Ultrastructural studies of cells in body cavity effusions

Transmission electron microscopic examination of benign (16 cases) and malignant (2 cases) mesothelial cells and metastatic carcinoma (10 cases) was performed. These studies showed long, slender, branching and bushy microvilli with high length-to-diameter ratios to be the most important distinguishing features of the mesothelial cells. Cytoplasmic intermediate filaments were present in all mesothelial cells as well as in carcinoma cells. The mesothelial cells showed an absence of mucin vacuoles, intracellular lumens and luminal tight junctions, which are seen in adenocarcinoma cells. The pinocytotic vesicles were found to be more numerous in the mesothelial cells. Lipid vacuoles, lysosomes, Golgi apparatus and intercellular lumens appeared to be variably present in all mesothelial and carcinoma cells. The methodology is discussed and pertinent literature reviewed.