Keratins of different molecular weight in exfoliated mesothelial and adenocarcinoma cells--an aid to cell identification.

Keratin profiles of exfoliated mesothelial and adenocarcinoma cells were determined using antisera to different molecular weight keratins (45, 46, 55, 63 kdaltons) and the immunoperoxidase technic. Most metastatic adenocarcinomas in effusions stained for low (45, 46 kdaltons) and intermediate (55 kdaltons) molecular weight keratins but were negative for 63 kdalton keratin. In contrast, most reactive and malignant mesothelial cells in effusions stained strongly for 63 kdalton keratin and keratins of lower molecular weight. This is the first report of high molecular weight (greater than 60 kdaltons) keratin in exfoliated cells of nonepidermal origin. Differences in staining for 63 kdalton keratin between mesothelial and adenocarcinoma cells may help to distinguish these cells in effusions.