CNS Neoplasm I & II

Question 1

WHO Grade I lesions characteristics

Answer 1

• tumors with low proliferative potential and high possibility of cure following surgical resection alone
• Well demarcated, surgically excisable.

Question 2

WHO Grade I lesion example

Answer 2

• Example: pilocytic astrocytoma
• occurs @ childhood
• @ cerebellar hemispheres, optic nerves and chiasm, and hypothalamic region.
• Gross total resection possible @ cerebellar lesion
• gross total resection impossible @ optic chiasm or hypothalamus

Question 3

WHO Grade II lesion characteristics

Answer 3

• generally infiltrative
• low level proliferative (ie., mitotic) activity,
• often recur.
• Some grade II tumors tend to progress to a higher grade of malignancy

Question 4

WHO Grade II lesion example

Answer 4

• Example: diffuse astrocytoma.
  
  • Hits adults age 30-50, has ill-defined borders, not surgically resectable
• Progression examples: low-grade diffuse astrocytomas (WHO grade II) ==> anaplastic astrocytoma (WHO grade III) or glioblastoma (WHO grade IV) over a few years time.
  
  • Similar transformation to higher grade tumor occurs also in oligodendrogliomas and mixed (oligoastrocytomas) gliomas.

Question 5

WHO Grade II treatment

Answer 5

• watchful waiting (ie., close-interval neuroimaging scans to detect upgrading)
• external beam cranial irradiation, depending on location, clinical features, type and size of lesion.

Question 6

WHO Grade III lesion characteristics & example

Answer 6

• lesions with histological evidence of malignancy, including nuclear atypia and brisk mitotic activity.
• patients with Grade III tumors receive adjuvant radiation and/or chemotherapy.
• Example: anaplastic astrocytoma: more nuclear atypia

Question 7

WHO Grade IV lesion characteristics

Answer 7

• cytologically malignant, mitotically active, necrosis-prone neoplasms
• often associated with rapid pre and post operative disease evolution and fatal outcome.
• Common examples of Grade IV neoplasms include glioblastoma and medulloblastoma.

Question 8

Glioblastoma characteristics

Answer 8

• WHO Grade IV lesion
• Highly infiltrative, often hemorrhagic neoplasm that is necrotic at the microscopic and sometimes gross level.
• Dismal prognosis. More than 90% of GBMs are primary, only 2-4 months of symptoms.
• Has a bright rim and necrotic center on CT scan.
• Necrotic center releases HIF and VEGF which causes blood vessels to start developing again and vascularizes the rest of the tumor.
• Secondary GBM: progression from lower grade tumor, younger age (<45), longer duration of symptoms

Question 9

General treatment approaches for WHO grade I - IV tumors

Answer 9

1: cut it out and it’s ok
2: can’t resect, will often upgrade to grade 3 or 4. Treat with radiation and close observation
3: chemo + radiation
4: rapid growth, fatal, adjuvant therapy has little data supporting use

Tempo parallels grade: Grade 1 grows slowly, grade 4 grows quickly

Question 10

Histologic typing/grading and prognosis

Answer 10

• Grading: look at the tumor in microscope and decide how aggressive it will behave (mitotic figures, vascularity and necrosis, invasion).
• Tells you how you will have to treat it and how fast it will kill.

Question 11

Tumor types that tend to spread throughout CSF axis

Answer 11

• Astrocytomas and oligodendrogliomas DO NOT ==> into the CSF pathway and disseminate through the cerebrospinal fluid.
• DOES occur late in the course of some ependymomas, especially those in childhood and originating in the 4th ventricle, and especially in medulloblastomas.