Background parenchymal enhancement (breast MRI)
Background parenchymal enhancement on breast MRI refers to the normal contrast enhancement of fibroglandular tissue.
Background parenchymal enhancement is more common in younger patients with dense breasts 1,8. Reflecting hormonal influence, background enhancement is decreased after menopause 2.
Background parenchymal enhancement is depicted on T1 weighted images with fat suppression. Subtraction maximal intensity projections can be helpful.
Background enhancement usually appears as a homogeneous or stippled area (multiple tiny dots separated by nonenhancing parenchyma), in a bilateral diffuse or regional distribution. Due to preferential vascular supply, greater enhancement is seen in the upper outer quadrant and along the inferior aspect of the breast 1.
The level of background enhancement is assessed on the first postcontrast acquisition, at approximately 90 seconds. On delayed images, background enhancement is persistent (progressive/increased in intensity compared to the first postcontrast phase).
The BI-RADS lexicon provides standard descriptors for the level and symmetry of background parenchymal enhancement 1:
- level (evaluated relative to the amount of fibroglandular tissue and not total breast volume)
- symmetric (equal in both breasts)
- suggestive of normal, benign background parenchymal enhancement
- asymmetric (more prominent in one breast than the other)
- symmetric (equal in both breasts)
Treatment and prognosis
Because background enhancement is more prominent during the luteal phase of the menstrual cycle, elective breast MRI should be scheduled at days 7-14 during the follicular phase of a woman's cycle.
As it may be confused for suspicious lesions, increased background parenchymal enhancement increases the rate of abnormal interpretations (BI-RADS category 0, 3, 4, or 5 assessments) but does not decrease the sensitivity and cancer detection rate 3,4.
Increased background parenchymal enhancement is an imaging biomarker of higher risk of breast cancer, independent of the amount of fibroglandular tissue, in women at high risk 5,6,10. In patients who undergo adjuvant endocrine therapy, high background parenchymal enhancement in the nonaffected breast predicts poorer cancer outcomes 7. Similarly, in the setting of neoadjuvant chemotherapy, reduction in level of background parenchymal enhancement correlates with pathological tumor response 9.
A larger area of background parenchymal enhancement overlaps in appearance with a focal area of nonmass enhancement, which requires further assessment and management 10.
- 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. King V, Gu Y, Kaplan JB, Brooks JD, Pike MC, Morris EA. Impact of menopausal status on background parenchymal enhancement and fibroglandular tissue on breast MRI. (2012) European radiology. 22 (12): 2641-7. doi:10.1007/s00330-012-2553-8 - Pubmed
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- 5. King V, Brooks JD, Bernstein JL, Reiner AS, Pike MC, Morris EA. Background parenchymal enhancement at breast MR imaging and breast cancer risk. (2011) Radiology. 260 (1): 50-60. doi:10.1148/radiol.11102156 - Pubmed
- 6. Dontchos BN, Rahbar H, Partridge SC, Korde LA, Lam DL, Scheel JR, Peacock S, Lehman CD. Are Qualitative Assessments of Background Parenchymal Enhancement, Amount of Fibroglandular Tissue on MR Images, and Mammographic Density Associated with Breast Cancer Risk?. (2015) Radiology. 276 (2): 371-80. doi:10.1148/radiol.2015142304 - Pubmed
- 7. van der Velden BH, Dmitriev I, Loo CE, Pijnappel RM, Gilhuijs KG. Association between Parenchymal Enhancement of the Contralateral Breast in Dynamic Contrast-enhanced MR Imaging and Outcome of Patients with Unilateral Invasive Breast Cancer. (2015) Radiology. 276 (3): 675-85. doi:10.1148/radiol.15142192 - Pubmed
- 8. Uematsu T, Kasami M, Watanabe J. Should breast MRI be performed with adjustment for the phase in patients' menstrual cycle? Correlation between mammographic density, age, and background enhancement on breast MRI without adjusting for the phase in patients' menstrual cycle. (2012) European journal of radiology. 81 (7): 1539-42. doi:10.1016/j.ejrad.2011.04.059 - Pubmed
- 9. Oh SJ, Chae EY, Cha JH, Shin HJ, Choi WJ, Kim HH. Relationship between background parenchymal enhancement on breast MRI and pathological tumor response in breast cancer patients receiving neoadjuvant chemotherapy. (2018) The British journal of radiology. 91 (1088): 20170550. doi:10.1259/bjr.20170550 - Pubmed
- 10. Giess CS, Yeh ED, Raza S, Birdwell RL. Background parenchymal enhancement at breast MR imaging: normal patterns, diagnostic challenges, and potential for false-positive and false-negative interpretation. (2014) Radiographics : a review publication of the Radiological Society of North America, Inc. 34 (1): 234-47. doi:10.1148/rg.341135034 - Pubmed
- 11. Thompson CM, Mallawaarachchi I, Dwivedi DK, Ayyappan AP, Shokar NK, Lakshmanaswamy R, Dwivedi AK. The Association of Background Parenchymal Enhancement at Breast MRI with Breast Cancer: A Systematic Review and Meta-Analysis. (2019) Radiology. 292 (3): 552-561. doi:10.1148/radiol.2019182441 - Pubmed