Mammography and ultrasonography evaluation of unexpected focal 18F-FDG uptakes in breast on PET/CT

BACKGROUND: Unexpected focal 18F-FDG breast uptakes are occasionally identified on PET/CT due to its increased use for cancer staging and follow-up. The need for their characterization has been suggested. PURPOSE: To retrospectively evaluate the diagnostic value of ultrasonography (US) in distinguishing benign from malignant lesions for unexpected focal 18F-FDG uptakes in breast on PET/CT scans. MATERIAL AND METHODS: Between April 2004 and January 2010, 27 focal 18F-FDG breast uptakes in 27 patients (age range 33-62 years; mean age 46 years) among 5214 patients who had undergone PET/CT scans were retrospectively analyzed. The American College of Radiology (ACR) Breast Imaging-Reporting and Data System (BI-RADS) final assessment categories of the US and the maximum standardized uptake values (SUVs) of the lesions were compared between the benign and malignant lesions. RESULTS: Of the 27 lesions, 15 (56%) lesions were malignant. The rate of malignancy, according to the final assessment category on the US, was 0% (0 of 6) for category 3, 60% for category 4 (9 of 15), and 100% (6 of 6) for category 5 (P = 0.001). The US evaluation revealed a sensitivity of 100% (15 of 15) and a specificity of 50% (6 of 12). The average maximum SUV of the malignant lesions was greater than that of the benign lesions (4.12 ± 1.94 vs. 1.94 ± 0.82; P = 0.001). CONCLUSION: US evaluation of unexpected focal 18F-FDG uptakes on PET/CT scans can accurately distinguish benign lesions from malignant lesions.