Cytologic diagnosis of malignant mesothelioma, with particular emphasis onthe epithelial noncohesive cell type

The effusion cytologies from 21 cases of malignant mesothelioma (MM) (15 pl eural, 6 peritoneal) diagnosed at the Indiana University Medical Center dur ing 1990-1997 were reviewed. Using the classification of Tao (Acta Cytol 19 79;23:209-213), 13 cases of MM were of the epithelial cohesive cell type an d 8 were of the epithelial noncohesive cell type. While the epithelial cohe sive cell type has been discussed in the literature, the epithelial noncohe sive cell type has nor. The cytomorphologic features for both types are pre sented with particular emphasis oil the noncohesive cell type. The differen tial diagnosis and use of ancillary confirmatory laboratory tests are brief ly discussed. Because of its resemblance to florid reactive mesothelial hyp erplasia and the general lack of awareness of the existence of the single-c ell pattern of mesothelioma, this diagnosis can often be missed. Diagn. Cyt opathol. 1999;20:57-62. (C) 1999 Wiley-Liss, Inc.