CYP19A1 and breast cancer: In our study, we have developed nanoemulsion‐based transdermal creams containing third‐generation aromatase inhibitors Exemestane (EXE) or Letrozole (LE) and evaluated their toxicity, anti‐tumour effects and androgenic potency using preclinical models including Bama minipigs, DMBA‐induced breast cancer rats and orchidectomized male rats.