Interestingly, either correlations of PTK7 expression with clinicopathological parameters by tissue microarray IHC staining or online RFS analysis by Kaplan-Meier Plotter (http://www.kmplot.com/) demonstrated that PTK7 expression extraordinarily correlates with worse prognosis in ER/PR/HER2-negative (TNBC) breast cancer, which suggested a special relationship of PTK7 expression with worse prognosis in TNBC. Here, ESR1 is linked to breast cancer.