eMedicine Specialties > Oncology > Carcinomas of the Central and Peripheral Nervous System

Astrocytoma: Differential Diagnoses & Workup

Author: Benjamin Kennedy,, Columbia University College of Physicians and Surgeons
Coauthor(s): Jeffrey N Bruce, MD, Edgar M Housepian Professor of Neurological Surgery Research, Professor of Neurological Surgery, Director of Brain Tumor Tissue Bank, Director of Bartoli Brain Tumor Laboratory, Department of Neurosurgery, Columbia University College of Physicians and Surgeons
Contributor Information and Disclosures

Updated: Jan 23, 2009

Differential Diagnoses

Other Problems to Be Considered

Arteriovenous malformation
Brainstem gliomas
Cavernous angioma
Cavernous malformation
Cerebral abscess
CNS lymphoma
Encephalitis
Ependymoma
Epidural abscess
Glioblastoma multiforme
Hamartoma
Intracranial hemorrhage
Meningioma
Metastasis
Multiple sclerosis
Oligodendroglioma
Radiation necrosis
Subdural empyema
Stroke or infarct
Toxoplasmosis

Workup

Laboratory Studies

  • No laboratory studies are diagnostic of astrocytoma. Baseline laboratory studies, including Chem 7, CBC, prothrombin time (PT), and activated partial thromboplastin time (aPTT), may be obtained for general metabolic surveillance and preoperative assessment.

Imaging Studies

  • CT scans and MRI (with and without contrast) are helpful in the diagnosis, grading, and pathophysiological evaluation of astrocytomas. MRI is considered the criterion standard, but a CT scan may be useful in the acute setting or when MRI is contraindicated.
  • On a CT scan, low-grade astrocytomas appear as poorly defined, homogeneous, low-density masses without contrast enhancement. However, slight enhancement, calcification, and cystic changes may be evident early in the course of the disease. In cases where a cortically based enhancing mass is discovered, particularly in cases where multiple lesions are identified, the possibility of metastatic disease must be considered. Systemic imaging, generally consisting of a contrast-enhanced CT scan of the chest, abdomen, and pelvis, may be warranted to evaluate for the possibility of an alternate primary lesion.
  • Similarly, anaplastic astrocytomas may appear as low-density lesions or inhomogeneous lesions, with areas of both high and low density within the same lesion. Unlike low-grade lesions, partial contrast enhancement is common.
  • Astrocytomas are generally isointense on T1-weighted images and hyperintense on T2-weighted images. While low-grade astrocytomas uncommonly enhance on MRI, most anaplastic astrocytomas enhance with paramagnetic contrast agents. New methods are being developed to assess tumor vascularity by MRI, including techniques such as arterial-spin labeling (ASL) and dynamic contrast-enhanced MRI.
  • Angiography may be used to rule out vascular malformations and to evaluate tumor blood supply. A normal angiographic pattern or a pattern consistent with an avascular mass that displaces normal vessels is usually observed with both low-grade and high-grade lesions. In rare instances, a tumor blush may be observed with high-grade lesions.
  • Imaging has also taken a larger role in the operating room, as many procedures are now performed with intraoperative image guidance based upon high-resolution MRIs. In addition, intraoperative MRI and CT scans are being tested for utility in guiding the extent of resection and presence of residual tumor during the surgical procedure.
  • Ultimately, the boundaries of infiltrating tumors extend far beyond what can be seen by imaging studies. New methods of tumor imaging are being developed to specifically tag or label tumor cells so they may be visualized in the operating room. Such methods include pretreatment of the patient with dyes or tumor-specific proteins tagged with fluorescent molecules.

Axial CT scan, precontrast and postcontrast, show...

Axial CT scan, precontrast and postcontrast, shows a low-grade astrocytoma of the left frontal lobe. The tumor is nonenhancing.

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Axial CT scan, precontrast and postcontrast, show...

Axial CT scan, precontrast and postcontrast, shows a low-grade astrocytoma of the left frontal lobe. The tumor is nonenhancing.


Coronal postcontrast T1-weighted MRI shows a low-...

