Burcu GÜMÜŞTEKİN, Emre TEKE
Southern Clinics of Istanbul Eurasia - 2026;37(3):230-238
Objective: Mammographic subcutaneous fat thickness (SFT) has been proposed as a spatially specific surrogate of locoregional adiposity in breast cancer research. This study aimed to evaluate the relationship between mammographically measured SFT and molecular subtypes, Ki-67 proliferation index, hormone receptor expression, and key clinicopathological parameters in patients with invasive ductal carcinoma (IDC). Methods: This retrospective, cross-sectional, single-center study included 180 female patients who underwent surgical treatment for IDC between October 2023 and January 2026. SFT was measured from standard mammographic images. Molecular subtype classification followed the St. Gallen 2013 Consensus criteria. Statistical analyses included Spearman correlation, Kruskal-Wallis and Mann-Whitney U tests, multivariable linear regression, and receiver operating characteristic (ROC) curve analysis. Results: SFT showed no statistically significant correlation with Ki-67 (rho=0.127, p=0.089), tumor size, age, estrogen receptor (ER) percentage, or progesterone receptor (PR) percentage. SFT did not differ significantly across molecular subtypes, BI-RADS density categories, histological grade, or lymph node status. In multivariable linear regression, body mass index (BMI) was the sole independent predictor of SFT (beta=0.331, p<0.001; R²=0.110). BMI differed significantly across molecular subtypes (p=0.024), with the triple-negative (TN) subtype associated with significantly higher BMI than both Luminal A (p=0.021) and Luminal B (p=0.004). A statistically significant linear trend was identified between increasing BI-RADS density category and tumor biological aggressiveness (linear-by-linear association, p=0.046). The area under the ROC curve (AUC) for SFT in predicting Ki-67>=20% was 0.590 (95% CI: 0.458-0.721, p=0.192), and for BMI was 0.417 (95% CI: 0.287-0.547, p=0.227); neither reached statistical significance. Conclusions: In IDC, mammographic SFT reflects systemic adiposity rather than tumor biology and lacks clinically meaningful discriminatory power as an independent imaging biomarker. The association between the triple-negative subtype and higher BMI supports the role of systemic adiposity in subtype-specific tumor biology.
