The Radiological Imaging Features of Easily Misdiagnosed Epithelioid Glioblastoma in Seven Patients.

OBJECTIVE: We review the radiological imaging features and report histopathological findings of 7 adult patients with epithelioid glioblastoma (eGBM), which was a newly revised subtype of glioblastoma.

METHODS: Seven adult patients with a diagnosis of eGBM on a brain tissue specimen were retrospectively confirmed by pathology. The tumor magnetic resonance imaging characteristics such as location, number, edema, necrosis, hemorrhage, enhancement, diffusion-weighted image, apparent diffusion coefficient, magnetic resonance spectroscopy, dynamic susceptibility contrast-perfusion-weighted imaging, and histopathological findings were documented.

RESULTS: The tumors of these patients exhibited iso-hyperintensive signal on the T2-weighted image and iso-hypointensive signal on the T1-weighted image. All the lesions manifested iso-hypointensive signal on the diffusion-weighted image, and 2 cases showed significantly restricted hyperintensive signal (2/7). Peritumoral edema in all cases was mild. Five cases were located in the cortical lobe (5/7) and the other 2 were multifocal (2/7). Four cases showed white matter collapse sign (4/7). These tumors revealed apparent enhancement after contrast injection. In particular, 4 cases displayed capsuled sign (4/7), 2 cases showed dura mater tail sign (2/7), and 1 case showed hemorrhage (1/7). The mean value of apparent diffusion coefficient in 6 cases was 1.09 × 10-3 mm2 /s. The mean value of relative cerebral blood volume in 3 cases was 2.84 × 10-3 mm2 /s on dynamic susceptibility contrast-perfusion-weighted imaging. The average value of the choline/N-acetyl aspartate ratio in 4 cases was 6.47 × 10-3 mm2 /s on magnetic resonance spectroscopy. All cases expressed a BRAF V600E mutation according to molecular characteristics.

CONCLUSIONS: eGBMs that were predominantly located in cortex with mild peritumoral edema, white matter collapse, encapsular sign, and dura mater tail sign could be easily misdiagnosed as cortex-involved intracranial brain tumor such as meningioma, whereas multifocal tumors could be easily misdiagnosed as metastatic tumor and lymphoma. Multimodal images were helpful for the differential diagnosis.