ERBB2 and breast cancer: While, to date, TMEM doorway score has been associated with distant recurrence in only a subset of breast carcinomas (i.e., ER+HER2−) [5,7], TMEM doorways have been observed in preclinical models as well as clinical samples at the very early stages of breast cancer [29] as well as at metastatic sites such as the lung [30] and lymph nodes [31].