Clinical - Tumours of the CNS Flashcards
CNS tumours require an integrated diagnosis. What 3 aspects does this include?
- Histology
- WHO - Grade
- Genetic
What % of lung cancers spread to the brain?
20%
What is a glioma?
Glioma is a type of tumor that begins in the glial (supportive) cells that surround nerve cells and help them function.
What is a meningioma?
A meningioma is a tumor that forms on membranes that cover the brain and spinal cord just inside the skull (meninges)
What is a blastoma?
A blastoma is a type of cancer caused by malignancies in precursor cells, which are commonly referred to as blasts
What is a medulloblastoma?
Medulloblastoma is the most common type of cancerous brain tumor in children - most commonly starts in the cerebellum.
There are 4 major types of glial cells in the CNS?
- Astrocytes
- Oligodendrocytes
- Ependymal cells and choroid plexus cells
- Microglia
Function of astrocytes?
- Support and protection
- Bridge blood to the neurones, providing nutrition
- Also metabolise the nutrients so that they are suitable for the neurones.
Function of oligodendrocytes?
myelin production
Function of microglia?
- As the resident macrophage cells, they act as the first and main form of active immune defense in the central nervous system (CNS).
- Come from mesoderm
What are ependymal cells?
The cell type lining the brain ventricles. As non-neuronal cells in the brain and derived from neuroectoderm, they are clearly defined as a subtype of glial cells.
Function of ependymal cells and choroid plexus cells?
Produce CSF
What is the GFAP stain in histology? What is it useful for?
- Done to determine whether cells contain glial fibrillary acidic protein, a protein secreted by a normal astrocyte
- It is useful for determining whether a tumour is of glial origin
Histology of CNS tumours. What is the criteria?
- mitosis: for cell division
- vascular endothelial proliferation: more blood vessels to supply growing tumour
- necrosis: tumour necrosis factor secreted by tumour to remove competition, kill the environment
-
dedifferentiation: Cell dedifferentiation is the process by which cells grow reversely from a partially or terminally differentiated stage to a less differentiated stage
- loss of functional brain cells to promote growth
CNS tumours can be graded 1-4 (WHO). Describe each grade
- 1: benign, no recurrence, no/very slow progression
- 2: low grade, progression to 3 (astrocytoma 6-7year)
- 3: high grade, rapid progression (astrocytoma 2-3years)
- 4: aggressive
Molecular genetic ring:
- Inner ring –> driver of mutation
- IDH is the most common, leading to uncontrolled cell division
- Middle ring –> additional mutations
- With time, additional mutations in the middle ring will occur. These affect the survival of the cell e.g. EGFR
- Outer ring –> histological diagnosis
- Determines the prognosis
- H3G34R with ATRX and GBM lead to poor prognosis, for example
What are Schwann cells?
Schwann cells are a type of glial cells of the peripheral nervous system that help form the myelin sheath around the nerve fibers.