Lobule type and subsequent breast cancer risk: Results from the Nurses' Health Studies

Abstract

Lobules in normal breast tissue can be classified based on their degree of development, which may affect their susceptibility to carcinogenesis. However, few epidemiologic studies to date have addressed this. The authors examined the association between lobule type and subsequent breast cancer risk in a nested case-control study of benign breast disease (BBD) and breast cancer within the Nurses' Health Studies (200 cases, 915 controls). Benign breast biopsy slides were reviewed by pathologists, and normal terminal duct lobular units were classified as having no type 1 lobules, mixed lobule types, or predominant type 1 and no type 3 lobules. Logistic regression was used to compute odds ratios (ORs) and 95% confidence intervals (CIs) for the association between lobule type and breast cancer risk. Women with predominant type 1 and no type 3 lobules (54 cases, 321 controls) had a decreased risk of breast cancer compared with those with no type 1 lobules or mixed lobule types (OR=0.63; 95% CI, 0.44-0.91), although this was attenuated after adjustment for histologic category of BBD (OR=0.71; 95% CI, 0.49-1.02). Having predominant type 1 lobules and no type 3 lobules was associated with a similar risk reduction for all categories of BBD (nonproliferative: OR=0.73 [95% CI, 0.36-1.50]; proliferative without atypia: OR=0.80 [95% CI, 0.47-1.35]; and atypical hyperplasia: OR=0.61 [95% CI, 0.28-1.35]). These results provided preliminary evidence that lobule type may be an important marker of breast cancer risk in women with BBD.