Brain Tumors on MRI: a Practical Pattern-Recognition Playbook for Faster Reporting

The rapid workflow (60–120 seconds)

MRI is unbeatable for brain tumor work because it lets you “read the biology” — cellularity, vascularity, breakdown of the blood–brain barrier, hemorrhage, necrosis, and infiltration — without picking up a scalpel. The challenge is time: you need a fast, repeatable way to turn sequences into a confident, structured report. This playbook is a pattern-recognition workflow you can run in minutes. It’s not a textbook. It’s a practical decision tree built for real reporting: “What am I looking at? How aggressive is it? Where does it originate? What’s the differential? What should the clinician do next?”

Step 1 — Anchor the lesion

1. Intra-axial: glioma spectrum, metastasis, lymphoma, mimics.
2. Extra-axial: meningioma, schwannoma, SFT, dural metastasis.
3. Intraventricular: ependymoma, subependymoma, neurocytoma.

Quick extra-axial checks: CSF cleft, broad dural base, dural tail, hyperostosis, displaced cortex/vessels.

Step 2 — Classify enhancement

1. None/minimal: low-grade glioma, early infiltrative lesions.
2. Solid avid: meningioma, lymphoma, some mets.
3. Ring: GBM, metastasis, abscess, tumefactive demyelination.
4. Nodule + cyst: pilocytic astrocytoma, hemangioblastoma.

Pattern families you’ll use daily

Treat these as “default routes” in your differential. Start here, then adjust with patient context and advanced sequences.

A) Thick irregular ring + infiltration

GBM favored

1. Thick, irregular rim; central necrosis.
2. FLAIR extends beyond enhancement (infiltration).
3. Often elevated perfusion in the rim.

Key alternatives: necrotic metastasis (more circumscribed), abscess (restricted core), tumefactive demyelination (open ring).

B) Multiple lesions at gray–white junction

Metastases first

1. Multiple well-defined lesions with vasogenic edema.
2. Some hemorrhagic on SWI (primary-dependent).
3. Perfusion commonly elevated in viable components.

Report: number (or “numerous”), largest lesion, hemorrhage status, and recommend systemic workup if primary unknown.

Differential ladder (fast narrowing)

1. Compartment: extra-axial vs intra-axial vs ventricular.
2. Multiplicity: single vs multiple; junctional distribution suggests mets.
3. Enhancement: none / solid / ring / nodule+cyst.
4. Diffusion: restricted solid (lymphoma) vs restricted core (abscess).
5. Perfusion: high rCBV supports aggressive tumor; low supports some mimics.
6. SWI/CT correlation: hemorrhage/calcification (consider non-contrast CT if needed).
7. Context: age, immune status, known primary, symptom tempo.