The objective of this project is to conceptualize an assay method to quantitate - oncogene products in cells and tissues. In the first Phase I efforts, the protein encoded by the HER2 oncogene, P185 HER2, will be used as a specific' example, since it has been strongly implicated in the biological behavior of breast cancer and may have prognostic significance. The techniques used will be those of high resolution digital image microscopy and immunohistochemical localization. Since immunohistochemistry permits analysis of individula cells, very small tissue samples can be used, enabling this assay to be performed on small lesions, biopsies or cytological smears of fine needle aspirates of breast tumors. However the disadvantage of immunohistochemical techniques is the manner. This research is aimed at improving this limitation. The proposed assay method, relying on digital image processing, will be a quantitative assay for oncogen expression in individual cells which can be performed easily and quickly on the malignant cells of a specimen sample.