HER1- and HER2-overexpressing cancer cell lines, including A431 human epidermoid (3×106 HER1 receptors/cell [21]) and human ovarian carcinoma SKOV-3 (2.6×105 HER2/neu receptors/cell [22]) cells, were chosen to test specific staining of tumor cells with self-assembling fluorescent complexes. This evidence concerns the gene ERBB2 and cancer.