Non-mass enhancement at breast MRI is defined in the BI-RADS lexicon as an area of enhancement that does not meet criteria for a mass, such as by having nonconvex borders or intervening fat or fibroglandular tissue between the enhancing components.
A wide variety of benign, high risk and malignant processes can manifest as non-mass enhancement 2,6:
- fibrocystic changes
- pseudoangiomatous stromal hyperplasia (PASH)
- apocrine metaplasia
- radiation therapy effect
- flat epithelial atypia
- atypical ductal hyperplasia
- radial scar/complex sclerosing lesion
- intraductal papilloma
- ductal carcinoma in situ
- invasive carcinoma of no special type (ductal carcinoma not otherwise specified)
- invasive lobular carcinoma
The BI-RADS lexicon (5th edition) provides standard descriptors for the distribution and internal pattern of non-mass contrast enhancement 1.
- focal: confined area less than a breast quadrant characterized by a non-mass internal enhancement pattern
- linear: straight, curved, or branching arrangement of enhancement, suggestive of ductal or periductal involvement
- segmental: triangular or conical arrangement with the apex directed toward the nipple, suggestive of ductal or periductal involvement
- regional: area larger than a breast quadrant
- multiple regions: more than one large area, separated by normal tissue, not conforming to a ductal distribution (patchy)
- diffuse: randomly arranged throughout the breast
- internal enhancement patterns
- homogeneous: confluent and uniform
- heterogeneous: randomly separated by normal tissue in a nonuniform pattern
- clumped: small aggregates of enhancement ("cobblestone" like) in various sizes and shapes, suggestive of ductal involvement; used in combination with focal, linear, segmental, or regional distribution
- clustered ring: multiple small ring shapes closely arranged, suggestive of periductal involvement
Treatment and prognosis
In general, a substantial minority of non-mass enhancement proves to be malignant 3-5. Second-look breast ultrasound is prudent to look for a correlate that can be targeted for ultrasound-guided rather than MRI-guided breast biopsy.
Alternative considerations for describing an enhancing area depends on the size, shape, and distinctness from the rest of the breast parenchyma:
Non-mass enhancement is usually assessed as suspicious and managed with core needle biopsy (BI-RADS 4).
There are limited data supporting a probably benign assessment for certain types of non-mass enhancement (BI-RADS 3), which remains a matter of intuition for most radiologists 1. In one newer study, a linear distribution of non-mass enhancement <1 cm that is not branching is probably benign 7. Anecdotal experience suggests homogeneous non-mass enhancement in a focal, regional, or multiple regions distribution on baseline examination may also fit this category 8,9.
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 1.
- 1. D’Orsi CJ, Sickles EA, Mendelson EB, Morris EA, et al. ACR BI-RADS® Atlas, Breast Imaging Reporting and Data System. Reston, VA, American College of Radiology; 2013. ISBN:155903016X. Read it at Google Books - Find it at Amazon
- 2. Chadashvili T, Ghosh E, Fein-Zachary V, Mehta TS, Venkataraman S, Dialani V, Slanetz PJ. Nonmass enhancement on breast MRI: review of patterns with radiologic-pathologic correlation and discussion of management. (2015) AJR. American journal of roentgenology. 204 (1): 219-27. doi:10.2214/AJR.14.12656 - Pubmed
- 3. Chikarmane SA, Michaels AY, Giess CS. Revisiting Nonmass Enhancement in Breast MRI: Analysis of Outcomes and Follow-Up Using the Updated BI-RADS Atlas. (2017) AJR. American journal of roentgenology. 209 (5): 1178-1184. doi:10.2214/AJR.17.18086 - Pubmed
- 4. Chikarmane SA, Birdwell RL, Poole PS, Sippo DA, Giess CS. Characteristics, Malignancy Rate, and Follow-up of BI-RADS Category 3 Lesions Identified at Breast MR Imaging: Implications for MR Image Interpretation and Management. (2016) Radiology. 280 (3): 707-15. doi:10.1148/radiol.2016151548 - Pubmed
- 5. Gutierrez RL, DeMartini WB, Eby PR, Kurland BF, Peacock S, Lehman CD. BI-RADS lesion characteristics predict likelihood of malignancy in breast MRI for masses but not for nonmasslike enhancement. (2009) AJR. American journal of roentgenology. 193 (4): 994-1000. doi:10.2214/AJR.08.1983 - Pubmed
- 6. Shimauchi A, Ota H, Machida Y, Yoshida T, Satani N, Mori N, Takase K, Tozaki M. Morphology evaluation of nonmass enhancement on breast MRI: Effect of a three-step interpretation model for readers' performances and biopsy recommendations. (2016) European journal of radiology. 85 (2): 480-8. doi:10.1016/j.ejrad.2015.11.043 - Pubmed
- 7. Machida Y, Tozaki M, Shimauchi A, Yoshida T. Two Distinct Types of Linear Distribution in Nonmass Enhancement at Breast MR Imaging: Difference in Positive Predictive Value between Linear and Branching Patterns. (2015) Radiology. 276 (3): 686-94. doi:10.1148/radiol.2015141775 - Pubmed
- 8. Spick C, Szolar DH, Baltzer PA, Tillich M, Reittner P, Preidler KW, Pinker-Domenig K, Helbich TH. Rate of malignancy in MRI-detected probably benign (BI-RADS 3) lesions. (2014) AJR. American journal of roentgenology. 202 (3): 684-9. doi:10.2214/AJR.13.10928 - Pubmed
- 9. Lee KA, Talati N, Oudsema R, Steinberger S, Margolies LR. BI-RADS 3: Current and Future Use of Probably Benign. (2018) Current radiology reports. 6 (2): 5. doi:10.1007/s40134-018-0266-8 - Pubmed