ERBB2 and breast cancer: The heterogeneity of TZM intracellular distribution has been shown previously in HER2‐positive breast cancer and ovarian carcinoma cells.[4, 21, 23, 24] Herein, we performed a comparative analysis of the intracellular distribution of TZM and HER2 in different human breast (AU565 and XTM) and ovarian (SKOV‐3) HER2‐positive cell lines, which vary in their morphological and physiological nature as well as tumor aggressiveness.[4] XTM are AU565‐tumor passaged cells that maintain their HER2‐positive nature.