An 84 y.o. white male with chronic lymphocytic leukemia (CLL) was admitted to the hospital for fever, headache, and malaise.

The patient had been diagnosed with CLL ten years previously, and his most recent chemotherapy (three months prior) had consisted of ritxuximab and bendamustine. Before that he had been treated with fludarabine.

Fevers and night sweats had been present intermittently for several weeks, and severe headache had been present for one to two weeks prior to admission. Three weeks prior to admission PCR for CMV and aspergillus galactomannan antigen assay had been negative. Headache and fever had not appeared to benefit from a course of amoxicillin/clavulanate intended for possible sinusitis. He had not had significant cough.

The patient was born and raised in Missouri but by the time of his hospitalization had been a long term resident of the Willamette Valley of Oregon. He was a retired university professor. His past medical history was notable for pulmonary tuberculosis diagnosed shortly after his World War II service in the U.S. Navy. He was treated at the time with therapeutic pneumothorax. After his diagnosis of CLL he received a course of INH for latent TB. He also had history of colectomy for diverticular disease.

At the time of admission the patient was somewhat confused. Laboratory data were notable for pancytopenia (WBC 1.7, Hgb 10.6, Plts 63). An MRI of the brain was unremarkable. A CT scan of the chest showed left sided volume lost (history of therapeutic pneumothorax) and three pulmonary nodules, the largest of which was 2.7 cm in greatest dimension (see image upper left). Results of CSF analysis included WBC 238 (87% lymphocytes), protein 133 mg/dL, glucose 61 mg/dL. CSF gram stain is pictured at lower left. The patient underwent a percutaneous biopsy of the right lung mass.

Of the choices below what the likely the cause of this illness?