ERBB2 and neoplasm: Although not evaluated in this study, our ddPCR assay design with very short amplicons (≤59 bp) should be highly amenable to analysis of ERBB2 CN in other sample types including those where the DNA may be highly fragmented such as formalin-fixed paraffin embedded tissues (FFPE; <600 bp) as well as circulating tumor DNA (ctDNA; <200 bp) liquid biopsy samples.