Value of antimesothelioma HBME-1 in the diagnosis of inflammatory and malignant pleural effusions.

Pleural effusions occur in many benign and malignant conditions. The differentiation of mesothelial hyperplasia, malignant epithelial mesothelioma and metastatic adenocarcinoma in cytologic specimens is often difficult. Because many immunohistochemical studies had suggested that HBME-1 has a high sensibility but a low specificity for mesothelial differentiation, the authors investigate its utility in cytological specimens. In this study, immunostaining was performed on 30 smears from seven patients with inflammatory pleural effusions, 21 patients with metastatic pleural effusions and two patients with malignant epithelial mesothelioma. The immunoreactivity was evaluated by two independent observers. Benign mesothelial cells expressed HBME-1 in 13 (46.43%) cases with thick and thin membrane pattern and with thin membrane and cytoplasmic pattern in 11 (39.29%) cases. One of the malignant mesothelioma was positive for HBME-1 with thick and thin membrane pattern. Metastatic tumor cells were positive for HBME-1 in seven (33.33%) cases; the staining pattern in metastatic adenocarcinoma cells was thin membrane and focal cytoplasmic. HBME-1 has a moderate sensibility and specificity for mesothelial cells and can be used as part of a panel for differentiation of malignant and reactive mesothelial cells from adenocarcinoma in pleural effusions.