Abstract P6-10-14: Association between mammographic breast density and histologic features of benign breast disease
Authors: Ghosh Karthik , Vierkant Robert A , Frank Ryan D , Visscher Daniel W , Pankratz Vernon S , Scott Christopher G , Radisky Derek C , Frost Marlene H , Hartmann Lynn C , Degnim Amy C , Vachon Celine M 
Published: May 2015

Abstract
Background: Mammographic breast density (MBD) reflects the proportion of fibroglandular tissue in the breast, and is an established risk factor for breast cancer. Benign breast disease (BBD) is also a known risk factor for breast cancer. We previously showed an association between lobular involution (physiologic atrophy) and MBD in a large cohort study of women with BBD. We performed a comprehensive evaluation of the association of histologic features of BBD with MBD. Methods: The Mayo BBD cohort includes women, 18 to 85 years, who were diagnosed with BBD at Mayo Clinic in Rochester, MN between 01/01/1967 and 12/31/1991. For this study, we included women who had a mammogram within 6 months of BBD diagnosis, and diagnosed with BBD between 1985 and 1991 when parenchymal pattern of breast density was clinically recorded. Risk factor information such as age, and body mass index (BMI) was collected from medical records. Parenchymal pattern, assessed clinically and previously used in multiple studies of MBD and risk, classified breast density based on extent and type of density, into four categories: N1 (non-dense, no ducts visible); P1 (ductal prominence occupying &lt;25% breast); P2 (prominent ductal pattern occupying &gt;25% of the breast; DY (homogenous plaque-like areas of density). All assessments of benign breast tissue were performed by expert breast pathologists blinded to both MBD and BBD reports. Histologic characteristics included overall impression (non-proliferative disease (NPD), proliferative disease without atypia (PDWA), and atypical hyperplasia (AH)), proportion of normal lobules that were involuted (no (0%), partial (1 to 74%), or complete (≥75%)), type of AH (ADH or ALH), ductal and lobular hyperplasia, calcifications, sclerosing adenosis, columnar alteration, cyst, fibroadenoma, marked fibrosis, intra-ductal papilloma, radial scar (number and size), duct ectasia, and mucocele like tumors. Associations of parenchymal pattern with BBD characteristics were examined using multicategorical nominal logistic regression models. We first examined associations after adjustment for age and BMI. All variables statistically significant (p&lt;0.05) in these models were then simultaneously included in a fully-adjusted model. Results: Of 2,257 women in the study, 14% were &lt;40 years old, 52.7% between 40- 59 years, and 32.9% were ≥60 years. In this sample, 55.2% of women had NPD, 36% had PDWA, and AH in 8.8%. MBD was classified as N1 in 21.8%, P1 in 12.6%, P2 in 23.7% and DY in 41.9%. Age- and BMI-adjusted analyses showed that there was an association of parenchymal pattern with overall impression, lobular involution, ductal hyperplasia, sclerosing adenosis, columnar alteration, cyst, duct ectasia and fibrosis. Multivariate analyses found that women of younger age (p&lt;0.001) and with lower BMI (p&lt;0.001), presence of fibrosis (p&lt;0.001) and no involution (p=0.016) were more likely to have P2 or DY parenchymal pattern than women without those characteristics. Conclusion: Among women with benign breast disease, higher MBD is associated with younger age, lower BMI, fibrosis, and lack of lobular involution. These findings, concordant with other studies of MBD, provide insight into underlying mechanisms by which MBD and BBD contribute to breast cancer risk.
Citation Format: Karthik Ghosh, Robert A Vierkant, Ryan D Frank, Daniel W Visscher, Vernon S Pankratz, Christopher G Scott, Derek C Radisky, Marlene H Frost, Lynn C Hartmann, Amy C Degnim, Celine M Vachon. Association between mammographic breast density and histologic features of benign breast disease [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P6-10-14.