Sonographic criteria for differentiation of benign and malignant solid breast lesions: size is of value.

PURPOSE: The purpose of this study was to evaluate whether lesion size may influence the value of sonographic findings in the differential diagnosis between benign or malignant breast lesions.
MATERIALS AND METHODS: Sonographic features of 256 histologically confirmed (148 benign, 108 malignant) breast lesions were retrospectively and independently reviewed by three radiologists unaware of mammographic findings and pathology results. Each lesion was assessed for several sonographic features and assigned a level of suspicion. Logistic modelling defined the predictive value of each sonographic feature per se and in relation to lesion size. The k statistic (k) evaluated interobserver agreement in lesion classification. The accuracy of breast sonography in characterising solid lesions was also evaluated.
RESULTS: Analysis of the sonographic features predictive of malignant disease, taken as a whole, showed that only irregular margins and marked hypoechogenicity maintain their predictive value independent of lesion size. When lesion size is considered, the other features remain significant only for lesions larger than 7 mm. Interobserver agreement for sonographic suspicion, when calculated not taking into account lesion size, was good or excellent whereas it was reduced for lesions smaller than 7 mm. Accuracy of breast sonography improved when evaluating lesions larger than 7 mm.
CONCLUSIONS: Lesion size influences the value of sonographic findings in distinguishing benign from malignant lesions. The usually adopted criteria in sonography have a significantly lower accuracy in characterisation of small lesions.