In 1981, a novel transforming gene called neu, related to, but distinct from, the c-erbB protooncogene, was identified (1-3). In 1985, two groups independently isolated identical erbB-related genes from human DNA that they called HER-2 (4) and c-erbB-2 (5) located at chromosome band 17q11.2 and encoding a 185,000 Dalton tyrosine kinase (2,4). Studies conducted on human breast cancers showed 28% to have amplified HER2/neu present (7) and it was suggested that amplification or increased protein expression might confer a selective advantage (6). Over the last ten years, many studies have confirmed the value of using overexpression or amplification of the HER2/neu gene as a predictor of poor outcome in cases of breast cancer (7-9). Clinical trials are currently underway using anti-HER2/neu in an attempt to destroy malignant breast cells (10,11).