LAUSR

Objective To evaluate the frequency and malignancy rate of incidental focal uptake of 18F-fluorodeoxyglucose (FDG) in the breast on PET/computed tomography (CT). Material and methods All PET/CT scan reports from a single institution from 2010 to 2017 were electronically searched for words or phrases related to FDG uptake in the breast. Potentially eligible PET/CT scans were manually reviewed for the presence of focal incidental findings in the breast, and a final diagnosis was established based on pathology, clinical examinations, and clinical follow-up. Results A total of 19 551 PET/CT scans were reviewed, from which 66 patients (0.3%) presented with unexpected focal FDG-avid lesions of the breast. Fifty-three patients (80.3%) had follow-up evaluations. The final diagnosis showed malignancies in 38 patients. Thirty-four patients had biopsy-verified cancer (primary breast cancers, n = 30; metastasis, n = 4), and four patients with known lymphoma showed a tumour response in the breast after chemotherapy. The malignancy rate was 85.0% among patients who underwent biopsy (34 of 40 patients). The SUVmax was significantly higher in patients with a final malignant diagnosis (n = 38) than in those with a benign diagnosis (n = 15) (4.5 ± 2.9 vs. 2.7 ± 1.3, P = 0.03). Conclusion Incidental uptake of FDG in the breast was rare. However, the malignancy rate was high among these patients, particularly among patients who had a follow-up biopsy. We recommend biopsy or thorough follow-up in patients with incidental focal uptake of FDG in the breast.