Effect of Fixation Period on HER2/neu Gene Amplification Detected by Fluorescence In Situ Hybridization in Invasive Breast Carcinoma

This study investigated if formalin fixation duration affects HER2/neu gene amplification detection by fluorescence in situ hybridization (FISH) in breast cancer. Tumor tissues from 35 cases were divided into three groups and subjected to two formalin fixation protocols per group (12 hr, 27 hr in the first; 2 hr, 17.5 hr in the second; 28.5 hr, 541 hr in the third) before FISH analysis. There was no significant difference in FISH signal detection between the two different fixation protocols in the first two groups. In the third, no signal was detected in 4/6 cases fixed for an extended duration.