I would agree that a history of pneumonia or pleurisy is not a specific risk factor for oral cancer metastases to spread to the lungs, but the lungs are one of many distant sites that can be affected.
What is much more important, is the type of tumour, the size of the tmour, the site of the tumour, and most importantly, early diagnosis before there has been local invasion of the tissues and lymphmatic involvement.
Hope all goes well for this individual at this stressful time.