A 38-year-old HIV-positive man with CD4 count below 100 cells/microliter presents with focal neurological deficits and altered mentation. MRI shows multiple ring-enhancing lesions with surrounding edema involving the basal ganglia. Empirical antitoxoplasma therapy fails after two weeks. Brain biopsy would most likely show:

• A Large immunoblastic B cells positive for CD20 with EBV-encoded RNA expression ✓
• B Multinucleated giant cells containing mycobacteria on Ziehl-Neelsen stain
• C Enlarged oligodendrocytes with ground-glass nuclear inclusions
• D Coagulative necrosis with tachyzoites highlighted by immunohistochemistry

Explanation

In AIDS patients, failure of a basal ganglia ring-enhancing lesion to respond to antitoxoplasma therapy raises suspicion of primary central nervous system lymphoma, an EBV-associated diffuse large B-cell lymphoma expressing CD20 and EBER. Toxoplasma abscesses should shrink within two weeks of therapy. Ground-glass oligodendrocyte inclusions indicate PML, a non-enhancing demyelinating process, killing option C.

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.