PTK7 and breast cancer: No significant association between PTK7 protein expression and breast cancer-specific survival of ER-negative (p = 0.582), ER-positive (p = 0.836), PgR-negative (p = 0.651), PgR-positive (p = 0.997), HER2-negative (p = 0.060), or HER2-positive patients (p = 0.854) was observed.