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Pilocytic astrocytomas: well-demarcated magnetic resonance appearance despite frequent infiltration histologically
K J Coakley1, J Huston, B W Scheithauer
1Department of Diagnostic Radiology, Mayo Clinic Rochester, Minnesota 55905, USA.
Objective:
To determine the magnetic resonance imaging (MRI) characteristics of pilocytic astrocytomas and to correlate them with the histopathologic findings.
Material And Methods:
MRI examinations and histopathologic findings in 56 patients with pilocytic astrocytomas were retrospectively reviewed. In 38 patients, findings on MRI were compared with those on computed tomography.
Results:
The tumors occurred at all levels of the central nervous system, including the spinal cord. The intracranial tumors were periventricular (73%) or periaqueductal (9%). All tumors were typical pilocytic astrocytomas and were grade 1 on the basis of the World Health Organization classification. At operation, they were often circumscribed and cystic. Radiologically, the tumors were well demarcated (96%), had benign morphologic features, and almost always showed enhancement (94%).
Conclusion:
MRI of pilocytic astrocytomas typically demonstrated a relatively large, sharply demarcated periventricular mass with pronounced contrast enhancement but minimal or no associated edema. Often, the tumors were cystic on MRI. Despite the well-demarcated appearance grossly and on MRI, pathologic review showed that many of these tumors (64%) infiltrated the surrounding parenchyma, particularly the white matter.
Insights
Magnetic resonance imaging (MRI) of pilocytic astrocytomas reveals well-demarcated, enhancing periventricular masses, often cystic. Despite imaging, 64% infiltrate surrounding brain tissue, highlighting the need for careful histopathologic correlation.
Area of Science:
- Neuroradiology
- Neuro-oncology
- Pathology
Background:
- Pilocytic astrocytomas are common pediatric brain tumors.
- Accurate imaging is crucial for diagnosis and treatment planning.
Purpose of the Study:
- To characterize magnetic resonance imaging (MRI) features of pilocytic astrocytomas.
- To correlate MRI findings with histopathologic characteristics.
Main Methods:
- Retrospective review of MRI and histopathology in 56 pilocytic astrocytoma patients.
- Comparison of MRI with CT in 38 patients.
Main Results:
- Tumors occurred throughout the central nervous system, frequently periventricular.
- MRI showed well-demarcated (96%), enhancing (94%) masses, often cystic.
- All tumors were World Health Organization grade 1.
Conclusions:
- MRI typically shows large, demarcated, enhancing, cystic periventricular masses with minimal edema.
- Despite imaging appearance, 64% of pilocytic astrocytomas infiltrate surrounding parenchyma.
- MRI findings correlate with histopathology but do not fully reveal tumor infiltration.