The role of desmin and N-cadherin in effusion cytology - A comparative study using established markers of mesothelial and epithelial cells

The objective of the present study was to analyze the role of the mesotheli al markers desmin and N-cadherin in the diagnostic panel of serous effusion s. A total of 181 pleural and peritoneal effusions consisted of 101 cases c ytologically diagnosed as malignant (89 carcinomas, 12 mesotheliomas), 78 b enign, and 2 inconclusive specimens. All specimens were immunostained using 11 antibodies, against epithelial membrane antigen, BerEP4, carcinoembryon ic antigen, E-cadherin, CA 125, N-cadherin, desmin, calretinin, p53, viment in, and CD45. After evaluation of immunocytochemistry results, 110 specimen s were diagnosed as malignant (98 carcinomas, 12 mesotheliomas) and 71 as b enign (56 cellular, 15 paucicellular). The presence of desmin was detected in benign mesothelial cells in 47 of 56 (84%) reactive cellular specimens c ompared with I of 12 (8%) malignant mesotheliomas and 2 of 98 (2%) carcinom as. N-cadherin was expressed in 48 of 56 (86%) reactive cases, 12 of 12 (10 0%) mesotheliomas, and 47 of 98 (48%) carcinomas, In carcinomas, N-cadherin expression was most often seen in ovarian carcinoma but was also found in other carcinomas. Calretinin, an established marker of mesothelial cells, w as detected in 52 of 56 (93%) reactive specimens, 11 of 12 (93%) mesothelio mas, and 3 of 98 (3%) carcinomas. Evaluation of staining results led to rec lassification of six malignant specimens as benign, whereas 17 cases diagno sed as benign and the two diagnosed as inconclusive were classified as mali gnant. In conclusion, desmin appears to be a promising marker for the disti nction between reactive mesothelium and malignant epithelial cells in terms of both specificity and sensitivity, and its complementary use with calret inin is recommended. Unlike calretinin, it may also prove valuable for the distinction between benign and malignant mesothelial cells. N-cadherin does not have a role in the distinction between mesothelial and epithelial cell s. However, it may prove useful in the characterization of carcinomas of un known origin. As has previously been shown, a significant number of diagnos es that are based on morphologic examination alone are modified after the u se of a broad antibody panel.