Prevalence and Pattern of Lymph Node Metastasis in Malignant Pleural Mesothelioma

Background The incidence and pattern of nodal metastases in mesothelioma are not well understood. This study was conducted to evaluate the prevalence and pattern of nodal metastasis in mesothelioma patients. Methods The study included 53 patients with mesothelioma. The first 37 patients (group I) underwent combined modality treatment without preoperative mediastinoscopy. The second group included 16 patients (group II) with pretreatment mediastinoscopy. Results A total of 18 patients had positive lymph nodes, 12 in group I and 6 in group II; of the latter, 4 had positive mediastinoscopy and 2 had positive nodes on final pathology. Postoperatively, a mean of 14 nodes were dissected (range, 5 to 34). In the post-pleuropneumonectomy group, 6 of 14 patients had positive hilar node metastases in addition to positive mediastinal lymph nodes. One patient had positive hilar nodes only. Of the 49 patients operated on, only 7 had no lung invasion by pathologic evaluation, and none had positive hilar nodes. The mechanism of spread of the disease to hilar nodes may be through lung invasion and not due to direct spread from the pleura. This observation raises the possibility that mediastinal nodes should be considered the primary station in patients with mesothelioma, whereas hilar node metastasis necessitated lung invasion first. Conclusions The pattern of nodal metastases may be different from that of lung cancer, and multicenter studies are needed to evaluate this observation.