We examined the usefulness of ultra-rapid immunostaining of ascitic fluid for HNF4α, which is expressed in abundance in the gastrointestinal tract epithelium, for rapid and precise intraoperative cytological diagnosis of gastric cancer. In this examination, we used the R-IHC® system to obtain rapid results, and the results revealed that HNF4α was specifically expressed in gastric cancer cells and that no positively stained cells were found in other malignancies such as lung cancer, or in benign conditions. Therefore, ultra-rapid HNF4α immunostaining of ascitic fluid using R-IHC® was useful for rapid intraoperative cytological diagnosis of gastric cancer.
