Her-2 status evaluation in breast cancer has prognostic and treatment response value but its interobserver variation among pathologists is a problem since it is not quantitatively assayed. This study presents an immunohistochemiluminescence method to quantify Her-2 in breast cancer. Anti-Her-2 antibody was conjugated to acridinium ester (AE) and used to evaluate/quantify Her-2 status in breast Invasive Ductal Carcinoma (IDC, n=50) comparing with traditional immunohistochemistry. Anti-HER-2-AE results were expressed in Relative Lights Units (RLU) and showed to be able to distinguish and quantify the differences between the three groups of Her-2 status. 3+ Her-2 status presented the highest RLU (246,982 × 10(3) ± 2.061 × 10(3)) compared to 2+ (76,146 × 10(3) ± 0.290 × 10(3)), negative (27,415 × 10(3) ± 1.445 × 10(3)) and normal tissues (27,064 × 10(3) ± 2.060). Status differences were significant between 3+ and 2+ (p=0.0025); 2+ and negative (p=0.0003), and +3 and +1 (p=0.0001) beside this, normal breast control RLU was 27,064 × 10(3) ± 2,060 × 10(3), similar to negative cases. Results showed that anti-HER-2-AE conjugate was effective in breast tumors Her-2 status evaluation, allowing its quantitative establishment to consequently decrease the subjectivity in prognostic and predictive information intrinsic to this test.