BMI and Breast Subcutaneous Fat: Potential Indicators for Ultrasound Diagnosis of Breast Cancer?

Obesity is closely associated with the occurrence and progression of breast cancer. While body mass index (BMI) is widely used to diagnose obesity, it has certain limitations. Subcutaneous fat thickness (SFT) also serves as an indicator of body composition. However, studies on breast SFT are scarce. This study aims to investigate the relationship between BMI, breast SFT, and ultrasound features of breast cancer, as well as their associations with tumor proliferation and invasiveness.

This study retrospectively analyzed the relationship between BMI and clinical and ultrasound characteristics in 1670 patients. Among them, breast SFT was measured in 470 patients using mammography and ultrasound, and the correlation between SFT and BMI was assessed. The relationship between ultrasound-measured SFT and pathological as well as ultrasound features was also analyzed. The correlation between breast SFT, BMI, and somatic gene mutations was analyzed in 234 patients.

Patients with BMI ≥24 kg/m² exhibited more malignant ultrasound features. SFT measured by mammography was correlated with SFT measured by ultrasound (r = 0.565, p < .001). Both BMI and SFT measured via mammography (r = 0.578, p < .001) and ultrasound (r = 0.485, p < .001) showed significant correlations. Breast SFT varied significantly among tumors with different shapes (p = .025), boundaries (p < .001), and posterior echo features (p < .001). The area under the curve (AUC) for breast SFT predicting irregular shape, halo, and posterior shadowing was 0.605, 0.666, and 0.632, respectively, with cutoff values of 8.65, 8.35, and 8.35 mm. Patients with breast SFT ≥8.6 mm demonstrated significantly elevated Ki67 levels (p = .004). No differences in somatic mutation frequencies were found at a threshold of 8.60 mm for fat thickness or at a BMI of 24 kg/m². However, at BMI ≥22 kg/m², mutation frequencies were higher.

BMI and breast SFT are associated with malignant ultrasound features. While both have diagnostic value, BMI is more reliable than fat thickness for predicting cancer proliferation and invasion, with a BMI threshold of 22 kg/m² offering higher diagnostic value than 24 kg/m².