Multiple etiologies can coexist and trigger CNS symptoms in individuals infected with HIV. This article reviews a case of a cerebellar mass in an HIV patient who, on biopsy, grew methicillin-resistant Staphylococcus aureus (MRSA) and by pathology, showed an atypical lymphoplasmacytic infiltrate concerning a clonal lymphoproliferative process, which may be a precursor of CNS lymphoma. The patient, a 36-year-old male with multiple comorbidities including HIV Infection, presented to the hospital for evaluation of a one-week course of headache and photophobia. Remarkable physical examination findings included dilated pupils and anisocoria. Initial CT brain imaging revealed vasogenic edema seen throughout the left cerebellar hemisphere provoking mass effect on the fourth ventricle and pontocerebellar cistern resulting in mild hydrocephalus, new findings compared to prior. MRI brain displayed a T1 isointense, T2 hypointense ring-enhancing lesion in the left cerebellar hemisphere, with restricted diffusion, and surrounding vasogenic edema resulting in mass effect over the fourth ventricle, left cerebellar peduncle, and pontocerebellar cistern causing mild hydrocephalus. The patient underwent left suboccipital craniotomy with evacuation of the cerebellar lesion by neurosurgery. Tissue cultures grew MRSA. Pathology was sent to New York-Presbyterian Columbia University Irving Medical Center due to the presence of atypical lymphoplasmacytic infiltrates. The final diagnosis was polyclonal B-cell population in the sample; however, prominent peaks were also seen above the polyclonal background, possibly representing a clonal proliferation. Therefore, the lymphoplasmacytic infiltrates remained atypical and the possibility of the underlying clonal lymphoproliferative process could not be entirely ruled out.