The interclonal interactions leading to acquisition of metastatic capability could take place either in the primary tumor site prior to dissemination, where the non-tumorigenic clones are able to survive because they are supported by the microenvironment and are not challenged under anchorage-independent conditions in the ascites fluid, or within the peritoneum where small clusters of heterogeneous populations (ERBB2-amplified cells and AREG-high cells) are temporarily coexisting. This evidence concerns the gene ERBB2 and neoplasm.