Fluorodeoxyglucose positron emission tomography – computed tomography (FDG PET-CT) negative orbital metastasis secondary to breast carcinoma: a diagnostic pitfall

Orbital metastases from breast carcinoma are uncommon and often present diagnostic challenges. Fluorodeoxyglucose positron emission tomography - computed tomography (FDG PET-CT) is widely used in oncologic imaging, but may fail to detect small or metabolically inactive orbital lesions. We report a 41 -year-old female with a history of hormone receptor-positive invasive lobular breast carcinoma who presented with a painless progressive swelling of the lower eyelid and proptosis over 3 months. Magnetic resonance imaging (MRI) orbit revealed a lesion in the inferolateral aspect of the left lower eyelid and extraconal compartment of the left orbit. FDG PET-CT did not demonstrate any metabolic activity in the orbit. A biopsy was performed, confirming metastatic breast carcinoma. The patient underwent external beam radiotherapy directed at the eyelid and orbital region, resulting in a favorable clinical response. This case illustrates the limitations of FDG PET-CT in detecting orbital metastasis from breast carcinoma, particularly in lobular subtypes ,and emphasizes the importance of correlating imaging with clinical suspicion and biopsy in such clinical scenarios.<b>Abbreviations</b>: FDG PET-CT= Fluorodeoxyglucose positron emission tomography - computed tomography, MRI= Magnetic resonance imaging,ILC= Invasive lobular carcinoma, IDC= Invasive ductal carcinoma.