infiltrative)
- Microscopically, small centrally located nuclus surrounded by scant cytoplasm (fried egg) and vessel branching (chicken-wire)
- Loss of heterozygosity for chromosomes 1p and 19p are seen in 80% of cases and this is a favorable prognositic factor
What types of CNS tumor is pictured below? What grades of this type of tumor exist? Describe its histological features.
Ependymomas are grade II but can have an anaplastic grade III variant when mitoses and necrosis becomes evident (no grade IV)
- Neoplastic cells tend to cluster around blood vessels producing pseudorosettes
- Rosettes and canals are found in a minority of ependymomas
What type of embryonal tumor is pictured below? What grade is it? Describe its features and pattern of spread.
Medulloblastoma: grade IV highly proliferative tumor
- Pleomorphic: cystic areas, solid areas, areas of hemorrhage, necrosis
- Well circumscribed but can infiltrate and has a tendency to spread throughout the subarachnoid space via CSF
- Originates from granule neuron precursor cells that produce external granule layer of cerebellum
- Densely packed cells with round ovoid nuclei, frequent mitosis, and neuroblastic rosettes (sign of neuronal differentiation)
- Requires very intense treatment–surgical, radiation, and chemotherapy
What types of tumors arise from cranial and spinal nerves? Describe their features.
- Schwannomas: slow growing neoplasm of Schwann cells, often involving CN VIII and can be bilateral. Most are benign and can be resected. Can be associated with NF2.
- Neurofibromas: may be dermal (nodular lesion), intraneural, solitary, or plexiform. They are grade I but difficult to deal with because it is in the nerve roots. Can be associated with NF1.
- Peripheral nerve sheath tumors
What kinds of meningiomas exist? Where do they arise? What disease are they associated with?
Arise from meningothelial cells of the leptomeninges and can present in all different areas of the meninges. They are grade I but ease of resection depends on its location.
- Transitional meningioma: whorls and cords of neoplastic cells
- Psammomatous meningioma: consists of numerous compact whorls that contain psammoma bodies
- Fibrous meningiomas
Describe metastatic tumors and how they present on MRI. How are they treated?
Secondary CNS neoplasms result from metastases in adults often from lung, breast, skin, kidney, and colon. They present as multiple ring enhancing lesions on MRI and can be resected if there are only a few, otherwise chemotherapy and radiation are used.
Describe the incidence of primary CNS tumors as they pertain to age and gender.
Primary CNS tumors account for 2% of all malignant neoplasms
- Age distribution is bimodal: peaks in children under 5 and then again in adults 45-70 years of age
- Children: CNS tumors account for 20% of childhood cancer, specifically pilocytic astrocytoma and medulloblastoma
- Adults: primary CNS tumors are most often meningiomas and glioblastomas
- Males: gliomas and embryonal tumors are more common
- Females: meningiomas are more common
Describe the etiology of primary CNS tumors.
Most are of unknown etiology, fewer than 5% are associated with hereditary predisposition.
- Neurofibromatosis type 1: neurofibromas, malignant nerve sheath tumor, optic nerve astrocytoma, and meningiomas
- Neurofibromatosis type 2: schwannomas, meningiomas, ependymomas
- Tuberous sclerosis: subependymal giant cell astrocytoma
- Li-Fraumeni syndrome: gliomas
- Von Hippel-Lindau syndrome
- Gorlin syndrome
What environmental risk factors exist for primary brain tumors?
High dose ionizing radiation (specifically associated with meningiomas)
Who is at risk for CNS lymphomas?
CNS lymphomas are associated with congenital or acquired immunodeficiency. Patients at risk:
- Organ transplant immunosuppression
- Hematologic malignancies
- AIDS
- Autoimmune disease
What types of symptoms can CNS tumors present with?
Location based symptoms:
- Focal or generalized epilepsy
- Focal neurological deficits
- Mental changes
- Obstructive hydrocephalus
Symptoms related to increased intracranial pressure:
- Headache
- Vomiting
- Papilledema
- Clouding of consciousness or coma
- Brain herniation
