Glioblastoma without Remarkable Contrast Enhancement on Magnetic Resonance Imaging

This is the report of a histological and clinical investigation of 4 cases of glioblastoma, a rare tumor, in whom poor contrast enhancement of the tumor was visualized on magnetic resonance imaging (MRI). Among the 94 patients with first-occurrence glioblastoma treated between January 2000 and August 2011, 4 were enrolled in this retrospective study. There were 2 men and 2 women, ranging in age from 41 to 70 years (mean, 57 years). All the patients underwent tumor resection, postoperative irradiation, and chemotherapy. One died of local tumor recurrence after 36 months; the remaining three remain alive as of 25 to 72 months after the initial treatment. The histopathology was glioblastoma with nuclear pleomorphism and pseudopalisading necrosis in all cases. However, the typical vascular endothelial proliferation was not found in 3 cases. All glioblastomas were immunopositive for p53 and immunonegative for epidermal growth factor receptor (EGFR) and isocitrate dehydrogenase 1 (IDH1). These glioblastomas showing unclear contrast enhancement on MRI had similar clinical and pathological characteristics, but differed in characteristics from glioblastoma patients showing marked contrast enhancement of the tumor on MRI.