Quantitative MRI morphology of invasive breast cancer: correlation with immunohistochemical biomarkers and subtypes.

Background: Breast cancer is a heterogeneous disease with intrinsic molecular subtypes. The different biology and histology of breast cancer exhibit different tumor morphology at breast magnetic resonance imaging (MRI). However, few studies have examined the quantitative relationship between the MRI morphological and immunohistochemical features in breast cancer.

Objective: To investigate the correlations between tumor roundness, as quantitatively assessed with MRI and biomarkers or subtypes of breast cancer.

Methods: A total of 280 women (mean age, 51 years; range, 28-79 years) with 282 invasive breast cancers (<5 cm) were included. The associations between the tumor roundness (1-100%), as measured using MRI software, and immunohistochemical (e.g. estrogen receptor [ER], progesterone receptor [PR], human epidermal growth factor receptor 2 [HER2], and Ki67) features were evaluated using Pearson's or Spearman's rank correlation coefficients and multiple linear regression analysis.

Results: An inverse correlation was observed between the ER (r = -0.408, P < 0.001) or PR (r = -0.248, P < 0.001) scores and tumor roundness, whereas a positive correlation was observed between the Ki67 index and tumor roundness (r = 0.354, P < 0.001). In multiple linear regression, the ER score (P < 0.001) and Ki67 index (P = 0.003) were independent factors determining tumor roundness. Triple-negative tumors (ER, PR, and HER2 negative) showed the highest mean roundness scores compared with the other subtypes (e.g. 67.3% for triple-negative, relative to 55.9% for HER2-enriched, 53.8% for luminal B, and 51.7% for luminal A, P < 0.001).

Conclusions: Our results suggest that breast tumors with lower ER expression and higher cellular proliferation or biologically aggressive triple-negative tumors are likely to manifest with relatively benign morphologic features.