NP3E Flashcards
Tumors can arise from cells in the nervous system
primary tumors
Tumors can spread to the nervous system via the blood supply or by direct extension
secondary tumors
Is the process whereby a normal cell acquires the capacity for autonomous growth. The resultant neoplastic cell is no longer sensitive to growth inhibitory influences within its environment.
Carcinogenesis
Carcinogenesis occurs in a series of steps:
Initiation
Promotion
Progression
Alteration of the genetic information of a cell occurs, being fixed by a round of replication
Initiation
The genetic alteration is ultimately expressed as unique cellular characteristics (phenotype) following additional rounds of replication. For certain of these cells, the new phenotype confers a selective advantage to survival over its neighbors and we call this the resistance phenotype. Additional alterations to the genetic information may occur during this time, each fixed by a round of replication. As a result, mature neoplasms have multiple mutations, which is why the initial causative change can be so hard to pin down.
Promotion
Further replication in an environment otherwise inhibitory to autonomous growth drives a survival of the fittest evolutionary process for the altered cells. A neoplastic cell is a result.
Progression
In general, approximately ______ of tumors are primary – secondary tumors are common
50%
___________ tumors are common.
meningeal
Other mesenchymal tumors such as lymphoma can be a _____________ although careful examination of other tissues must be performed to rule out the involvement of other organ systems
primary tumor
_________ tumors are less common, but they do occur
Glial
Why don’t tumors arise from differentiated neurons?
because neuronal differentiation is terminal
Tumors can arise from undifferentiated stem cells in the _______
young
a group of tumors defined by their appearance and are thought to develop from primitive (undeveloped) nerve cells in the brain
Primitive Neuroectodermal Tumors (PNET)
In a cat with an intracranial tumor, greater than ______will be primary and _____ of those will be meningiomas
70%, 58%
If a tumor looks like it’s composed of astrocytes, then we assume it is derived from the astrocytic lineage
astrocytoma
If it looks like it is arising from the meninges, it’s likely a _____________
meningioma
If it is arising from the parenchyma, it is likely an ______________ or __________
oligodendroglioma or astrocytoma
If it is arising from the lining of a ventricle, it may be either a ___________ or an ___________
choroid plexus tumor, ependymoma
A tumor in the posterior fossa of a young animal might be a __________
PNET
If there are multiple masses, then it is likely a ______________
secondary tumor
A ______________ should be a differential for a single mass
granuloma
Differentials for multiple masses would be ______________or _______________
secondary tumors, granulomatous inflammation
Tumors of _________ or the ________ can involve the nervous system by direct extension
bone, pituitary
_________tumors in other organ systems are well differentiated, sharply demarcated from adjacent tissues, and may even be encapsulated by fibrous connective tissue
Benign
___________ tumors are less well differentiated, exhibit atypical cell morphologies, and may spread by direct extension (infiltrative growth) or metastasis
Malignant
In the ______________, any rapidly growing tumor is considered to be “malignant” because of the consequences of rapid growth
nervous system
histological criteria differ to a degree, in that slowly growing “benign” _________tumors are never encapsulated and may exhibit infiltrative growth along their perimeter
glial
Indicators of aggressive biological behavior in nervous system tumors:
- lack of differentiation
- atypia
- evidence of rapid growth
- metastasis
Cells with variability in nuclear size and shape, multinucleated cells, and mitotic figures that represent cells that get stuck in variable stages of cell division
atypia
Vascular proliferation (to feed the tumor), necrosis (where the tumor outgrew its blood supply) and a high mitotic index
evidence of rapid growth
Tumors growing into the ventricles may shed neoplastic cells and spread throughout the ventricular system. This is seen with choroid plexus tumors and oligodendrogliomas.
metastasis
Indicators of more aggressive biological behavior are reflected in the diagnosis. A tumor of astrocytic origin would be considered a high grade or anaplastic ____________. In the extreme, it would be called a __________
astrocytoma, glioblastoma
A ____________ tumor can be clinically silent or unnoticeable for months or years. It is when the tumor triggers a response such as an edema cycle that clinical signs become overt
nervous system
ischemic necrosis of grey matter, herniation and death
The edema cycle
Hydrocephalus for a tumor that obstructs ______ flow
CSF
