False-positive finding of brain metastasis on (18)F-FDG PET imaging due to early subacute ischemic stroke

Area of Science:

• Neurology
• Nuclear Medicine
• Radiology

Background:

• Positron Emission Tomography (PET) with fluorodeoxyglucose (FDG) is widely used for cancer staging.
• Brain metastases are a common concern in lung cancer patients.
• Inflammatory processes can sometimes mimic hypermetabolism on FDG PET scans.

Observation:

• An FDG PET scan for a left lung mass revealed increased uptake in the left posterior fossa, initially suspicious for brain metastasis.
• Magnetic Resonance Imaging (MRI) subsequently identified restricted diffusion in the left cerebellum, indicative of a subacute ischemic stroke.
• Follow-up imaging demonstrated resolution of FDG uptake and evidence of encephalomalacia on MRI.

Findings:

• The hypermetabolic focus on FDG PET represented the inflammatory phase of a subacute ischemic stroke, not brain metastasis.
• This case highlights a rare instance of a false-positive FDG PET finding for brain metastasis.

Implications:

• Clinicians must consider ischemic stroke as a potential cause of false-positive FDG PET findings in the brain.
• MRI confirmation is essential when FDG PET reveals suspicious brain lesions, especially given overlapping clinical symptoms between stroke and metastasis.
• Accurate differentiation is critical for appropriate patient management and treatment planning.