Optoacoustic Breast Imaging: Imaging-Pathology Correlation of Optoacoustic Features in Benign and Malignant Breast Masses

OBJECTIVE. Optoacoustic ultrasound breast imaging is a fused anatomic and functional modality that shows morphologic features, as well as hemoglobin amount and relative oxygenation within and around breast masses. The purpose of this study is to investigate the positive predictive value (PPV) of optoacoustic ultrasound features in benign and malignant masses. SUBJECTS AND METHODS. In this study, 92 masses assessed as BI-RADS category 3, 4, or 5 in 94 subjects were imaged with optoacoustic ultrasound. Each mass was scored by seven blinded independent readers according to three internal features in the tumor interior and two external features in its boundary zone and periphery. Mean and median optoacoustic ultrasound scores were compared with histologic findings for biopsied masses and nonbiopsied BI-RADS category 3 masses, which were considered benign if they were stable at 12-month follow-up. Statistical significance was analyzed using a two-sided Wilcoxon rank sum test with a 0.05 significance level. RESULTS. Mean and median optoacoustic ultrasound scores for all individual internal and external features, as well as summed scores, were higher for malignant masses than for benign masses (p < 0.0001). High external scores, indicating increased hemoglobin and deoxygenation and abnormal vessel morphologic features in the tumor boundary zone and periphery, better distinguished benign from malignant masses than did high internal scores reflecting increased hemoglobin and deoxygenation within the tumor interior. CONCLUSION. High optoacoustic ultrasound scores, particularly those based on external features in the boundary zone and periphery of breast masses, have high PPVs for malignancy and, conversely, low optoacoustic ultrasound scores have low PPV for malignancy. The functional component of optoacoustic ultrasound may help to overcome some of the limitations of morphologic overlap in the distinction of benign and malignant masses.