INTRODUCTION: HER-2/neu overexpression has been tested using immunohistochemistry as a reliable and cost-effective method to select patients with invasive mammary carcinomas (IMC) for trastuzumab treatment, but there is no consensus regarding the best antibody to be used. The aim of the present study was to test five different antibodies for determining the status of HER-2/neu overexpression in IMC. MATERIAL AND METHODS: Sixty-six formalin-fixed, paraffin-embedded IMC were investigated by immunohistochemistry, using two polyclonal antibodies, HercepTestTM (Dako) and A0485 (Dako), and three monoclonal antibodies, the clone CB11, from both Novocastra Laboratories and from Biogenex, and the clone 4D5 (Genentech). All immunostainings were scored according to the guidelines for the HercepTestTM. RESULTS: The A0485 was positive in 25 cases (37.9%). The HercepTestTM was positive in 14/66 cases (21.2%). Both CB11 antibodies yielded a positive reaction in the same nine patients (13.6%). The 4D5 was positive in only 4/66 cases (6.1%). All positive cases for CB11 or 4D5 were HercepTestTMpositive. All cases positive for HercepTestTM were positive for A0485. Most of the HercepTestTM and A0485 2+ cases were negative when using the other antibodies. DISCUSSION: There was a higher number of cases presenting HER-2/neu positivity with the A0485 and HercepTestTM than with the other antibodies, primarily in cases scored as 2+. There was no difference in positivity when the CB11Ab was used, regardless of company. CONCLUSION: The use of immunohistochemistry for the clinical assessment of HER-2/neu overexpression still needs prospective validation.
Breast cancer; HER-2/neu; c-erbB-2; Immunohistochemistry; Pathology
