The value of occult disease in resection margin and lymph node after extrapleural pneumonectomy for malignant mesothelioma

BACKGROUND: The purpose of this study was to examine the prognostic impact of occult disease after extrapleural pneumonectomy for malignant mesothelioma. METHODS: We reviewed the resection margin and node specimens from 41 consecutive patients undergoing extrapleural pneumonectomy for malignant pleural mesothelioma in different institutions between 1985 and 2004. The specimens were reassessed by immunohistochemical staining with anticalretinin and antimesothelin monoclonal antibodies, and results were used to draw Kaplan-Meier survival curves and perform Cox regression analyses. RESULTS: Histologic examination showed 34 epithelioid, 4 biphasic, and 3 sarcomatoid subtypes. Results of postoperative TNM staging were that 14 patients were in stage I, 6 were in stage II, and 21 were in stage III. One patient died during the early postoperative period. Median survival was 13 months. Survival was affected by nonepithelial histologic type (p = 0.001), TNM stage (p = 0.007), positive resection margins (p = 0.002), and N disease (p = 0.01). Immunohistochemistry revealed occult positive resection margins in 6 patients, not correlated with T stage. Microscopic N disease was discovered in 5 patients, of whom 2 had their nodes retrieved through cervical mediastinoscopy. No correlation with nodal diameter was found. In all patients microscopic N disease could have been accessible through mediastinoscopy. Overall, the presence of occult disease was diagnosed in 5 new patients and influenced survival more than any other variable, both at univariate (p < 0.001) and multivariate Cox regression analysis (p < 0.0001; odds ratio, 5.4; 95% confidence interval, 3 to 15). CONCLUSIONS: In malignant pleural mesothelioma, the presence of occult disease in resection margins and lymph nodes can be identified by immunohistochemistry and significantly influences the prognosis. Cervical mediastinoscopy is useful in all patients considered for radical resection, but all specimens should be processed with immunohistochemical staining.