Toxoplasmosis: This is a common opportunistic infection in immunocompromised patients, especially those with HIV/AIDS, causing mass enhancing lesions in the brain due to the formation of abscesses.

Cysticercosis: Caused by the pork tapeworm Taenia solium, this infection can lead to the formation of cysts in the brain that may appear as mass enhancing lesions on imaging, especially in endemic areas.
Pyogenic Brain Abscess: Bacterial infections can cause abscesses in the brain, which may present as mass enhancing lesions, particularly in patients with a history of trauma, surgery, or immunocompromise.
Tuberculous Abscess: In areas where tuberculosis is prevalent, brain abscesses caused by Mycobacterium tuberculosis can occur, presenting as mass enhancing lesions.

Neurocysticercosis with a Large Cyst: Although less common, a large cysticercus cyst can mimic a tumor or abscess and is critical to diagnose due to its potential for severe neurological consequences if not treated properly.
Cerebral Malaria: In patients traveling from or living in malaria-endemic areas, cerebral malaria can cause mass lesions due to sequestration of infected red blood cells in the brain, which is life-threatening and requires immediate treatment.
Brain Abscess due to Nocardia: Nocardia species can cause brain abscesses, particularly in immunocompromised patients, and are important to identify due to their resistance to many antibiotics and the need for specific treatment.

Paragonimiasis: A parasitic infection caused by lung flukes of the genus Paragonimus, which can rarely affect the brain and cause mass enhancing lesions.
Schistosomiasis: In rare cases, Schistosoma species can infect the brain, leading to the formation of granulomas or abscesses that may appear as mass enhancing lesions on imaging.
Echinococcosis (Hydatid Disease): Caused by the Echinococcus tapeworm, this infection can lead to the formation of cysts in various parts of the body, including the brain, although brain involvement is rare.