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Anaplastic Astrocytoma (AA)

Last Updated: August 23, 2020

Open Table of Contents: Anaplastic Astrocytoma (AA)

Figure 1: (Top Left) Axial FLAIR demonstrates a left insular infiltrative lesion involving the cortex and white matter. This anaplastic astrocytoma is fairly circumscribed, a less common characteristic in these higher grade lesions. (Top Right) ADC demonstrates no appreciable dark restricted diffusion in this lesion to suggest hypercellularity. (Bottom) Axial T1WI postcontrast shows a small round area of enhancement in the superficial insula, a feature more typical of higher grade glioma. If the T2/FLAIR hyperintensity surrounding this lesion spared the cortex, the enhancing lesion may be more easily mistaken for metastasis with surrounding vasogenic edema.

Figure 2: The medial left frontoparietal complex-appearing anaplastic astrocytoma in this patient demonstrates low T1 signal intensity (top left) and FLAIR hyperintensity (top right) with a mixed-signal hemorrhagic component at its posterolateral aspect. Black signal on the susceptibility-weighted imaging (middle left) also reflect this hemorrhage. The tumor also has a heterogeneous enhancement pattern (middle right, coronal; bottom row, sagittal) that is more typical of higher-grade adult primary brain tumors than of grade II tumors.

BASIC DESCRIPTION

  • Infiltrating malignant astrocytoma with ill-defined tumor margins and extensive edema

PATHOLOGY

  • WHO grade III
  • Usually develops from malignant degeneration of low-grade astrocytoma (WHO grade II)
  • Commonly dedifferentiates into GBM (~50%) within 2 years
  • Focal or diffuse anaplasia, highly proliferative
  • Increased cellularity and nuclear atypia; usually no necrosis or microvascular proliferation

CLINICAL FEATURES

All ages affected (fourth and fifth decades of life most common)

  • Slight male gender predilection
  • Median survival 2–3 years
    • Better prognosis with younger age, gross total resection, absence of enhancement, KI-67 index ≤5.1%, and IDH1- or MGMT-positive genetics
  • Presenting symptoms dependent on tumor location

    • Seizures, headaches, behavioral changes, clinical deterioration in patients with known low-grade astrocytoma
  • Treatment: resection, chemotherapy (temozolomide), radiation

IMAGING

  • General
    • Ill-defined, infiltrating white matter mass
      • Location in frontal and temporal lobes most common; brainstem and spinal cord uncommon
      • Infiltrates beyond apparent imaging tumor margins
      • Expansion and involvement of adjacent cortex common
    • Variable enhancement

      • Usually nonenhancing, but patchy or nodular enhancement may be present
    • Cysts and hemorrhage are uncommon features
    • Spreads along white matter tracts, but may spread via cerebrospinal fluid (CSF), leptomeninges, and ependyma
  • CT

    • Hypodense, ill-defined white matter mass
    • Hemorrhage and calcification uncommon features
    • Usually does not enhance on contrast-enhanced CT, but may show focal or patchy enhancement
      • Ring enhancement suggests progression to GBM
  • MRI

    • T1WI: isointense to hypointense
    • T2WI: heterogeneously hyperintense; presence of flow voids suggests vascular proliferation and progression to GBM
    • FLAIR: heterogeneously hyperintense
    • DWI: usually no diffusion restriction
    • T1WI+C: usually no enhancement; may show patchy or nodular enhancement
    • MRS/MR perfusion: decreased NAA, increased Cho/Cr ratio, increased relative cerebral blood volume (rCBV) compared with low-grade astrocytomas, although usually less than glioblastomas
    • Diffusion tensor imaging (DTI) may assist in surgical planning

IMAGING RECOMMENDATIONS

  • MRI with contrast; MR spectroscopy (MRS), MR perfusion, functional MRI, and DTI are useful adjuncts

For more information, please see the corresponding chapter in Radiopaedia.

Contributor: Rachel Seltman, MD

DOI: https://doi.org/10.18791/nsatlas.v1.03.01.01

References

Louis DN, Ohgaki H, Wiestler OD, Cavenee WK, Burger PC, Jouvet A, et al. The 2007 WHO classification of tumours of the central nervous system. Acta Neuropathol 2007;114:547.

Nayak L, et al. Radiotherapy and temozolomide for anaplastic astrocytic gliomas. J Neurooncol 2015;123:129–134.

Ogura R, et al. Immunohistochemical profiles of IDH1, MGMT and P53: Practical significance for prognostication of patients with diffuse gliomas. Neuropathology 2015;35:324–335.

Osborn AG, Salzman KL, Jhaveri, MD. Diagnostic Imaging (3rd ed). Philadelpha, PA: Elsevier, 2016.

Arevalo-Perez J, Peck KK, Young RJ. Dynamic contrast-enhanced perfusion MRI and diffusion-weighted imaging in grading of gliomas. J Neuroimaging 2015;25:792–798.

Gempt J, et al. Multimodal imaging in cerebral gliomas and its neuropathological correlation. Eur J Radiol 2014;83:829–834.

Hirai T, et al. Prognostic value of perfusion MR imaging of high-grade astrocytomas: long-term follow-up study. AJNR Am J Neuroradiol 2008;29:1505–1510.

Tortosa A, et al. Prognostic implication of clinical, radiologic, and pathologic features in patients with anaplastic gliomas. Cancer 2003;97:1063–1071.

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