Concurrence of sarcoidosis and lung cancer. A report of four cases.

Although sarcoidosis and lung cancer are both frequently encountered conditions, their simultaneous occurrence in the same patient is unusual. In this report, we describe 4 cases of their concurrence and discuss the possible pathogenic mechanisms of their concurrent appearance. In particular, in 2 of the cases, both diseases had coexisted for a long period (more than 6 and 4 years, respectively), showing a surprisingly slow growth of cancers. Although the chest computed tomography showed hilar and mediastinal lymphadenopathy, the histopathological findings of the excised lymph nodes of both cases revealed no metastasis. The causal relationship between sarcoidosis and lung cancer remains uncertain, but cases such as these may be helpful in elucidating its precise nature.