Sonographic evaluation of solid breast nodules

Because of the heterogeneity of breast cancer from nodule to nodule, single findings cannot achieve the sensitivity or the negative predictive value necessary to identify a low-risk group that can be offered the option of follow-up (ACR Breast Imaging Reporting and Data System [BIRADS] 3 group). However, by using multiple findings in a strict algorithm, such a group can be identified. It is also important to keep in mind that breast cancer can be heterogeneous within an individual nodule. Part of the nodule may have circumscribed features that simulate a benign lesion, while another part may be spiculated and obviously malignant. Only by scanning the whole surface and substance of the nodule in two orthogonal planes (radial and anti-radial) can the presence of suspicious findings be excluded, and if there is a mixture of benign and suspicious findings, the benign findings should be ignored.

These studies show that sonography is useful in the characterization of solid breast masses. Characterizing solid breast nodules into BIRADS categories defines carcinomas that might have been missed clinically or mammographically. It identifies a BIRADS 3 group that has far less than 2% risk of being malignant and can offer the patient the option of follow-up rather than biopsy. Currently, approximately 80% of patients with BIRADS 3 solid nodules are electing to be followed rather than to undergo biopsy. It improves the accuracy of the diagnosis of malignant breast lesions. Importantly, it also accurately defines a population of benign solid breast lesions that do not require biopsy when strict sonographic criteria of benignity are present.

To achieve the desired sensitivity and negative predictive values of 98% or greater the algorithm must be strictly adhered to. When the patient elects to be followed rather than undergo biopsy, follow-up should be performed in 6 months, not 1 year. The malignant lesions at most risk to be mischaracterized as BIRADS 3 are higher grade invasive ductal carcinomas that grow rapidly enough for change to be readily detected at 6 months.

Table 1 Current study: characterization of solid breast nodules

Table 2 Prospective characterization of 1211 solid nodules into BIRADS categories (all 1211 nodules have undergone biopsy)