Brain Cancer: Overview

What Is It?

Epidemiology

• ~93,000 new brain/CNS tumor diagnoses are projected in the US in 2025, including both benign and malignant types (National Brain Tumor Society, 2025).
• Of these, ~26,000 are malignant primary CNS tumors per year.
• Malignant incidence rate: ~9 per 100,000 person-years in adults over 40.
• Childhood rate: ~5.5 per 100,000 - pediatric brain tumors are the #1 childhood cancer by mortality.
• Incidence rises sharply after age 55.
• A slight male predominance exists for malignant tumors (7.5 vs. 5.4 per 100,000). However, when benign tumors are included, women have a higher overall rate, largely due to the female predominance of meningiomas.
• Race: White individuals have higher incidence rates than Black individuals (8.5 vs. 4.8 per 100,000 in males).
• 5-year survival: Overall ~35% for malignant primary brain tumors - the sixth lowest among all cancers. Varies dramatically by subtype (see below).
• Bradley and Daroff's Neurology in Clinical Practice, Ch. 71

Major Types

1. Primary Brain Tumors

Gliomas (most common malignant primary brain tumor)

Meningioma (most common primary brain tumor overall, ~35%)

• Arises from the dura mater (meningothelial/arachnoidal cap cells).
• More common in women and with increasing age.
• WHO grades I (benign) to III (malignant).
• Many found incidentally on imaging. Small, asymptomatic ones can be monitored; larger ones are resected.
• Associated with NF2 and prior cranial radiation.

Schwannoma (~9% of primary brain tumors)

• Arises from Schwann cells of cranial nerve roots.
• Most common: vestibular schwannoma (acoustic neuroma), from cranial nerve VIII.
• Generally benign; bilateral in NF2.

Medulloblastoma

• Most common malignant childhood brain tumor.
• Arises in the cerebellum (posterior fossa).
• Associated with Gorlin syndrome and Li-Fraumeni syndrome.

Pituitary Adenoma

• Common, often benign.
• May be functional (e.g., prolactinoma causing amenorrhea/galactorrhea) or non-functional.

2. Metastatic Brain Tumors (Secondary)

• More common than primary malignant brain tumors.
• Most frequent sources: lung, breast, melanoma, kidney, colon.
• Typically multiple lesions; enhance with gadolinium on MRI.
• Serum tumor markers (e.g., beta-hCG for testicular cancer) may be elevated.

Symptoms

• Headache - often worse in the morning, may worsen with exertion or position change
• Nausea and vomiting (vomiting preceding headache by weeks is characteristic of posterior fossa tumors)
• Cognitive difficulties, personality change, apathy
• Gait disorder

• Hemiparesis (weakness on one side)
• Aphasia (language difficulty, often mistaken for confusion)
• Visual field defects
• Seizures - occur in ~25% of patients with malignant gliomas or brain metastases; in up to 90% of low-grade glioma patients as the presenting symptom. All brain tumor seizures have a focal onset.

Imaging (Diagnosis)

• Malignant tumors (primary or metastatic): typically enhance with gadolinium, show central necrosis, and are surrounded by white matter edema.
• Low-grade gliomas: do NOT typically enhance; best seen on FLAIR sequences.
• Meningiomas: extra-axial, densely enhancing, with a characteristic dural tail.

Hereditary / Genetic Risk Syndromes

Prognosis by Subtype