UTILITY OF CYTOKERATIN 20 IN IDENTIFYING THE ORIGIN OF METASTATIC CARCINOMAS IN EFFUSIONS

Using a commercially available monoclonal antibody (K(s)20.1) and the avidin-biotin peroxidase method on cytospins and cell blocks, we analy zed cytokeratin (CK) 20 expression in 169 serous effusions. Cytoplasmi c staining was observed in 44/151 malignant fluids. Colon, gastric, an d pancreatic adenocarcinomas and mucinous ovarian tumors were most fre quently positive. Single cases of transitional-cell and squamous cell carcinomas were reactive as well. Lung and breast cancers were mostly negative. Nonmucinous ovarian tumors were invariably unlabeled as were mesotheliomas and normal mesothelial cells. The study shows that CK 2 0 is valuable in distinguishing tumor cell origin in effusions. In par ticular, it identifies a set of carcinomas with the majority arising f rom the gastrointestinal tract, and represents a highly characteristic s marker for colorectal cancer. Diagn Cytopathol 1995; 12:303-308. (C) 1995 Wiley-Liss, Inc.