Estrogen, progesterone, and insulin-like growth factor-1 (IGF-1), with their proliferative effects, are thought to be key hormones in breast cancer etiology.13–15 As proliferative effects of these hormones are largely mediated through their respective receptors,16,17 expression of these receptors in breast tissue may indicate tissue-specific responsiveness to these hormones. Here, IGF1 is linked to breast cancer.