Background: Breast cancer subtypes (BCS) determined from immunohistochemical staining have been correlated with molecular subtypes and associated with prognosis and outcomes, but there are limited data correlating these BCS and axillary node involvement. This study was conducted to assess whether BCS predicted for nodal metastasis or was associated with other clinicopathologic features at presentation.
Methods: Patients with stage I/II disease who underwent breast-conserving surgery and axillary surgical assessment with available tissue blocks underwent a institutional pathological review and construction of a tissue microarray. The slides were stained for estrogen receptor, progesterone receptor, and HER-2/neu (HER-2) for classification into BCS. Nodal involvement and other clinicopathologic features were analyzed to assess associations between BCS and patient and tumor characteristics. Outcomes were calculated a function of BCS.
Results: The study cohort consisted of 453 patients (luminal A 48.6%, luminal B 16.1%, HER-2 11.0%, triple negative 24.2%), of which 22% (n=113) were node positive. There were no significant associations with BCS and pN stage, node positivity, or absolute number of nodes involved (p>0.05 for all). However, there were significant associations with subtype and age at presentation (p<0.001), method of detection (p=0.049), tumor histology (p<0.001), race (p=0.041), and tumor size (pT stage, p<0.001) by univariate and multivariate analysis. As expected, 10-year outcomes differed by BCS, with triple negative and HER-2 subtypes having the worse overall (p=0.03), disease-free (p=0.03), and distant metastasis-free survival (p<0.01).
Conclusions: There is a significant association between BCS and age, T stage, histology, method of detection, and race, but no associations to predict nodal involvement. If additionally validated, these findings suggest that BCS may not be a useful prognostic variable for influencing regional management considerations.