Predominantly cystic glioblastoma mimicking benign cystic lesions: A radiological diagnostic challenge.

Glioblastoma multiforme (GBM) is the most common and most aggressive primary malignant brain tumor in adults. Although it typically presents as a heterogeneously enhancing solid mass with central necrosis, predominantly cystic glioblastoma is an uncommon morphological variant that may mimic other cystic intracranial lesions and create diagnostic uncertainty. We report the case of a 58-year-old man who presented with headache and vomiting for 1 week's duration. Laboratory investigations, including complete blood count, erythrocyte sedimentation rate, C-reactive protein, and total white blood cell count, were within normal limits. Magnetic resonance imaging demonstrated a large predominantly cystic intra-axial lesion in the left frontal lobe with thick irregular peripheral enhancement, extensive surrounding vasogenic edema, and marked mass effect. Diffusion-weighted imaging demonstrated facilitated diffusion within the cystic component, favoring a neoplastic process over abscess. The patient underwent surgical excision, and histopathological examination confirmed glioblastoma (WHO grade 4). This case highlights the importance of recognizing atypical cystic presentations of glioblastoma and emphasizes the role of diffusion-weighted imaging in differentiating cystic neoplasms from other ring-enhancing intracranial lesions.