ERBB2 and breast cancer: In breast cancer patients with no distant metastases receiving neoadjuvant chemotherapy, a positive correlation between PLK4 expression in cancerous tissues and occurrence of surrounding recurrence and distant metastases has been reported [109] In a stratified analysis, high expression of PLK4 mRNA has been reported to be associated with poor outcomes in patients with hormone receptor-positive, HER2-negative tumors [111].