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High Mammographic Density in Younger Women and Its Implications for Breast Cancer Subtypes
Sariningsih Hikmawati1,2, Kardinah2, Rizky Ifandriani Putri3
1Doctoral Program of Medical and Health Science, Faculty of Medicine, Public Health and Nursing, Universitas Gadjah Mada, Yogyakarta, Indonesia, ugm.ac.id.
Background:
High breast density is commonly observed in younger breast cancer patients (<45 years), and Asian women generally have dense breasts even beyond the age of 45 years. Its relationship with breast cancer subtypes and its profile remains unclear. This study is aimed at exploring the association between mammographic density and breast cancer molecular subtypes.
Methods:
A cross-sectional study evaluating mammographic density based on the 2013 BI-RADS classification among breast cancer patients at Dharmais Cancer Hospital between 2021 and 2023 was conducted. Clinicopathological variables-including histological subtype, tumor grade, ER, PR, HER2 status, Ki-67 index, and molecular subtypes by immunohistochemistry-were analyzed.
Results:
High breast density (BI-RADS C and D) was observed in 69% of patients, with Category C being the most common (57.1%). Invasive ductal carcinoma of no special type was the most prevalent and 47.2% of tumors were high grade. Most tumors were ER-negative (67.1%), PR-negative (59.6%), and HER2 0 (54.0%), with high Ki-67 index in 70.2% of cases. Age was associated with breast Density C and D and TNBC molecular subtype (p < 0.05). HER2, Ki-67, and molecular subtype were negatively correlated with ER (r = -0.217, r = -0.283, and r = -0.851, respectively; p < 0.05) and with PR (r = -0.169, r = -0.287, and r = -0.840, respectively; p < 0.05). Conversely, HER2 and Ki-67 expressions were positively correlated with more aggressive molecular subtypes (r = 0.307 and r = 0.354, respectively; p < 0.05).
Conclusion:
Younger breast cancer patients were associated with higher breast density and more aggressive tumor subtypes, which correlated with HER2 and Ki-67 expressions in breast cancer. These underscore the relevance of age-related biological factors in shaping breast cancer characteristics. However, among Indonesian women over 45 years old, the proportion of high breast density remains remarkably high (65.6%), suggesting that factors beyond age-such as genetic, hormonal, or lifestyle influences-may contribute to the persistence of dense breast tissue in this population.
