Recently published clinical trial data have produced compelling evidence for increased survival when Herceptin is administered to patients whose tumors are HER2 amplified. Therefore, the accuracy of HER2 status is essential to determine which patients should or should not receive Herceptin. Although HER2 results obtained by FISH and IHC are often in agreement, there is a persistent group of cases in which results are discordant, particularly among tumors with intermediate results. A multivariable analysis was undertaken to determine relative significance of various clinical and pathologic findings for patients diagnosed with infiltrating ductal carcinoma, and a data model was produced that predicts which patients are most likely to have HER2 amplified tumors. Correlates of HER2 amplification were higher Scarff-Bloom-Richardson grade, younger age at diagnosis, and a comedo ductal carcinoma in situ component.