Variation in hormone receptor and HER-2 status between primary and metastatic breast cancer: review of the literature.

Importance of the field: Hormone and human epidermal growth factor receptor 2 (HER-2) receptors are two important pharmaceutical targets that affect the survival of patients with metastatic breast cancer. Discordance of hormone and HER-2 receptors were reported in a series of studies. Receptor status was reported to change in both directions, yet alteration occurs mostly in the loss of positivity for both receptors. We do not know both the exact mechanism of this process or the contribution rate of technical mistakes; a number of mechanisms might be responsible. Factors suggested include: tumor heterogeneity, clonal selection of tumor cell subpopulations, genetic instability of tumor cells, local or systemic treatments, the time interval between primary tumor and metastasis, receptor status determination techniques, and the site of metastasis. Areas covered in this review: Studies of estrogen, progesterone and HER-2 receptor discordance between primary and metastasis of breast cancer are summarized. Labor...