Which MRI finding with gadolinium is characteristic of glioblastoma?

• A. A uniform, well-circumscribed lesion
• B. A heterogeneous mass with peripheral enhancement and central necrosis
• C. A small, calcified lesion
• D. A lesion without enhancement

Answer: (B)

High-grade glioblastoma on gadolinium-enhanced MRI typically shows a heterogeneous mass with irregular, peripheral enhancement surrounding a central necrotic core. This ring-like enhancement arises because the tumor disrupts the blood–brain barrier, allowing contrast to accumulate at the active tumor rim while the necrotic center remains non-enhancing. The surrounding edema further accentuates the appearance and often contributes to mass effect.

Other patterns don’t fit as well: a uniform, well-circumscribed lesion suggests a less aggressive or extra-axial process; a small calcified lesion points toward oligodendroglioma; a lesion without enhancement is more typical of a lower-grade glioma or another non-neoplastic process.