[Correlation between breast density and age, breast cancer molecular subtype]

Objective: To explore the correlation between breast density and breast cancer molecular subtype. Methods: The data of 1 407 cases of breast cancer immunohistochemistry and preoperative mammography in Tianjin Medical University Cancer Institute and Hospital from August 2015 to August 2016 were retrospectively analyzed. All cases were divided into four groups: <45 years old, 45-54 years old, 55-64 years old and ≥ 65 years old, and all groups were divided into four molecular subtypes: Luminal A, Luminal B, HER2-enriched and triple-negative according to immunohistochemical results. Person correlation test was used to analyze the correlation between breast density and age; Kruskal-Wallis test was used to analyze the difference in breast density between different molecular subtypes. Results: There was a negative correlation between breast density and age (r=-0.55, P<0.01). Descriptive analysis results showed that the mean breast density of<45 years old, 45-54 years old, 55-64 years old and ≥65 years old was 20.0%±7.3%, 16.2%±8.4%, 10.5%±5.2%, and 7.9%±3.2%, respectively. The mean breast density of Luminal A, Luminal B, HER2-enriched and triple-negative was 14.0%±8.1%, 14.5%±7.6%, 14.8%±7.7% and 13.2%±7.3%, respectively. Kruskal-Wallis test showed significant statistical differences in breast density among molecular subtypes in the group of<45 years old (P<0.05), while no statistical significance in other groups (all P>0.05). Conclusion: There is correlation between breast density and breast cancer molecular subtype in young patients, but whether breast density has a potential evaluation effect on breast cancer molecular subtype still needs to be further studied.