The role of (18)F-FDG PET/CT in the diagnosis of breast cancer and lymph nodes metastases and micrometastases may be limited.

Our aim was to evaluate the diagnostic accuracy of fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography ((18)F-FDG PET/CT) in detecting primary invasive breast cancer (IBC) including invasive ductal breast cancer, invasive lobular breast cancer and axillary, internal mammary and supraclavicular lymph nodes. One hundred and sixty four patients with operable IBC and clinically negative lymph nodes were recruited and analyzed retrospectively. All patients underwent (18)F-FDG PET/CT scan, the results of which were compared with histopathology of dissected axillary lymph nodes (ALN). All patients were followed-up annually by ultrasonography, mammography and/or CT or MRI for relapse and distant metastases. Results showed that the (18)F-FDG PET/CT scans were positive in 141/164 (86%) patients and negative in 23/164 (14%) patients. The sensitivity of (18)F-FDG PET was 86% (141/164). Diagnostic performance of PET was significantly correlated with primary tumor grades and size (P:0.003 and P:0.0007, respectively). The sensitivity, specificity, overall accuracy, positive predictive value, and negative predictive value of (18)F-FDG PET/CT in ALN staging (SUVmax cutoff at 2.0) were 46.3%, 91.1%, 79.8%, 63.3%, and 83.6%, respectively. The false negative and false positive rate was 54% (22/41) and 9% (11/123), respectively. No relapse and metastases were found in a follow-up period of 2.42±2.56 months in patients with FN micrometastases in (18)F-FDG PET scan. In conclusion, (18)F-FDG PET/CT was useful in detecting the primary invasive breast cancer and its distant metastases but had a limited value in the axillary, internal mammary and supraclavicular lymph nodes. False negative (18)F-FDG PET scan in case of micrometastases and of metastases in ALN indicated good prognosis.