Coronal postcontrast T1-weighted MRI shows a low-grade astrocytoma in the right inferior frontal lobe just above the sylvian fissure. No enhancement is present post–gadolinium administration.

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Coronal postcontrast T1-weighted MRI shows a low-...

Coronal postcontrast T1-weighted MRI shows a low-grade astrocytoma in the right inferior frontal lobe just above the sylvian fissure. No enhancement is present post–gadolinium administration.


Axial T2-weighted MRI shows a low-grade astrocyto...

Axial T2-weighted MRI shows a low-grade astrocytoma of the inferior frontal lobe with mild mass effect and no surrounding edema.

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Axial T2-weighted MRI shows a low-grade astrocyto...

Axial T2-weighted MRI shows a low-grade astrocytoma of the inferior frontal lobe with mild mass effect and no surrounding edema.


Other Tests

  • Because seizure activity is often associated with astrocytomas, EEG may be employed to evaluate and monitor epileptiform activity.
  • Radionuclide scans, such as positron emission tomography (PET), single-photon emission tomography (SPECT), and technetium-based imaging, can permit study of tumor metabolism and brain function. PET and SPECT may be used to distinguish a solid tumor from edema, to differentiate tumor recurrence from radiation necrosis, and to localize structures.
  • Metabolic activity determined by radionuclide scans can be used to determine the grade of a lesion. Hypermetabolic lesions often correspond to higher-grade tumors.
  • ECG and chest radiographs are indicated to evaluate operative risk.

Procedures

  • A lumbar puncture (LP) in patients with cerebral astrocytomas should be approached with extreme caution because of the risk of downward cerebral herniation secondary to elevated ICP. Although CSF studies are not employed in the diagnosis of astrocytomas, they may be employed to rule out other possible diagnoses, such as metastasis, lymphoma, or medulloblastoma.

Histologic Findings

Four histological variants of low-grade astrocytomas are recognized—protoplasmic, gemistocytic, fibrillary, and mixed.14

  1. Protoplasmic astrocytomas are generally cortically based, with cells containing prominent cytoplasm. Protoplasmic astrocytomas constitute approximately 28% of infiltrating astrocytomas.
  2. Gemistocytic astrocytomas are generally found in the cerebral hemispheres in adults and are composed of large round cells with eosinophilic cytoplasm and eccentric cytoplasm. Gemistocytic astrocytomas constitute 5-10% of hemispheric gliomas.
  3. Fibrillary astrocytomas, the most frequent histological variant, resemble cells from the cerebral white matter and are composed of small, oval, well-differentiated cells. The tumors are identified by a mild increase in cellularity and fibrillary background. Markers for glial fibrillary acidic protein (GFAP) are used to identify fibrillary astrocytomas.
  4. Compared to low-grade lesions, anaplastic astrocytomas show a marked tendency for regional or diffuse hypercellularity. Furthermore, anaplastic astrocytomas show increased anaplasia, demonstrated by increased nuclear complexity, the presence of mitoses, increased cytoplasmic variability, and increased endothelial cell proliferation.

Low-grade fibrillary astrocytoma and low cellular...

Low-grade fibrillary astrocytoma and low cellularity with minimal nuclear atypia.

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Low-grade fibrillary astrocytoma and low cellular...

Low-grade fibrillary astrocytoma and low cellularity with minimal nuclear atypia.


Fibrillary astrocytoma with microcyst formation.

Fibrillary astrocytoma with microcyst formation.

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Fibrillary astrocytoma with microcyst formation.

Fibrillary astrocytoma with microcyst formation.


Gemistocytic astrocytoma tumor cells have eosinop...

Gemistocytic astrocytoma tumor cells have eosinophilic cytoplasm with nuclei displaced to the periphery.

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Gemistocytic astrocytoma tumor cells have eosinop...

Gemistocytic astrocytoma tumor cells have eosinophilic cytoplasm with nuclei displaced to the periphery.


Characteristic pilocytic astrocytoma, long bipola...

Characteristic pilocytic astrocytoma, long bipolar tumor cells, and Rosenthal fibers.

