Discordant HER2 status between primary breast carcinoma and recurrent/metastatic tumors using fluorescence in situ hybridization on cytological samples.

OBJECTIVE: The aim of this study was to show the usefulness of examining HER2 status on fluorescence in situ hybridization using cytological samples taken from recurrent/metastatic tumors.
METHODS: One hundred freshly aspirated or scraped cytological samples were obtained from locoregional recurrences or distant metastases. Fluorescence in situ hybridization assay for HER2 amplification was performed on both these samples and the formalin-fixed, paraffin-embedded tissues of the paired primary tumors of breast cancer, and the relationships between various clinico-pathological factors and HER2 amplification of both tumors were examined.
RESULTS: A change in HER2 status was observed in nine cases (9%): six cases (6%) underwent a positive-to-negative conversion in HER2 status and three cases (3%) underwent a negative-to-positive conversion in HER2 status. A positive-to-negative conversion of HER2 status was noted in 4 (36%) of 11 'luminal-B' cases. The change in HER2 status in recurrent or metastatic tumor was noted in more cases treated with drug therapy than in those with no drug therapy (P < 0.05; Fisher's exact probability). Although the time to relapse was 3 years or more in three cases showing a negative-to-positive conversion in HER2 status, the time to relapse was less than 3 years in six cases showing a positive-to-negative conversion (P < 0.05; Fisher's exact probability).
CONCLUSIONS: HER2 examination on fluorescence in situ hybridization using fine-needle aspiration cytology samples of tumors in recurrent/metastatic sites or disseminated tumor cells in effusion is beneficial, particularly when the primary tumor is not suitable for the testing of HER2 status or negative for HER2 amplification, because aspiration using a needle is technically feasible and not as traumatic as biopsy.