PILOCYTIC ASTROCYTOMAS - WELL-DEMARCATED MAGNETIC-RESONANCE APPEARANCE DESPITE FREQUENT INFILTRATION HISTOLOGICALLY

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 mere 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 mere typical pilocytic astrocytomas and were grade 1 on the basis of the World Health Organization classification, At operation, they mere often circumscribed and cystic, Radiologically, the tumors mere 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.