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Characteristic pilocytic astrocytoma, long bipola...

Characteristic pilocytic astrocytoma, long bipolar tumor cells, and Rosenthal fibers.


Anaplastic astrocytoma with high cellularity with...

Anaplastic astrocytoma with high cellularity with marked nuclear atypia.

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Anaplastic astrocytoma with high cellularity with...

Anaplastic astrocytoma with high cellularity with marked nuclear atypia.


Staging

Staging is not performed or described for patients with astrocytoma. The histologic grade of the tumor is of primary importance when determining prognosis. Unlike other systemic tumors, distant or extracranial metastasis of astrocytomas is exceedingly rare. Clinical decline and tumor-associated morbidity and mortality are almost always associated with local mass effects on the brain by a locally recurrent intracranial tumor.

More on Astrocytoma

Overview: Astrocytoma
Differential Diagnoses & Workup: Astrocytoma
Treatment & Medication: Astrocytoma
Follow-up: Astrocytoma
Multimedia: Astrocytoma
References
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Further Reading

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Keywords

low-grade astrocytoma, fibrillary astrocytoma, gemistocytic astrocytoma, protoplasmic astrocytoma, diffuse astrocytoma, pilocytic astrocytoma, pilocystic astrocytoma, juvenile pilocytic astrocytoma, anaplastic astrocytoma, glioblastoma multiforme, CNS neoplasm, CNS cancer, CNS malignancy, immortalized astrocyte

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Contributor Information and Disclosures

Author

Benjamin Kennedy,, Columbia University College of Physicians and Surgeons
Disclosure: Nothing to disclose.

Coauthor(s)

Jeffrey N Bruce, MD, Edgar M Housepian Professor of Neurological Surgery Research, Professor of Neurological Surgery, Director of Brain Tumor Tissue Bank, Director of Bartoli Brain Tumor Laboratory, Department of Neurosurgery, Columbia University College of Physicians and Surgeons
Jeffrey N Bruce, MD is a member of the following medical societies: American Association for the Advancement of Science, American Association of Neurological Surgeons, Congress of Neurological Surgeons, New York Academy of Sciences, North American Skull Base Society, Society for Neuro-Oncology, and Southwest Oncology Group
Disclosure: NIH Grant/research funds Other

Medical Editor

Robert C Shepard, MD, FACP, Associate Professor of Medicine in Hematology and Oncology at University of North Carolina at Chapel Hill; Vice President of Scientific Affairs, Therapeutic Expertise, Oncology, at PRA International
Robert C Shepard, MD, FACP is a member of the following medical societies: American Association for Cancer Research, American College of Physician Executives, American College of Physicians, American Federation for Clinical Research, American Federation for Medical Research, American Medical Association, American Medical Informatics Association, American Society of Hematology, Association of Clinical Research Professionals, Eastern Cooperative Oncology Group, European Society for Medical Oncology, Massachusetts Medical Society, and Society for Biological Therapy
Disclosure: Nothing to disclose.

Pharmacy Editor

Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine
Disclosure: eMedicine Salary Employment

CME Editor

Rajalaxmi McKenna, MD, FACP, Southwest Medical Consultants, SC, Department of Medicine, Good Samaritan Hospital, Advocate Health Systems
Rajalaxmi McKenna, MD, FACP is a member of the following medical societies: American Society of Clinical Oncology, American Society of Hematology, and International Society on Thrombosis and Haemostasis
Disclosure: Nothing to disclose.

Chief Editor

Jules E Harris, MD, Clinical Professor of Medicine, Division of Hematology/Medical Oncology, Department of Internal Medicine, University of Arizona College of Medicine at Tucson; Consulting Staff, Arizona Cancer Center
Jules E Harris, MD is a member of the following medical societies: American Association for Cancer Research, American Association for the Advancement of Science, American Association of Immunologists, American Society of Hematology, and Central Society for Clinical Research
Disclosure: GlobeImmune Salary Consulting; Amplimed Consulting fee Consulting; FibroGen Consulting fee Consulting

 
 
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