A 55-year-old immunocompetent woman presents with progressive hemiparesis. MRI shows a homogeneously enhancing periventricular mass abutting the lateral ventricle ependyma with markedly low signal on ADC map. MR spectroscopy shows elevated choline and a prominent lipid peak. Which diagnosis is most likely?
- A Toxoplasmosis
- B Glioblastoma multiforme
- C Primary central nervous system lymphoma ✓
- D Metastasis
Correct answer: C. Primary central nervous system lymphoma
Explanation
Primary CNS lymphoma in immunocompetent patients is characteristically periventricular, crosses the ependyma, enhances homogeneously, and shows marked diffusion restriction due to dense cellularity, giving very low ADC. A lipid peak reflects necrosis within high-grade lymphoma. Toxoplasma lesions are typically multiple, basal ganglia located, show ring rather than solid enhancement, and do not restrict diffusion as strongly, which is the key discriminator from this appearance.
Reference: Osborn's Brain: Imaging, Pathology, and Anatomy, 2nd ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.