Sonography of the breast: controversies and opinions.

Abstract

S onography of the breast today has many similarities to mammography 10-15 years ago [1]. These similarities include a rapid increase in usage, with the number of sonographic examinations of the breast performed in my own department having more than doubled in each of the last 4 years. Breast sonography, like early mammography, has controversial mdications and limited cost-benefit data, and its popularity has outstripped formal training and expertise in performing and interpreting the examination. Finally, breast sonography today, like earlier screening mammography, is underused. This paper discusses and opines about many of the controversies surrounding sonography of the breast. Sonography of the breast was initially used to assess whether a palpable mass was cystic or solid, often as an alternative to bedside needle aspiration. The evolution of sonographic equipment led to expanded indications, including the assessment of impalpable masses identified by mammography. Today, sonography of the breast is frequently preferred to mammographic techniques for directing aspirations, wire localizations, and core biopsies. Indeed, I believe that the relative ease of performing core biopsies under sonographic guidance has resulted in too many biopsies of impalpable probably benign breast nodules in category 3 of the Breast Imaging Reporting and Data System (BI-RADS) [2], which have a less than 2% chance of malignancy and traditionally would have undergone 6-month mammographic follow-up [3]. Whether one should use sonography to help differentiate a benign from a malignant solid breast mass is one of the major controversies in breast imaging. This is particularly true regarding impalpable masses because palpable solid masses are often removed regardless of their imaging characteristics. Stavros et al. [4] described the sonographic evaluation of 750 palpable and impalpable solid breast nodules, all of which had subsequent histologic confirmation. These authors reported a 99.5% (424/426) negative predictive value for cancer in those nodules with benign sonographic characteristics. This predictive value for benignity is higher than that of a lesion in the probably benign mammographic category 3 Breast Imaging Reporting and Data System [2], for which a 6-month follow-up is a well-accepted recommendation [3]. These findings suggest that followup of a solid but sonographically benign breast mass is a reasonable alternative to biopsy. Stavros et al. have been criticized for inclusion of masses that, by conventional mammographic criteria, should not have undergone biopsy [5]. This criticism is not applicable to a more recent multiinstitutional trial (Taylor KJW et al., unpublished data) that confirms many of the findings of Stavros et al. The study by Taylor et al. incorporated Doppler techniques that might assist in the diagnosis of malignancy by quantifying blood flow within solid lesions. I concur with the findings of Stavros et al. and Taylor et al., and my department relies heavily on sonographic appearances in deciding whether to recommend follow-up rather than biopsy of probably benign solid breast masses identifled by mammography. Unfortunately, despite discussions (Mendelson EB, personal communication), no consensus or recommendations have been reached by the multispecialty Women’s Imaging Consensus Panel of the American College of Radiology Task Force on Appropriateness Criteria [6]. Not all palpatory abnormalities in the breast are discrete masses, and an equivocal abnormality is commonly palpated. In such instances breast sonography can confirm and, perhaps more important, usually provide strong negative reassurance that no actual mass exists in the area of palpatory concern. This reassurance can rarely be provided by normal mammographic findings, and I heartily endorse the use of sonography in women with equivocal breast examinations. Unfortunately, in my experience many of these referrals are for vague “nebulomas,” which at the time of the sonographic examination cannot be palpated by the technologist, the radiologist, or even the patient. This observation reflects the fact that younger women who palpate a suspected mass on self-examination are frequently referred directly for sonography, and sometimes mammography, before being examined by their primary physician, by a surgeon, or by both. Breast imaging before clinical examination is controversial, but I