ERBB2 and breast carcinoma: Generally, our data corroborated that circ-ERBB2 might act as an oncogene in HER2-positive breast cancer development and provide two novel regulatory axes for HER2-positive breast cancer: circ-ERBB2/miR-136-5p/TFAP2C and circ-ERBB2/miR-198/TFAP2C.