Gestational or pregnancy‑associated breast cancer is defined as breast cancer that is diagnosed during pregnancy, in the first post‑partum year or any time during lactation. We report a rare imaging finding of breast cancer seen on fluorodeoxyglucose‑positron emission tomography/computed tomography (FDG PET/CT) study in a 32‑year‑old lactating woman. The FDG PET/CT study demonstrated uptake in the soft tissue lesion noted in the right breast corresponding to the primary lesion and multiple nodes in the bilateral axilla, right supraclavicular and mediastinum. In addition, there was FDG tracer uptake in both the breast parenchyma related to breast feeding. This case illustrates the first case of breast cancer in a lactating woman described in FDG PET/CT.