ERBB2 and metastatic neoplasm: In this multicenter study, women with HER2-negative metastatic disease and at least one HER2-positive CTC are enrolled in the DETECT III trial (NCT01619111), and women with HER2-negative BC (hormone receptor-positive or triple-negative) and exclusively HER2-negative CTCs are eligible for the DETECT IV trial (NCT02035813).