ERBB2 and neoplasm: Moreover, expression of t-erbB2s has been associated with lymph node and brain metastases.12,15,16 While patients with t-erbB2s may have worse progression-free survival under anti-HER2 trastuzumab therapy, these patients can benefit from other treatments, such as erbB2-selective tyrosine kinase inhibitors.17,18 Consequently, precise tumor classifications that include information about expression of truncated oncoprotein isoforms and CTFs— rare tumor markers—hold promise in guiding treatment decisions for specific patients.19