After 10 days of empiric therapy, the patient's clinical situation has not improved significantly and the appearance of the brain lesions on MRI is unchanged. Results for Toxoplasma serology and polymerase chain reaction (PCR) testing are negative. Cerebrospinal fluid PCR analysis for Epstein-Barr virus is positive. Tissue biopsy from the frontal lobe lesions would likely predominantly show an abnormal population of which of the following cells?

Question

After 10 days of empiric therapy, the patient's clinical situation has not improved significantly and the appearance of the brain lesions on MRI is unchanged.  Results for Toxoplasma serology and polymerase chain reaction (PCR) testing are negative.  Cerebrospinal fluid PCR analysis for Epstein-Barr virus is positive.  Tissue biopsy from the frontal lobe lesions would likely predominantly show an abnormal population of which of the following cells?

Quizplus · Accepted Answer

In a patient with HIV and multiple ring-enhancing lesions being treated empirically for toxoplasmosis, lack of a clinical or imaging response after 1-3 weeks of therapy should raise suspicion for other conditions requiring further evaluation, especially given negative Toxoplasma serologies. Primary central nervous system lymphoma (PCNSL) is the second most common cause of ring-enhancing lesions with mass effect in HIV. Classically, large, solitary lesions are more likely to suggest PCNSL rather than toxoplasmosis; however, multiple lesions (as seen in this patient) are also common in PCNSL. PCNSL is a diffuse, large-cell non-Hodgkin lymphoma of B-cell origin that usually occurs as a late complication of HIV infection. Epstein-Barr virus (EBV) is identified in almost all cases. Diagnosis of PCNSL can be made by positive EBV polymerase chain reaction analysis in the cerebrospinal fluid. Definitive diagnosis requires brain biopsy. Although EBV infections in general can be associated with abnormal T-lymphocytes (eg, atypical lymphocytes), T cell infiltration is not commonly seen on brain tissue biopsy of patients with HIV who have PCNSL. T-lymphocytes are the malignant cells in AIDS-associated T-cell lymphoma, not PCNSL (Choice E). (Choice B) Eosinophils do not give rise to solid tumors. (Choice C) Macrophages are the primary cell population in histiocytomas. Patients with Langerhans cell histiocytosis may develop eosinophilic granulomas that preferentially affect the skull, but ring-enhancing lesions are not seen. (Choice D) Oligodendrocytes can form oligodendrogliomas. Astrocytes are the precursor cells for glioblastoma multiforme, which can present with a ring-enhancing lesion. Educational objective: Primary central nervous system lymphoma is typically composed of B-lymphocytes. __________ References: Epstein-Barr virus in AIDS-related primary central nervous system lymphoma. (http://www.ncbi.nlm.nih.gov/pubmed/1681341) T-cell infiltration of primary CNS lymphoma. (http://www.ncbi.nlm.nih.gov/pubmed/8614509)

After 10 Days of Empiric Therapy, the Patient's Clinical Situation