Abstract
The Ki67 proliferation rate of mesothelial cells was determined in 20 effusions due to malignant mesotheliomas and in 20 non-neoplastic effusions, to investigate if this marker may be useful to identify neoplastic mesothelioma cells and if there is a correlation between proliferation rate and survival time. Using the ABC-method, effusions were immunostained and the marker Ki67 was evaluated quantitatively. Ki67 proliferation fraction showed rates from 2.3% to 70% in malignant mesothelioma cells and from 1.8% to 25.5% in reactive mesothelial cells. A significant difference was found (p=0.05) between those two groups. Assuming a threshold at 26%, a sensitivity of 25% and specificity of 100% resulted. Yet, due to its low sensitivity this marker seems not to be useful for differential diagnosis. Plotting surviving period against Ki67 proliferation fraction a correlation was observed which was not significant. Long term survivors (>28 month) showed proliferation rates below 3.8%. Unexpectedly a highly significant difference (p=0.001) between Ki67 proliferation rates of mesothelial cells from patients with malignant tumors other than mesothelial origin (7.0% to 25.5%) and mesothelial cells of patients without any malignant disease (1.8% to 16.3%) were observed. Setting a threshold at 10% for identification of a malignant disease, a sensitivity of 77.8% and specificity of 90.9% resulted.