Background

Question 1

What % of primary CNS tumors are malignant?

Answer 1

∼35% of primary brain tumors are considered malignant.

Question 2

In adults, what is the most common malignant CNS neoplasm?

Answer 2

∼80% of CNS neoplasms in adults are glioblastoma (GBM), which constitutes 20% of all primary tumors. ∼26,000 new malignant primary brain tumors are diagnosed annually in the United States.

Question 3

What are the WHO classifications for high-grade CNS tumors?

Answer 3

WHO III: anaplastic astrocytoma (AA)/anaplastic oligodendroglioma (AO)/anaplastic oligoastrocytoma (AOA)

WHO IV: GBM

Question 4

What are some common genetic changes seen in malignant brain tumors?

Answer 4

↑ EGFR (50%) and phosphatase and tensin homolog (PTEN) mutation (30%–40%)

Question 5

What are the initial genetic changes associated with primary vs. secondary GBM?

Answer 5

Primary: ↑ EGFR/MDM2 amplification/LOH 10/p16 loss

Secondary: p53 mutation → LGG → LOH 19q/p16 loss → AA → LOH 10, DCC → 2nd GBM; IDH mutation is also very common in secondary GBM

Question 6

What % of GBMs are multicentric?

Answer 6

<5% of GBMs are multicentric.

Question 7

What are the 4 pathologic characteristics used for astrocytoma grading?

Answer 7

Nuclear Atypia, Mitoses, Endothelial proliferation, and Necrosis

(Mnemonic: AMEN)

Question 8

What is the defining pathologic characteristic of GBM?

Answer 8

Necrosis