Importantly, our findings provide novel insight into the frequency of HER2 mRNA expression, which could be targetable with anti-HER2 therapies, as evidenced by our patient, who had advanced cholangiocarcinoma and high mRNA HER2 expression, but insufficient tissue for IHC or copy-number evaluation; this patient has responded to HER2-targeted therapy for ≥24 months. This evidence concerns the gene ERBB2 and cholangiocarcinoma.