Fluorescence in situ hybridization for detecting erbB-2 amplification in breast tumor fine needle aspiration biopsies.

To evaluate the feasibility of erbB-2 amplification analysis of fine needle aspiration (FNA) biopsies.FNA smears and dissociated nuclei from 58 breast cancer samples were examined by dual-labeling fluorescence in situ hybridization (FISH) with probes for centromere 17 and the erbB-2 gene. The results were compared with the outcome of erbB-2 immunohistochemistry.Tumors were categorized according to the erbB-2/centromere 17 signal ratio. There were 23 tumors with high-level amplification, four cases with a low-level erbB-2 gain and 27 tumors with normal erbB-2 content. Four tumors showed an erbB-2 deletion, all in patients < or = 42 years of age. ErbB-2 amplification was strongly associated with positive erbB-2 immunostaining (P < .0001). Comparison of FISH analysis on dissociated cells and on FNA biopsies showed high correspondence (P < .0001).FISH allows reliable detection of erbB-2 gene amplification on FNA biopsies.