Publication Year: 2000 Visited: 65

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HER2 Expression in Breast Cancer: How Reliable is Immunohistochemical Determination in Core Biopsy? Elisabeth Mueller-Holzner, Vroni Fink, Thomas Frede, Christian Marth, Dept of Obstetrics and Gynecology, Innsbruck, Austria; Dept of Radiology II, Innsbruck, Austria.

HER2 overexpression occurs in about 25 - 30 % of breast cancers and is associated with a poor prognosis and a lack of response to hormone therapy. Trastuzumab (Herceptin), a humanized monoclonal antibody against HER2, shows therapeutic benefits in patients with HER2 overexpressing tumors. For preoperative therapy planning, core biopsy of tumors offers the opportunity to obtain the histological diagnosis and estimates of prognostic and predictive parameters via immunohistochemistry. In sixty-one patients with invasive breast cancer core biopsies and sections of the subsequently removed whole tumor specimen were investigated immunohistochemically for overexpression of HER2 with the DAKO HercepTest (DAKO, Glostrup, Denmark). Fifteen tumors (25 %) revealed HER2 overexpression and 42 tumors (69 %) were negative in both, the core biopsy and the final sections of the whole tumor. One core biopsy was negative whereas the corresponding final specimen showed HER2 overexpression. In 3 cases weak overexpression was observed in the core biopsy, but the whole tumor had to be estimated as negative according to the instructions for interpretation of staining. There was an overall concordance of the results achieved at core biopsy and whole tumor sections of 93% (kappa = 0,79). We thus conclude, that the immunohistochemical investigation of core biopsies offers the opportunity for a valid preoperative estimation of HER2 overexpression in breast carcinoma.