Lung cancer patients with a previous extra-pulmonary malignancy should not be considered homogeneous: a clinicopathological analysis of 3530 surgical cases

Background Lung cancer patients with a previous extra-pulmonary malignancy have been widely discussed for their postoperative prognosis. Still, whether different types of previous extra-pulmonary malignancy confer different clinicopathological features and outcomes of lung cancer patients deserves further investigation. Methods The medical records of patients undergoing operation for pulmonary malignancy were retrospectively reviewed. After identifying primary lung cancer out of pulmonary metastasis in patients with a history of previous extra-pulmonary malignancy, clinicopathological parameters and postoperative prognosis were compared between lung cancer patients without and with different types of previous extra-pulmonary malignancy. Results Approximately, 5.0% lung cancer patients undergoing surgery had a previous extra-pulmonary malignancy. Prior breast cancer (20%) and colorectal cancer (16%) formed the majority of these previous extra-pulmonary malignancies. Many clinicopathological features such as reason for visit, tumor size and histological subtype were significantly different between lung cancer patients without and with different types of previous extra-pulmonary malignancy ( P < 0.05). Lung cancer patients with a previous occurrence of breast cancer were the most different type from patients without a previous extra-pulmonary malignancy in clinicopathological features ( P < 0.05). The postoperative overall survival was not significantly different between lung cancer patients without and with different types of previous extra-pulmonary malignancy ( P > 0.05). Conclusion Previous extra-pulmonary malignancy was confirmed to be harmless to postoperative prognosis of lung cancer patients. Lung cancer patients with a previous extra-pulmonary malignancy, especially with a previous occurrence of breast cancer, were highly heterogeneous in clinicopathological features. These findings implied there might be a unique etiology existing in lung cancer following a previous occurrence of breast cancer.