Volume of 4% neutral buffered formaldehyde affects the results of HER2 gene detected by fluorescence in situ hybridization in primary invasive breast cancer

Abstract

To investigate the effects of the volume of 4% neutral phosphate buffered formalin fixative solution on the detection of human epidermal growth factor receptor 2 (HER2) gene by fluorescence in situ hybridization (FISH) in primary invasive breast cancer. Tissue samples were collected from 109 patients with primary invasive breast cancer admitted in Zhongshan Boai Hospital from June 2014 to October 2016. The ratios of 4% phosphate buffered formalin fixative solution to sample volume samples were 3:1, 6:1, 9:1, 10:1, 15:1, 20:1 or 25:1 (groups A, B, C, D, E, F and G), respectively. Paraffin sections were made after 15 h of fixation. The amplification of HER2 gene was detected by FISH. The gene amplification results of HER2 were observed and compared in different groups. Fluorescence microscope showed that the tissue contour in groups A, B and C was vague, cell debris appeared, and the probe was positioned poorly; while the tissue contour was clear and complete in groups D, E, F and G and the probe was positioned accurately. The positive rate of HER2 was gradually increased from group A to D(χ2=8.601, P<0.01), and that remained stable at 24.77% in groups D to G. The positive rate of gene amplification in groups D, E, F and G was significantly higher than that in groups A, B and C (all P<0.05). When using FISH to detect HER2 gene in samples of primary breast invasive carcinoma, the volume of fixative solution should be at least 10 times of the sample volume to obtain accurate and stable results.