Isolated melanoma in the lung where there is no known primary site: metastatic disease or primary lung tumour?

Patients with no history of melanoma occasionally present with apparently metastatic melanoma in the lungs, but have no evidence of a primary melanoma. The aims of this study were to investigate the role of surgical resection in the treatment of such patients, and to examine the evidence for a diagnosis of primary pulmonary melanoma in each case. Patients with an unknown primary melanoma who presented with pulmonary disease and subsequently underwent surgical resection were identified from the Sydney Melanoma Unit database. Fifteen patients fulfilled the study criteria. Multiple lesions were present in four. Eight wedge resections and 10 lobectomies were performed. The patients' median survival was 32 months and the 5-year actuarial survival was 42%. This compares with the overall Sydney Melanoma Unit experience of lung resection for melanoma in 83 patients, where the median survival was 19 months and the 5-year survival was 22%. Resection of pulmonary disease in melanoma patients with an unknown primary lesion can result in long-term survival, and even apparent cure. It is possible that some of the patients in this series had primary melanoma of the lung, but this is impossible to prove.