BACKGROUND: Evaluation of HER-2 status is essential for selecting appropriate candidates for treatment with trastuzumab, a recombinant humanized monoclonal antibody active against human epidermal growth factor receptor-2 (HER-2) protein. METHODS: To standardize a HER-2 diagnostic system for breast cancer tissue, we compared immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH) results. We studied specimens from 110 patients with invasive ductal breast cancer who underwent operation. IHC analysis was performed using HercepTestTM (Dako A/S), and results assessed according to the HercepTestTM criteria. FISH was performed using a PathVysionTM HER-2 DNA probe kit (Vysis Inc.), with specimens considered HER-2 positive if the ratio of the total HER-2 signals to chromosome 17 centromere (CEP17) signals was greater than 2. RESULTS: FISH results were indefinite in 3 patients and positive in 24 patients (22%). IHC scores were 0 in 27 patients (25%), 1+ in 53 patients (48%), 2+ in 10 patients (9%), and 3+ in 20 patients (18%). All 20 patients with a score of 3+ by IHC were positive by FISH, with only 1 (10%) of 10 patients with an IHC score of 2+ positive by FISH. CONCLUSIONS: Our results indicated that an IHC score of 3+ is equivalent to FISH-positivity for HER-2 diagnosis, while patients with an IHC score of 2+ should undergo FISH testing.
BACKGROUND: Evaluation of HER-2 status is essential for selecting appropriate candidates for treatment with trastuzumab, a recombinant humanized monoclonal antibody active against humanepidermal growth factor receptor-2 (HER-2) protein. METHODS: To standardize a HER-2 diagnostic system for breast cancer tissue, we compared immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH) results. We studied specimens from 110 patients with invasive ductal breast cancer who underwent operation. IHC analysis was performed using HercepTestTM (Dako A/S), and results assessed according to the HercepTestTM criteria. FISH was performed using a PathVysionTM HER-2 DNA probe kit (Vysis Inc.), with specimens considered HER-2 positive if the ratio of the total HER-2 signals to chromosome 17 centromere (CEP17) signals was greater than 2. RESULTS: FISH results were indefinite in 3 patients and positive in 24 patients (22%). IHC scores were 0 in 27 patients (25%), 1+ in 53 patients (48%), 2+ in 10 patients (9%), and 3+ in 20 patients (18%). All 20 patients with a score of 3+ by IHC were positive by FISH, with only 1 (10%) of 10 patients with an IHC score of 2+ positive by FISH. CONCLUSIONS: Our results indicated that an IHC score of 3+ is equivalent to FISH-positivity for HER-2 diagnosis, while patients with an IHC score of 2+ should undergo FISH testing.