Occult cancer in women with dense breasts: detection with screening US--diagnostic yield and tumor characteristics.

PURPOSE: To evaluate bilateral screening ultrasound (US) in the detection of otherwise occult masses and cancer in women with dense breasts and normal mammographic and physical examination findings. MATERIALS AND METHODS: Of 11,220 consecutive patients prospectively examined, all 3,626 women with dense breasts and normal mammographic and physical examination findings underwent physician-performed screening US. The size and stage of cancers detected with US alone were compared with those of cancers detected on mammograms, at physical examination, or both, in the remainder of the patients. RESULTS: In the group of 3,626 women, 11 surgically proved cancers in 11 women (prevalence, 0.30%) were identified with US alone. These cancers were not statistically significantly different in mean surgical size and stage from those of 61 nonpalpable, mammographically detected cancers and were smaller and lower in stage than 64 palpable cancers (P < .01) that were diagnosed in the remainder of the population. In the women with dense breasts, overall cancer detection increased by 17% (from 63 to 74 tumors), and the number of tumors detected only with imaging increased by 37% (from 30 to 41 tumors). CONCLUSION: Screening US can depict small, early-stage, otherwise occult cancers similar in size and stage to mammographically identified nonpalpable cancers and smaller and lower in stage than palpable cancers in dense breasts.