Abstract
Objective and Study Design : We improved the cytopathological diagnosis of malignant mesothelioma (MM) in serous effusion by retrospectively evaluating the cytological features of 16 cases of histopathologically proven MM because only 7/16, or 43.8%, of cases were diagnosed as MM in the original diagnosis and compared cytopathological findings to those of reactive mesothelial cells (RM) in 65 cases benign serous effusion.
Results : An initial diagnosis of serous effusion from 16 cases of histologically proven cases of MM showed 7 cases of MM, 4 cases suspected of being MM, 4 cases of no malignancy, and 1 case of metastatic adenocarcinoma. Retrospective study revealed that 3 of 4 cases originally diagnosed as “no malignancy” had a few MM cells with individualized dispersed malignant cells, and smaller cell clusters than those detected in the cases initially diagnosed as MM. These malignant cells were nearly equal to or smaller than the average size of 65 RM (243.6μm2). The study of 4 of 5 cases originally diagnosed as “suspected MM” and as metastatic adenocarcinoma showed many MM cells, both single and in large cell aggregates. Cells and nuclei in these 4 cases were all significantly smaller than for RM.
Conclusions : MM showed a wide range of cytological features in serous effusion. The presence of small number and size of MM cells usually resulted in a cytological diagnosis of negative or suspected MM in our retrospective analysis. Complex arrangements of cells, thick cytoplasm, large eosinophilic nucleoli, and the number of multinucleated tumor cells should be used to differentiate RM from MM serous effusion, in addition to traditional diagnostic criteria.
