Clinicopathological analysis of lung cancer resembling malignant pleural mesothelioma

OBJECTIVE: The aim of this study was to evaluate the clinicopathological features of lung cancer resembling malignant pleural mesothelioma. METHODOLOGY: The seven patients studied had tumours showing an extensive pleural growth pattern, and were chosen from 1516 lung cancer patients diagnosed at two affiliated hospitals over a 17-year period. RESULTS: Histologically, five of these lung cancers were adenocarcinomas, one was a small cell carcinoma, and one a large cell carcinoma. Tumour markers such as carcinoembryonic antigen (CEA) were elevated in six patients at admission. However, a clinical diagnosis was difficult and these cancers could only be distinguished from malignant pleural mesothelioma by thoracentesis in two cases, pleural biopsy in two, thoracotomy in two, and in case 7 at autopsy. Treatment consisted of chemotherapy or radiation therapy in four patients, but with little clinical effect. The mean survival time was 6.7 months, which is much less than for true malignant pleural mesothelioma. CONCLUSIONS: Lung cancer resembling malignant pleural mesothelioma is most frequently observed in patients with adenocarcinoma, which is suspected to occur peripherally. To distinguish pseudomesotheliomatous carcinoma from malignant pleural mesothelioma in patients with diffuse pleural thickening and effusion, requires adequate tissue sampling by thoracotomy or video-assisted thoracoscopic surgery and a panel of immunohistochemical stains.