Mammographic Breast Density Patterns and Tumor Characteristics in Indian Women with Breast Cancer: A Retrospective Observational Study.

Background: Mammographic breast density (MBD) is a well-established risk factor for breast cancer and may also reflect underlying tumor biology. Data on MBD patterns and their association with tumor characteristics in Indian women remain limited.

Methods: This retrospective, case-only study included 500 women with pathologically proven primary breast cancer diagnosed between January 2022 and December 2023. Original digital mammograms were independently re-reviewed by experienced breast radiologists, and MBD was categorized according to ACR BI-RADS (A-D). Associations between MBD and age, tumor stage, nodal status, histologic grade, hormone receptor status, HER2/neu status, and Ki-67 index were evaluated using univariate analysis and multivariable logistic regression.

Results: Most patients were diagnosed between 41 and 60 years of age (median 50 years), and the majority exhibited ACR B or C breast density (93.2%). Mammographic density showed a significant inverse association with age. MBD was not independently associated with tumor stage, nodal status, estrogen or progesterone receptor status, or Ki-67 index. On, multivariate analysis, menopausal status independently predicted hormone receptor positivity (ER: OR 2.19, p < 0.001; PR: OR 1.72, p = 0.003). In contrast, dense breasts (ACR C/D) independently predicted high histologic grade (Grade III) (adjusted OR 1.72, p = 0.003). A univariate association between higher breast density and HER2/neu positivity was observed (p = 0.04) but was attenuated after multivariable adjustment.

Conclusion: In this Indian breast cancer cohort, mammographic density was more closely associated with aggressive tumor features than with stage or hormone receptor expression. These findings suggest that MBD may reflect tumor biology beyond tumor masking effects and provide a basis for larger, prospective, population-based studies.