Immunohistochemical Subtypes of Breast Cancer: Correlation with Clinicopathological and Radiological Factors.

BACKGROUND: The relationship between biomarkers and imaging features is important because imaging findings can predict molecular features.

OBJECTIVES: To investigate the relationship between clinicopathologic and radiologic factors and the immunohistochemical (IHC) profiles associated with breast cancer.

PATIENTS AND METHODS: From December 2004 to September 2013, 200 patients (mean age, 56 years; range, 29 - 82 years) were diagnosed with breast cancer and underwent surgery at our institution. Their medical records were reviewed to determine age, symptom presence, mammographic findings (including mass, asymmetry, microcalcifications, or negativity), sonographic Breast Imaging-Reporting and Data System (BI-RADS) category, pathologic type of cancer (invasive ductal, mucinous, medullary, or papillary carcinoma), histologic grade, T-stage, and IHC subtypes. Based on the IHC profiles, tumor subtypes were classified as luminal A, luminal B, human epidermal growth factor receptor 2 (HER2) enriched, or triple-negative (TN) cancers. Using univariate and multivariate logistic regression analyses, we looked for correlations between four IHC subtypes and two IHC subtypes (TN and non-triple negative [non-TN]) and clinicopathologic and radiologic factors, respectively.

RESULTS: Based on our univariate analyses with the four subtypes, the TN subtype showed a higher incidence of masses on mammography compared to the other subtypes (P = 0.037), and the TN subtype also tended to have the highest histologic grade among the subtypes (P < 0.001). With regard to the two IHC subtypes, the TN subtype had a significant association with medullary cancer (P = 0.021), higher histologic grade (grade 3; P < 0.001), and higher T stage (T2; P = 0.027) compared to the non-TN subtypes. In a multivariate logistic regression analysis of the clinicoradiologic factors compared to luminal A, the HER2 subtype had a significant association with BI-RADS category 4b (odds ratio [OR], 9.005; 95% confidence interval [CI], 1.414 - 57.348; P = 0.020) and borderline significance with category 4c (OR, 4.669; 95% CI, 0.970 - 22.468; P = 0.055). In a multivariate logistic regression analysis of the clinicoradiologic factors associated with the non-TN subtypes, the TN subtype was significantly correlated with medullary carcinoma (OR, 7.092; 95% CI, 1.149 - 43.772; P = 0.035).

CONCLUSION: These results suggest that patients with the TN subtypes are more likely to have higher-histologic-grade tumors and medullary cancer. The HER2 subtype was typically associated with a higher BI-RADS category.