Diffuse 'fibrillary' astrocytomas: correlation of MRI features with histopathologic parameters and tumor grade

MR images in 54 patients with biopsy-proven diffuse or 'fibrillary' astrocytomas were analyzed and compared with the histopathologic features in order to determine which histophathologic characteristics underlie the radiographic findings in these gliomas and whether radiographic findings are more closely correlated with individual histopathologic characteristics than with histologically determined tumor grade. The MRI features studied included tumor heterogeneity, edema, mass effect, border sharpness, 'anatomic invasion', contrast enhancement, hemorrhage, and the presence of flow voids, calcium and cyst formation. The histopathologic characteristic studied included cellular atypia, mitoses, cellularity, endothelial proliferation, necrosis and tumor grade. Edema (P<0.01), flow voids (P=0.02) and contrast enhancement (P<0.01) demonstrated a direct correlation with tumor grade, but edema (P<0.01) and contrast enhancement (P<0.01) also demonstrated a significant correlation to tumor cellularity. Tumor heterogeneity was associated with the presence of necrosis (P=0.01). Hemorrhage occurred only in high grade tumors, where it correlated with endothelial proliferation (P=0.04). (orig.)