Depending on the assay used, the results of several studies showed that ctDNA was able to identify relevant mutations or fusions including RAS, HER2/Neu, BRAF, MET, BRCA2, APC, TP53, ALK, ROS1, PTEN, and NF1. The prognosis in terms of tumor mutation burden, objective response rate, metastasis and survival were also estimated by various studies based on ctDNA. The gene discussed is ERBB2; the disease is neoplasm.