Malignant breast masses detected only by ultrasound. A retrospective review.

BACKGROUND: The authors attempted to appraise the ability of high resolution, real-time ultrasound to find malignant breast masses that are nonpalpable and undetectable by high quality mammography in women with radiographically dense breasts, who were referred because of palpable or mammographically detected lesions.
METHODS: The records of breast ultrasound examinations of 12,706 women were retrospectively reviewed. All lesions were classified according to clinical and mammographic status as palpable or nonpalpable and as visible or nonvisible, respectively. Solid masses were sampled percutaneously by fine needle aspiration biopsy (FNAB) using ultrasound guidance and either were excised surgically or followed by sequential imaging.
RESULTS: There were 1575 solid masses detected sonographically that were nonpalpable and nonvisible by mammography; percutaneous biopsies (FNABs) were performed on 279 of these. Cytologic interpretation was definitely malignant in 22, suspicious in 18 (6 confirmed cancers), and benign in 183 (no false negatives). Surgery confirmed malignancy in 44 of the 1575 solid masses (2.8%), including 16 in patients with multifocal cancers.
CONCLUSIONS: Ultrasound can detect unsuspected, mammographically occult cancers in radiographically dense breasts and can alter treatment planning when a second cancer is found in a breast that otherwise was considered appropriate for conservative surgery. The authors recommend that any solid lesion detected incidentally during breast sonography either should be biopsied percutaneously under ultrasound guidance and/or closely followed with sequential scans.