Abstract: Background and purpose: Adequate tissue fixation, transparent dewaxing is an important step of hematoxylin eosin (HE) staining and fluorescence in situ hybridization (FISH) in detection of breast cancer HER-2 gene. The purpose of this study was to make a comparison between poly hydroxyl acrylic acid which is an environmentally friendly fixation liquid and 4% neutral buffered formaldehyde in tissue fixation for HE staining and FISH to detect the HER-2 gene in the breast cancer tissue sections. The study aimed to evaluate the feasibility of replacing 4% buffered formaldehyde, a traditional fixation liquid, with the poly hydroxyl acrylic acid, an environmentally friendly fixation fluid. Methods: This project was performed on tissue samples collected from 69 cases of breast cancer, 41 cases of breast fibroadenoma, 40 cases of uterine leiomyoma, 25 cases of cervical tissue, 25 cases of placenta obtained from the outpatient and inpatient departments of Zhongshan Boai Hospital from Mar. 2011 to Jan. 2015, from each of which two samples were drawn and two blocks of each specimen were divided into two groups randomly. Then one group was fixed with 4% neutral buffered formaldehyde and made into 200 sections by HE while the other group was fixed with poly hydroxyl acrylic acid and made into another 200 sections. The slice level of the two groups was determined by the staining condition of the sections, and SPSS 19.0 was employed to compare the excellent and good rate of HE staining. Additional 69 sections were produced with two groups of breast invasive ductal carcinoma tissues, and SPSS 19.0 was used to detect the amplification of HER-2 gene by FISH. Results: First, the number of best-quality slices stained with HE fixed separately by poly hydroxyl acrylic acid and 4% neutral buffered formaldehyde was 155 and 166, respectively. The number of excellent pieces was 41 and 33, respectively, while the number of mediocre pieces was 3 and 1 with bad pieces being 1 and 0, respectively. The excellent and good rates of HE staining were 98% and 99.5%, respectively. There was no significant difference between the two groups (χ²=1.33, P>0.05).Second, the positive rates of the tissue slices by FISH fixed separately by poly hydroxyl acrylic acid and 4% neutral buffered were 26.09% and 23.19%, respectively. There was no significant difference between the two groups (χ²=0.50, P>0.05).Conclusion: The results obtained with HE staining and FISH using poly hydroxyl acrylic acid as a fixation liquid are not significantly different from those using 10% neutral buffered formaldehyde. Therefore, poly hydroxyl acrylic acid meets the requirements of environmental protection, and thus has the potential to be promoted and widely used.

Key words: Poly hydroxyl acrylic acid, Formaldehyde, Tissue section, Hematoxylin eosin staining, Breast cancer, HER-2 gene, Fluorescence in situ hybridization