Tumors and cysts are a large portion of the board RITE® exams and a moderate portion of Shelf exams. In this chapter, you will review high-yield neurologic cancers and cysts, and find many high yield images and pathology. You should be able to quickly recognize each of the images on this page! Test your knowledge with our question bank and flashcards!

Authors: Megan Mantica MD, Brian Hanrahan MD

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Tumors of Neuroepithelial Tissue

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.
      Pilocytic Astrocytoma
      Pilocytic Astrocytoma
    • 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.
      Rosenthal Fibers of Pilocytic Astrocytoma
      H&E stain, Pilocytic astrocytoma showing both compact (left) and microcystic (right) regions.  Brightly eosinophilic bodies called Rosenthal fibers are also present (arrow).
    • 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.
      Subependymal Giant Cell Astrocytoma
      Subependymal Giant Cell Astrocytoma
    • Pathology: Large polygonal cells with eosinophilic cytoplasm and a smaller number of giant pyramidal ganglioid astrocytes.
      Subependymal Giant Cell Astrocytoma
      GFAP, NeuN, S100 stains showing clusters of polygonal cells with abundant glassy cytoplasm and eccentric nuclei with prominent nucleoli. Giant cells and multinucleated cells are present and embedded in a fibrillary background with focal perivascular pseudopalisades consistent with subependymal giant cell astrocytoma.
    • 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 presenting with seizure 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, involved 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 better response to alkylating chemotherapy.
    • IDH-1/2 mutations 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 a better treatment response to temozolomide.
    • Bevacizumab, monoclonal antibody  which inhibits vascular endothelial growth factor (VEGF)  can be used in recurrent or progressive GBM.

Oligodendrogliomas

  • WHO grade II or WHO grade III (anaplastic oligodendrogliomas)
  • Associated with 1p/19q co-deletion and IDH mutations;
    • 1p/19q co-deletion patients have an better overall prognosis compared to astrocytic tumors which are 1p/19q normal.
  • Imaging: Partially calcified T2 heterogeneous, hyperintense subcortical/cortical masses (most often frontal or temporal lobes); typically non-contrast enhancing.
  • Commonly occurs in the 4thor 5thdecade of life.
  • Pathology: Cells with a “fried egg” appearance with monotonous round nuclei, surrounded by prominent perinuclear halos.



 

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