Primary central nervous system lymphoma is a rare brain tumor, primarily seen in immunocompromised patients (e.g., AIDS, organ transplantation). Patients present with headaches, seizures, or focal neurological deficits. The tumor can involve the deep white matter, the meninges, and the eye. If it involves the deep white matter, it may spread across the corpus callosum, similar to the pattern seen in glioblastoma multiforme.