The histologic distinction between desmoplastic mesothelioma and reactive fibrosis and between biphasic desmoplastic mesothelioma and pleural metastases with desmoplasia can be difficult. The presence of such epithelial markers as keratin and epithelial membrane antigen (EMA) within the fibrous areas of a pleural lesion might be construed as evidence in support of the diagnosis of desmoplastic mesothelioma. To test this hypothesis ten desmoplastic mesotheliomas were studied with monoclonal antisera to keratin and EMA and compared with ten hyaline pleural plaques, 11 pleural scars, five benign localized fibrous mesotheliomas, and eight desmoplastic pleural metastases. Although the hyalinized fibrous areas within the desmoplastic mesotheliomas stained with keratin (ten of ten) and EMA (five of ten), the following reactive fibrous pleural lesions were also positive: plaques (four of ten keratin-positive, five of ten EMA-positive); scars (six of 11 keratin-positive, four of 11 EMA-positive); and fibrosis induced by metastases (six of eight keratin-positive, one of eight EMA-positive). Benign localized fibrous mesotheliomas were keratin-and EMA-negative. This study suggests that both benign and malignant fibrous pleural lesions may be of mesothelial origin and demonstrates the need to determine by histologic criteria whether the spindle cell component is benign or malignant before assessing the significance of its keratin or EMA immunoreactivity. The lack of keratin and EMA staining in benign localized fibrous mesotheliomas might be of use in distinguishing benign localized cellular fibrous mesotheliomas from sarcomatous mesotheliomas.
ASJC Scopus subject areas
- Pathology and Forensic Medicine