The interpretation depends on what is meant by 'alveolar opacities'. In all likelihood the radiologist is referring to mild airspace infiltrates that are seen as shadows. Unfortunately this is a non specific abnormality, but probably an abnormality rather than a normal variant. It would be wise to get a CT scan to further, better characterize these infiltrates which might, on a CT scan, suggest a specific disease or class of diseases. Following the CT scan, the radiologist and a pulmonologist should review the findings and then give you their best assessment of what is going on and whether a lung biopsy or ongoing observation is indicated. This is not a black and white situation. Each of these specialists will have to bring his experience to bear on the interpretation and subsequent recommendations.