CNS Flashcards
Epidemiology of CNS tumors?
Primary tumors are extremely rare tumors. Among all tumors 75% are metastases. CNS tumors can have different clinical courses depending on exact location and size. Classified by WHO, grade I and II are benign, grade III and IV are malignant. Furthermore divided in midline brain structures, mid saggital structures, subtentorial regions and base of skull. Finally they can be tumors of neuroepithelial tissue, of meninges, lymphoma or germ cell tumors.
What is an Astrocytoma?
Astrocytomas are the most frequent tumors among primitive CNS tumors, seen in patients of any age (>10 y.o). Astrocytomas may range from grade I to grade IV: usually grade I - grade II tumors. found anywhere from the cerebral hemisphere to the spinal cord. They most commonly occur in between the 4th and 6th decade. Usually arise with seizures, headache and focal neurological deficits. Clinical features depend on the location and growth rate of the tumor.
What is a pilocytic astrocytoma?
Pilocytic astrocytoma is a grade I glioma. It is a well demarcated, relatively benign tumor, slow growing kind of tumor, often cystic and well circumscribed, not infiltrative. It occurs in children and young adults, frequently in the cerebellum, even though it may also affect other sites. The tumor is composed of bipolar cells with thin processes that from a dense fibrillary meshwork. It is very cellular tumor, and also well vascularized which is an exceptional feature for its being low grade.
What is a pleomorphic xanthoastrocytoma?
It is a grade II tumor, that occurs most often in the temporal lobe of young adults, usually with a history of seizures. It has a good 5/y survival (80%) as it can be completely resected. Pleomorphic xanthoastocytoma are usually solid lesions, with some cystic or calcific regions that can be easily recognized at imaging. The term “pleomorphic” indicates a type of tumor with bizarre, differently- shape cells. The term “xantho”, instead, underlines that it is a lipid-related tumor. It is characterized by very large cells full of lipid droplets. The tumor is characterized by high nuclear atypia, abundant reticulin deposits, relative circumscription and chronic inflammatory cell infiltrates, in the absence of necrosis and high mitotic activity.
What is a diffuse astrocytoma?
Grade II. They are poorly defined, gray, infiltrative tumors that expand and distort the invaded brain. The tumor may appear well demarcated from the surrounding tissue on imaging, but infiltration beyond the outer margin is always present. Microscopically, there is a variable degree of nuclear polymorphism and the transition between neoplastic and normal tissue.
What is an anaplastic Astrocytoma?
Grade III. Anaplastic astrocytomas are characterized by higher cell density, and greater nuclear polymorphism, with the presence of many mitotic figures. This is a very aggressive, rapidly evolving tumor characterized by a high positivity to Ki67. Vascularization is also present.
What is a glioblastoma multiforme?
The highest grade is defined by glioblastoma (grade IV). It is the most common and most lethal primary brain tumor. It is highly resistant to both RT and CT and, despite therapy, it shows high recurrence and progression. There are very few examples of survival after two years (OS ~ 14 months): indeed, incidence almost corresponds to the mortality, which is around 95%. At histological analysis it is similar to anaplastic astrocytoma, with a high mitotic activity and vascularity. Indeed, differential diagnosis is based on presence of massive necrosis.
Note that vessels are leaky, predisposing the lesion to hemorrhage. Another peculiarity is pseudo palisading necrosis which is caused by atypical tumoral cells are all concentrated outside the central necrotic area, forming a sort of ring around the clotted portion. GBM contains the largest and most abdominal cells in pathology. GBM may arise de novo or evolve from pre-existing lower grade astrocytoma/oligodendroglioma.
What are Oligodendrogliomas?
Oligodendrogliomas are the second most common type of glial tumors and are classified in two grades: oligodendrogliomas (grade II) and anaplastic oligodendrogliomas (grade III). Oligodendrogliomas can progress to GBM. Oligodendrogliomas account for 5-15% of gliomas and are very slowly progressing tumors, which arise in the 4-5th decade of life. They mostly occur in cerebral hemispheres, with predilection for white matter. They are are well circumscribed, gelatinous, gray masses, often with cysts, focal hemorrhages and calcification. The morphology of cells is quite typical : fried egg cells. They resemble healthy oligodendrocytes with high cellular density. Vascularization is generally normal and there is a low proliferative activity.
What are ependymomas?
Ependymomas arise from the ependyma, next to the ependyma-lined ventricular system. Ependymomas are solid well demarcated masses. Those in the posterior fossa are not reachable by surgery, while intraspinal tumors are easily removed. These tumors show a specific organization of neoplastic cells with cytoplasmic processes anchoring them to surrounding vessel walls.
A non neoplastic DDX of ependymoma is Colloid cyst of the third ventricle.
