Human malignant tumours of the breast, as compared to their respective normal tissue, have elevated expression of the Harvey ras oncogene.

Analysis of expression of Harvey-ras related oncogenes in human malignant breast tumours and in their respective normal tissue has revealed a significant elevation of Harvey-ras transcripts in malignant as compared to normal tissue. In contrast, the sis oncogene is not expressed significantly in either type of malignant or normal tissue. These results suggest that Harvey-ras oncogene may be specifically activated in the development of human malignant breast tumours.