Have a patient that has presented with pneumonia multiple times over the past 3-6 months? Was this confirmed by chest xray? Do symptoms improve and then return? Then you need to seriously consider including lung cancer in your differential.
Sometimes lung cancer can present as a recurrent pneumonia due to mass blocking bronchioles.
If you have a patient who has presented with pneumonia multiple times over the past 3-6 months, then you need to consider ordering a CT scan of their chest. You could very well save their life if the lung carcinoma is caught early enough!