RESUMO
BACKGROUND: PET-CT is widely used for evaluation and follow-up of malignancy. Incidental hypermetabolic lesions are often found on PET-CT, some of which are confirmed to be malignant. PURPOSE: To estimate the role of combined Breast Imaging-Reporting and Data System (BI-RADS) assessment using mammography and sonography for evaluation of incidental hypermetabolic lesions on 18F-FDG PET-CT and to determine an appropriate next step. MATERIAL AND METHODS: This study included incidental hypermetabolic lesions found in the breasts of 7594 women who underwent PET-CT at three university-affiliated hospitals between January 2006 and December 2011. We reviewed the maximum standardized uptake value (SUVmax) of incidental lesions, combined BI-RADS assessment of mammography and sonography, and final results. We analyzed the negative predictive values of the probably benign (categories 1-3) group and the sensitivity of suspicious (categories 4 and 5) groups according to combined BI-RADS assessment. RESULTS: Forty-three patients (0.6%) had 49 incidental hypermetabolic lesions in the breast. Histologic diagnosis in 17 patients confirmed nine breast cancers (27.3%). Sixteen patients underwent imaging follow-up for at least 2 years; no breast cancer was detected. Thirteen patients were lost to follow-up and were excluded. For the suspicious (n = 14) and probably benign (n = 19) groups according to combined BI-RADS assessment, both the sensitivity and negative predictive values were 100%. Using an optimal diagnostic cut-off value of 2.15, the malignancy rate was not significantly different (16.7% vs. 45.5%, respectively, in the group with SUVmax < 2.15 and the group with SUVmax ≥ 2.15; P > 0.05). The SUVmax of the confirmed malignant and assumed benign groups were not significantly different (3.1% vs. 2.2%, respectively; P > 0.05). CONCLUSION: Both mammography and sonography should be considered the next step to evaluate incidental hypermetabolic lesions on 18F-FDG PET-CT because combined BI-RADS assessment provides an excellent negative predictive value for excluding malignancy.