Parathyroid hormone-related protein antigen localization distinguishes between mesothelioma and adenocarcinoma of the lung

The distinction between pleural malignant mesothelioma and pulmonary adenocarcinoma remains a problem in diagnostic histopathology. Parathyroid hormone-related protein (PTHrP) has been demonstrated in the neoplastic cells of malignant mesotheliomata, using a polyclonal antiserum raised to synthetic PTHrP(1–16). In a series of 44 malignant mesotheliomata and 44 cases of pleural adenocarcinomata, PTHrP was localized immunohistochemically in 84 per cent of the mesotheliomata and in 11 per cent of the pleural adenocarcinomata. Normal and reactive mesothelium did not contain detectable PTHrP. The presence of PTHrP in a very high percentage of malignant mesotheliomata indicates the value of including it in the panel of antibodies utilized in the differential diagnosis of mesothelioma.