Abstract
Mesothelioma is one of diseases that is showing an increase in incidence in recent years. The cytologic characteristics of mesothelioma are widely variable. To distinguish mesothelioma from adenocarcinoma or reactive mesothelial cells is difficult, and consequently the diagnostic accuracy by cytology is not high. Here, we analyzed the appearance ratio of intracytoplasmic vacuole cells as it seems to be a useful means to distinguish mesothelioma from reactive mesothelial cells. Body cavity effusions in 17 cases of epithelial mesothelioma and 10 cases of reactive mesothelial cells were analyzed. Intracytoplasmic vacuole cells were classified as: 1) peripheral vacuole-like (PV) cells, 2) central vacuole (CV) cells, and 3) vacuole (V) cells that lack PV and CV cell features. Comparison of the appearance of intracytoplasmic vacuole cells between mesothelioma and reactive mesothelial cells revealed that the appearance ratio of PV cells was significantly high in mesothelioma. We further analyzed the structural features of mesothelioma. Mesothelioma was subclassified into two groups; group A shows a solid cluster and group B shows a flat cluster or isolated cells, namely a non-solid cluster. Comparison of the vacuole cells in groups A and B indicated that the appearance of PV and CV cells was significantly higher in group B. These findings suggested that the appearance ratio of PV and CV cells is useful to distinguish mesothelioma from reactive mesothelial cells, particularly in cases of mesothelioma that show a flat cluster or an isolated cell and mimic reactive mesothelial cells. Thus, when PV or CV cells are identified, intensive clinical examinations are necessary for the diagnosis of mesothelioma. The present findings provide a clue for the diagnosis of mesothelioma that may be misdiagnosed as reactive mesothelial cells in effusion cytology.
