The sagittal T1 post-contrast MRI of the brain shown above reveals a large, irregularly enhancing mass with central necrosis in the frontal lobe. Which of the following is the most likely diagnosis?

Explanation

## Image Findings * Sagittal T1 post-contrast MRI of the brain. * Large, irregular, thick, peripheral (ring-like) enhancement in the superior frontal lobe. * Central non-enhancing necrotic or cystic component within the lesion. * Significant mass effect on adjacent brain parenchyma (implied by lesion size and morphology). * No clear evidence of multiple lesions. ## Diagnosis **Key Point:** The MRI findings of a large, irregularly enhancing mass with central necrosis and significant mass effect are highly characteristic of **Glioblastoma Multiforme (GBM)**. Glioblastoma is the most common and aggressive primary brain tumor in adults. On post-contrast T1 MRI, it typically presents as a **heterogeneously enhancing mass** with a **thick, irregular, "shaggy" peripheral enhancement** surrounding a **central necrotic core**. There is often extensive **peritumoral edema** (best seen on T2/FLAIR, but implied by mass effect) and it can cross the corpus callosum, forming a "butterfly glioma." The irregular and thick enhancement is a hallmark differentiating it from other ring-enhancing lesions. ## Differential Diagnosis | Feature | Glioblastoma Multiforme | Cerebral Abscess | Solitary Brain Metastasis | Tumefactive Demyelinating Lesion | | :---------------------- | :---------------------------------------------------- | :------------------------------------------------------ | :------------------------------------------------------ | :---------------------------------------------------- | | **Enhancement Pattern** | Thick, irregular, "shaggy" peripheral ring | Thin, smooth, regular ring | Often smooth, uniform ring; can be irregular | Incomplete/open ring (facing cortex) | | **Central Core** | Necrosis (non-restricting diffusion) | Necrosis/pus (restricted diffusion on DWI) | Necrosis or cystic component | Edema/demyelination | | **Perilesional Edema** | Often extensive | Variable, often significant | Often extensive, disproportionate to lesion size | Variable, can be extensive | | **Location** | Often supratentorial, can cross midline | Any location, often at gray-white matter junction | Often at gray-white matter junction, multiple common | White matter, often periventricular | | **Clinical Context** | Rapidly progressive neurological deficits | Fever, infection, immunocompromised state | History of primary malignancy | History of MS, relapsing-remitting course | ## Clinical Relevance **Clinical Pearl:** Glioblastoma multiforme is a WHO Grade IV astrocytoma with a very poor prognosis, despite aggressive treatment involving surgery, radiation, and chemotherapy (temozolomide). Early diagnosis and intervention are crucial for symptom management and extending survival. ## High-Yield for NEET PG **High-Yield:** The classic MRI appearance of GBM is a **heterogeneously enhancing, irregularly marginated mass with central necrosis and extensive peritumoral edema**. **Key Point:** The **thick, irregular, "shaggy" enhancement** is a key feature distinguishing GBM from other ring-enhancing lesions like abscesses (thin, smooth rim) or metastases (often smoother, more uniform). ## Common Traps **Warning:** Do not confuse the irregular, thick enhancement of GBM with the thin, smooth rim of an abscess. Also, while metastases can be solitary and ring-enhancing, the degree of irregularity and "shagginess" often points more towards GBM, especially in the absence of a known primary malignancy. ## Reference [cite:Osborn's Brain, Ch 11]