Abstract 155: Density of breast lobules in benign breast tissue and association with future breast cancer risk.
Authors: Degnim Amy C. , Hartmann Lynn C. , Hoskin Tanya L. , Frost Marlene H. , Pankratz V Shane , Radisky Derek C. , Benetti Lorelle L. , Vachon Celine M. , Allers Teresa M. , Vierkant Robert A. , Visscher Daniel W. 
Published: August 2014

Abstract
Background: Women with benign breast disease (BBD) have increased breast cancer risk, and histologic features of the lesion stratify individual risk. We hypothesized that the concentration and type of terminal duct lobular units in BBD tissue is associated with future breast cancer risk.
Methods: A nested case-control series of 770 breast cancer cases and 1273 age- and year of biopsy-matched controls was identified within a cohort of 13,647 women with BBD from 1967-2001 (median follow-up 15.3 years). One representative H&E slide from each biopsy was reviewed by a single pathologist, who recorded total # of lobules present, and # of fibrocystic lobules (total and # with epithelial proliferation). Samples were also evaluated for lobular involution and primary BBD histology. Lobule density (LD) was calculated as # of lobules/cm2 in each tissue section. Breast cancer associations with LD's (total, fibrocystic, proliferative) were examined with conditional logistic regression. Odds ratios are reported per 1 SD increase in LD.
Results: Each LD measure was significantly associated with involution and primary BBD histology (p&lt;0.0001 for each). Fibrocystic (OR 1.17, 95% CI 1.06-1.28) and proliferative (OR 1.37, 95% CI 1.16-1.61) LD were each associated with case status (p≤0.001) but total LD did not reach significance (OR 1.09, 95% CI 1.0-1.20; p=0.06). LD associations were somewhat attenuated after adjusting for involution (total OR 1.04 p=0.41; fibrocystic OR 1.13 p=0.02; proliferative OR 1.28 p=0.002) and primary BBD histology (total OR 1.04 p=0.49; fibrocystic OR 1.08 p=0.15; proliferative OR 1.18 p=0.07).
Conclusions: The density of proliferative lobules in benign breast biopsy tissue is related to other BBD histologic features but may provide additional breast cancer risk stratification among women with proliferative BBD. Additional research will more fully evaluate the ability of this promising novel measure to predict breast cancer risk.
Lobule Density Measures (lobules per square cm) All values are Medians Total Lobule Density Fibrocystic Lobule Density Proliferative Lobule Density Overall 17.5 4.5 0.7 Cases 18.1 4.9 1.3 Controls 17.0 4.2 0.4 Primary BBD Histology Nonproliferative disease 16 3.3 0 Proliferative disease 18.6 5.8 2.7 Atypical hyperplasia 20.9 6.2 3.3 Involution Category None 28.7 5.3 1.0 Partial 19.0 5 1.2 Complete 8.5 2.1 0
Citation Format: Amy C. Degnim, Lynn C. Hartmann, Tanya L. Hoskin, Marlene H. Frost, V Shane Pankratz, Derek C. Radisky, Lorelle L. Benetti, Celine M. Vachon, Teresa M. Allers, Robert A. Vierkant, Daniel W. Visscher. Density of breast lobules in benign breast tissue and association with future breast cancer risk. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 155. doi:10.1158/1538-7445.AM2013-155