Benign versus malignant solid breast masses: US differentiation

PURPOSE: To investigate the general applicability and interobserver variabi lity of ultrasonographic (US) features in differentiating benign from malig nant solid breast masses. MATERIALS AND METHODS: One hundred sixty-two consecutive solid masses with a tissue diagnosis were reviewed. Three radiologists reviewed the masses wi thout knowledge of clinical history or histologic examination results. RESULTS: US features that most reliably characterize masses as benign were a round or oval shape (67 of 71 [94%] were benign), circumscribed margins ( 95 of 104 [91%] were benign), and a width-to-anteroposterior (AP) dimension ratio greater than 1.4 (82 of 92 [89%] were benign). Features that charact erize masses as malignant included irregular shape (19 of 31 [61%] were mal ignant), microlobulated (four of six [67%] were malignant) or spiculated (t wo of three [67%] were malignant;) margins, and width-to-AP dimension ratio of 1.4 or less (28 of 70 [40%] were malignant). If the three most reliable criteria had been strictly applied by each radiologist, the overall cancer biopsy yield would have increased (from 23% to 39%) by 16%. When US images and mammograms were available, the increase in biopsy yield contributed by US was not statistically significant (2%, P = .73). However, in independen t reviews, one to three reviewers interpreted four carcinomas as benign at US. CONCLUSION: The data confirm that certain US features can help differentiat e benign from malignant masses. However, practice and interpreter variabili ty should be further explored before these criteria are generally applied t o defer biopsy of solid masses.