Breast Abscess Mimicking Malignancy on FDG PET/CT in a Patient with Follicular Lymphoma Undergoing Chemotherapy

We report a diagnostically challenging case of a 43-year-old woman with follicular lymphoma undergoing chemotherapy, who achieved complete metabolic response of all initial disease sites on follow-up fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/ CT).However, a newly developed necrotic, FDG-avid lesion in the right breast raised strong suspicion of malignancy. Further evaluation, including ultrasound and histopathology, confirmed it to be a breast abscess. This case highlights the diagnostic challenges posed by false-positive FDG PET/ CT findings in immunocompromised patients and underscores the importance of integrating clinical assessments, imaging results, and pathological evaluations when investigating new hypermetabolic lesions.