A 40-year-old man with AIDS presents with progressive headache and left hemiparesis. MRI shows a solitary homogeneously enhancing lesion in the right basal ganglia abutting the ventricular wall. Steroids given empirically cause marked shrinkage of the lesion on repeat imaging. What is the most likely diagnosis?

• A Cerebral toxoplasmosis
• B Metastatic carcinoma
• C Glioblastoma
• D Primary CNS lymphoma ✓

Explanation

Primary CNS lymphoma in immunocompromised patients is almost always EBV-positive diffuse large D-cell lymphoma, typically a solitary periventricular enhancing lesion that is exquisitely corticosteroid sensitive, often disappearing transiently ('ghost tumor'). Toxoplasmosis more often produces multiple ring-enhancing lesions with edema and does not melt dramatically with steroids alone. Glioblastoma shows thick irregular ring enhancement with necrosis, and metastases are usually multiple, cortical, and at gray-white junctions.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.