Intratumoral Heterogeneity in Breast Cancer: A Comparison of Primary and Metastatic Breast Cancers

Intratumoral heterogeneity presents challenges in the management of cancer. To gain deeper insight in intratumoral heterogeneity at different levels and tumor sites for common biomarkers in breast cancers, this report examines seven cases of invasive breast cancer with multiple axillary nodal metastases and/or recurrences for immunohistochemical expression of estrogen receptors, progesterone receptors, human epidermal growth receptor 2, and Ki67 on all tissue blocks in both primary and metastatic tumors. This challenge of intratumoral heterogeneity in cancer management is the focus of this article. Seven cases of invasive breast cancer with multiple axillary nodal metastases and/or recurrences for immunohistochemistry expression of the important biomarkers for breast cancer treatment decisions (estrogen receptors, progesterone receptors, HER2, and Ki67) are presented.