One to four brown dots per nucleus were visualized under bright-field microscope in hematoxylin-counterstained sections in more than 80% of the nuclei in tissue samples from normal mammary gland, benign proliferative lesions, all 18 carcinomas without protein overexpression as well as 10 carcinomas with HER-2 protein overexpression. The gene discussed is ERBB2; the disease is carcinoma.