OBJECTIVETo investigate the effects of the volume of 4% neutral phosphate buffered formalin fixative solution on the detection of human epidermal growth factor receptor 2 () gene by fluorescencehybridization (FISH) in primary invasive breast cancer.

METHODSTissue 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 ofgene was detected by FISH. The gene amplification results ofwere observed and compared in different groups.

RESULTSFluorescence 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 ofwas gradually increased from group A to D(=8.601,<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<0.05).

CONCLUSIONSWhen using FISH to detectgene 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.