Notably, we report a case in which a patient with ERBB2-amplified PDAC (in the absence of co-occurring KRAS mutations) responded to anti-HER2 therapy for several months with clinical improvement and decline of tumor markers, before demonstrating a KRAS alteration newly detected by cfDNA and loss of ERBB2 amplification via cfDNA after progression. This evidence concerns the gene ERBB2 and neoplasm.