Basal-like immunophenotype markers and prognosis in early breast cancer.

AIMS AND BACKGROUND Basal-like breast cancer is a distinct group of tumors with heterogeneous behavior, and not all have a poor prognosis. The present study analyzed the prevalence and prognosis of early basal-like breast cancer. METHODS AND STUDY DESIGN A total of 112 patients with stage I and II breast cancer were retrospectively analyzed using immunohistochemical stains for estrogen receptor, progesterone receptor, HER2, cytokeratin 5/6 and epidermal growth factor receptor. Basal-like tumors were defined as being estrogen receptor, progesterone receptor and HER2 negative and cytokeratin 5/6 and/or epidermal growth factor receptor positive. RESULTS Of the 112 cases, respectively 13 (11.6%) were basal-like, 77 (68.8%) luminal A or B, 13 (11.6%) HER2 positive and 9 (8%) undefined. In basal-like tumors, epidermal growth factor receptor and cytokeratin 5/6 expression was positive in 5 patients (38.5%) and 12 patients (92%), respectively. There was no significant correlation between basal-like breast cancer and age (P = 0.207), lymph node status (P = 1.0) or clinical stage (P = 0.53). Among all tested biomarkers, positivity was found in 81 (72.3%) for estrogen receptor, 13 (11.6%) for HER2, 11 (9.8%) for epidermal growth factor receptor and 36 (32.1%) for cytokeratin 5/6. Epidermal growth factor receptor expression was significantly correlated with estrogen receptor-negative (P = 0.01) and HER2-positive (P = 0.02) tumors. During a median follow-up of 81 months, there were 26 (23%) disease relapses and 12 (10.7%) deaths. No significant difference relating to disease-free survival and overall survival was noted between basal-like breast cancer and subtypes luminal A and B, HER2 positive and undefined. CONCLUSIONS The addition of cytokeratin 5/6 and epidermal growth factor receptor defines a small subgroup of patients with basal-like tumors. In a population with early breast cancer, basal-like tumors did not have a prognosis different from the other subtypes. Neither was there a significant association with clinicopathological features. The high frequency of epidermal growth factor receptor positivity in estrogen receptor-negative and HER2-positive tumors represents a potential target in clinical trials.