Tumors & Cysts

Astrocytomas

• Pilocytic astrocytoma (PA)

  • A slow-growing tumor composed of astrocytes, usually found in children. It can also be seen in patients with tuberous sclerosis, NF1, and Li-Fraumeni syndrome.
    • Optic nerve and chiasm glioma are associated with NF1.
  • Often presents with symptoms of increased ICP (headache, nausea/vomiting), vision loss, ataxia, or cranial nerve deficits depending on location.
  • Imaging: Cystic mass with a contrast rim-enhancing nidus or mural nodule with minimal vasogenic edema, dorsally exophytic. Most commonly found in the cerebellum > supratentorial hemispheres > optic pathway/hypothalamus > spinal cord.

    

  • KIAA1549-BRAF gene fusion is characteristic of this tumor type.
  • Pathology: Hair-like cytoplasmic fibers (Rosenthal fibers) and eosinophilic granular bodies in stacked bipolar cells.

    

  • 90% 10-year overall survival. It can be treated with surgical resection alone, and rarely progresses to malignant glioma.
  • Classic patient presentation: child presenting with increased ICP/ataxia found to have a cerebellar cystic mass lesion with enhancing mural nodule.

• Subependymal giant cell astrocytoma (SGCA or SEGA)

  • Almost exclusively seen in pediatric patients with tuberous sclerosis.
  • Often asymptomatic, but when symptomatic presents with obstructive hydrocephalus due to location in the foramen of Monro.
  • Imaging: Well circumscribed, partially-calcified intraventricular contrast-enhancing mass near the foramen of Monro.

    

  • Pathology: Large polygonal cells with eosinophilic cytoplasm and a smaller number of giant pyramidal ganglioid astrocytes.

    

  • Often curative with surgical resection.
  • Tuberous Sclerosis Review: classically presents with seizures, mental retardation, and adenoma sebaceum. Associated with TSC2/tuberin (most cases) or TSC1/hamartin with cortical or subependymal tubers, hamartomas, renal angiomyolipomas, and cardiac rhabdomyomas.

• Pleomorphic xanthoastrocytoma (PXA)

  • Found in young patients who present with temporal lobe epilepsy.
  • Imaging: Supratentorial peripheral cystic and contrast-enhancing mass abutting the leptomeninges with enhancing dural tail sign and scalloping of overlying bone.
  • Pathology: variable histological features (thus, pleomorphic) with spindle cells, polygonal cells, multinucleated cells, highly variable nuclear size, and astrocytes with eosinophilic granular bodies.
  • Associated with BRAF mutations (similar to pilocytic astrocytomas).
  • Treated with surgical resection, but local recurrence and malignant transformation are common.

• Diffuse astrocytoma

  • Young adults 20-45 often present with seizures and headaches
  • Diffuse infiltrating tumor, synonymous with fibrillary astrocytoma
  • Associated with isocitrate dehydrogenase (IDH), TP53, and ATRX gene mutations.
    • Gemistocytic astrocytoma is a subtype of IDH mutant diffuse astrocytomas with more aggressive behavior.
  • Imaging: T2 hyperintense infiltrating mass lesion with ill-defined borders, non-contrast enhancing; MRS with elevated choline peak, low NAA peak, elevated choline: creatine ratio
  • Treatment: maximal safe resection, involving field radiation followed by chemotherapy.

• Anaplastic astrocytoma (AA)

  • Better prognosis if it is associated with IDH1/2 mutation and MGMT methylation.
    • IDH wild-type tumors exhibit more aggressive behavior.
  • Imaging: An infiltrating mass that predominantly involves hemispheric white matter with variable enhancement.
    

    

    
  • Pathology: Increased cellularity, marked mitotic activity, and distinct nuclear atypia. No necrosis or endothelial proliferation is present.

• Glioblastoma multiforme (GBM)

  • Imaging: Contrast-enhancing multicystic lesions with significant vasogenic edema. Lesions can also have internal necrosis and can extend through the corpus callosum. Often called the “butterfly lesion.”

• Genetics:
  • MGMT promoter methylation confers a better response to alkylating chemotherapy.
  • IDH-1/2 mutations are associated with secondary GBM arising from a lower-grade glioma.
• Pathology: Cells with increased mitotic activity with pseudopalisading necrosis and microvascular endothelial proliferation.

• Treatment: Maximal safe resection followed by intensity-modulated radiation therapy (IMRT) plus concomitant temozolomide (alkylating chemotherapy) followed by adjuvant temozolomide.
  • Methylation of the MGMT gene is associated with better treatment response to temozolomide.
  • Bevacizumab, a monoclonal antibody that inhibits vascular endothelial growth factor (VEGF)  can be used in recurrent or progressive GBM.