The effectiveness of MR imaging in the assessment of invasive lobular carcinoma of the breast.

Invasive lobular carcinoma (ILC) of the breast is, due to its diffuse infiltrative growth pattern, a diagnostic challenge. Even in retrospect, only up to 80% are visible at mammography. Moreover, both mammography and ultrasound tend to structurally underestimate the size of ILC. Breast magnetic resonance (MR) imaging is usually performed after initial cancer detection. In this setting, the sensitivity is approximately 96%. However, multiple cases have been reported in which ILC has been initially detected with MR imaging, thus implying a potential advantage of MR imaging over mammography in screening. The size of an ILC as reported on MR imaging correlates well with size at pathology (r = 0.89). Additional tumor foci are detected by MR imaging in approximately one-third of patients, and these foci are subsequently pathologically confirmed in 88%. Hence, preoperative MR imaging of ILC changes management in 28% of patients, often appropriately. Nevertheless, it is still essential to obtain histology prior to large changes in the therapeutic regime based on MR imaging findings, either by second-look ultrasound or by MR imaging-guided biopsy. Using this approach, it has been shown that preoperative MR imaging reduces the rate of reexcisions after breast-conserving surgery from 27% to 9%, without increasing the rate of mastectomies and without extending total therapy time. Finally, the early detection of contralateral carcinomas only visible at MR imaging in approximately 7% of patients with ILC implies that preoperative MR imaging in these patients improves survival, although the magnitude of this effect is unknown.