The availability of silver stain to distinguish mesothelial cells from adenocarcinoma cells in ascites

We studied the ability of silver staining to distinguish reactive mesothelial cell clusters from adenocarcinoma cell clusters in ascites.We silver stained cytological smears of ascites from 24 patients with colon cancer, sixteen of which were class II and eight of which were class V.We observed 55 cell clusters which were cytologically diagnosed as mesothelial cells and 87 cell clusters which were cytologically diagnosed as adenocarcinoma cells. In 37 out of 55 (67.3%) cell clusters of mesothelial cells, clearly-defined silver-stained areas were observed in the center of the clusters.Although it was impossible to evaluate whether or not silver-stained areas existed in 32 out of 87 (36.8%) cell clusters of adenocarcinoma because of excessive staining, no silver-stained area was observed in the remainder (63.2%) of the adenocarcinoma cell clusters.In some adenocarcinoma cell clusters, linear silver-stained areas were observed along the peripheries of the clusters. We consider the silver-stained area to consist of fiberous connective tissue. In conclusion, silver staining can be used to differentiate between mesothelial cell clusters and adenocarcinoma cell clusters in ascites.