Nonmass Enhancement in Breast MRI

According to the Breast Imaging and Reporting Data System (BI-RADS), one of the main challenges of MRI is diagnosing the non- mass enhancement (NME).A wide variety of benign and malignant processes can manifest as non-mass enhancement, which is defined as an area of enhancement that does not meet criteria for a mass, such as having nonconvex borders or intervening fat or fibroglandular tissue between the enhancing components. The BI-RADS lexicon provides standard descriptors for the distributionof NME including; Focal, linear, segmental, regional, multiple regions and diffuseand also for internal pattern of non-mass enhancementas homogeneous, hetereogenous, clumped and clustered ring pattern. Non-mass enhancement is usually assessed as suspicious and managed with core needle biopsy (BI-RADS 4). Second-look breast ultrasound is helpful to look for a correlate that can be targeted for ultrasound-guided rather than MRI-guided breast biopsy. There are limited data supporting a probably benign assessment for certain types of non-mass enhancement (BI-RADS 3). Anecdotal experience suggests homogeneous non-mass enhancement in a focal, regional, or multiple regions distribution on baseline examination may fit this category. In some clinical situations, enhancement could be transient and related to hormonal status. For instance, a premenopausal patient may be scanned in a suboptimal part of her cycle, or a postmenopausal patient may be taking hormone replacement therapy. If this is suspected but the finding is not clearly background parenchymal enhancement, the non-mass enhancement may be assessed as probably benign (BI-RADS 3) with a recommendation for a very short interval follow up (2-3 months), timed for week 2 of the patient›s cycle or after suspending hormonal therapy .