Review Question - QID 108602

A 52-year-old male presents to his primary care provider for a follow-up appointment. 2 weeks ago, the patient experienced his first partial seizure, and the work-up revealed the finding seen in Figure A. His past medical history is significant for HIV (CD4: 89/mm^3), IV drug use, hypertension, hyperlipidemia, and chronic obstructive pulmonary disease. The patient has a positive IgG titer to Toxoplasma and has been on pyrimethamine-sulfadiazine as empiric treatment for toxoplasma encephalitis for 10 days. The patient's follow-up head imaging shows no reduction in the size of the lesion. Before the last few weeks, the patient has not had any opportunistic infections other than a hospitalization several months ago for pneumonia that the patient reports was "fungal." The patient's family history is significant for a paternal uncle who died of glioblastoma at the age of 55. Which of the following is the most appropriate next step?