Background/aim: We aimed to evaluate the role of FDG PET/CT in the detection of extraaxillary regional nodal/distant metastasis in breast cancer patients and to assess the value of FDG PET/CT for detecting distant metastases in patient subgroups. Materials and methods: A total of 254 patients with breast cancer (248 female, 6 male) who underwent PET/CT for initial staging were enrolled. Patients were divided into four groups: Group 1 consisted of 154 patients diagnosed by tru-cut/core/FNAB,

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... p 2 comprised 32 patients diagnosed by excisional biopsy, Group 3 included 62 patients who had mastectomy-axillary lymph node dissection, and Group 4 consisted of 6 patients who had axillary lymph node metastasis diagnosed by excisional biopsy. Results: PET/CT detected distant metastasis in 76 of the 254 patients. Of these patients, 21.7% had bone/bone marrow metastasis, 7.1% had lung metastasis, 13% had mediastinal lymph node metastasis, 4.8% had liver metastasis, 9.8% had other organ/system metastasis, and 6% had other lymphadenopathies. According to T staging, the percentages of distant metastasis were as follows: 13.6% of the 66 T1 stage patients, 35.7% of the 129 T2 stage patients, 40% of the 20 T3 stage patients, and 33.3% of the 39 T4 stage patients. Conclusion: FDG-PET/CT led to a change in the stage of disease and the treatment approach in newly diagnosed breast cancer patients due to its superiority in detecting extraaxillary regional lymph node metastases and distant metastases.