Estudo imunoistoquímico comparativo entre seis anticorpos anti-her2 emarrays de carcinomas mamários: correlação com hibridação in situ cromogênica e avaliação interobservador

Abstract

AIMS: We compared the novel rabbit monoclonal antibody SP3 with mouse monoclonal and rabbit polyclonal antibodies using tissue microarrays (TMA) of breast carcinomas correlating the results with chromogenic in situ hybridization (CISH). MATERIALS AND METHODS:Serial sections from TMAs containing 84 breast carcinomas were submitted to CISH (Zymed HER2 Spot-LightÒ kit) and immunohistochemistry, using SP3 (NeoMarkers), rabbit polyclonal antibodies A0485 and HercepTest (Dako), mouse monoclonal antibodies CB11 (Novocastra and CellMarque), and 4D5 (Genentech). All tests were performed in duplicate and sections were double-blindly evaluated using the HercepTest scoring system and Zymed HER2 interpretation guide for CISH. For the interobserver agreement evaluation, one slide from each antibody was independently scored by five observers and results evaluated considering three analysis: I (0; 1+; 2+; 3+); II (0 and 1+; 2+ and 3+) and III (0 and 1+; 2+; 3+). Kappa statistics was applied for data analysis. RESULTS: From antibodies comparison,the best concordance was observed between SP3 and HercepTest (kappa=0.74). SP3, A0485, and HercepTest detected all HER2 amplified cases. There were 5 non-amplified cases (13%) scored as 3+ using SP3, 2 cases (5.3%) using HercepTest, and 10 (26.3%) cases using A0485. Three amplified cases (6.5%) were negative for CB11 and 1 case (2.2%) was negative for 4D5. There was a good rate of interobserver agreement when four scores were considered (0; 1+; 2+; 3+). When the scores were considered in two categories (0 and 1+; 2+ and 3+), a substantial rate of interobserver agreement was considered for casesstained for SP3 and CB11, and almost perfect for cases stained for A0485, HercepTest and 4D5. For analysis III (0 and 1+; 2+; 3+), a moderate rate of interobserver agreement was considered for cases stained for CB11, and a substantial rate for other antibodies.CONCLUSIONS: The novel SP3 is more sensitive than monoclonal antibodies CB11 and 4D5 for Her2 assessment. However, HercepTest, CB11 and 4D5 show higher specificity than SP3. The overall interobserver agreement was considered moderate to substantial in theevaluation of cases stained for the five antibodies. The lowest rate of agreement was obtained in the evaluation of cases scored as weak (1+) and moderate (2+).