Value of systematic mediastinal lymph node dissection during pulmonary metastasectomy

Systematic mediastinal lymph node dissection is the accepted standard when curative resection of bronchial carcinoma is performed. However, mediastinal lymph node dissection is not routinely performed with pulmonary metastasectomy, in which only enlarged or suspicious lymph nodes are removed. The incidence of malignant infiltration of mediastinal lymph nodes in patients with pulmonary metastases is not known.

Sixty-three patients who underwent 71 resections through a thoracotomy for pulmonary metastases of different primary tumors were studied prospectively. Selected patients showed no evidence of tumor progression or extrathoracic metastases and pulmonary metastasectomy was planned with curative intent. All patients underwent preoperative helical computed tomography (CT) scanning. Only patients with no evidence of suspicious mediastinal lymph nodes on the CT scan (less than 1 cm in the short axis) were included in this study. A mediastinal lymph node dissection was performed routinely with metastasectomy.

In 9 patients (14.3%) at least one mediastinal lymph node revealed malignant cells in accordance with the resected metastases. When compared with the preoperative CT scan, additional pulmonary metastases were detected in 16.9% of performed operations. There was a trend toward an improved survival rate in patients without involvement of the mediastinal lymph nodes. The number of pulmonary metastases had no influence on survival.

On a patient-by-patient basis, the frequency of misdiagnosed mediastinal lymph node metastases is about the same as compared with non-small cell bronchial carcinomas. Systematic mediastinal lymph node dissection reveals a significant number of patients, who otherwise are assumed free of residual tumor. The knowledge of metastases to mediastinal lymph nodes after complete resection of pulmonary metastases could influence the decision for adjuvant therapy in selected cases.