ERBB2 and neoplasm: Actionable molecular alterations have been found in approximately 30% of BTCs and include fibroblast growth factor receptor 2 (FGFR2) fusions, isocitrate dehydrogenase 1 (IDH1) sequence variations, v-raf murine sarcoma viral oncogene homologue B1 (BRAF) V600E sequence variations, and Erb-b2 receptor tyrosine kinase 2 (ERBB2; formerly HER2) amplifications.10,11 The frequency of these molecular alterations varies according to the anatomical location of the primary tumor.