A solitary or single nodule in lung area (sub-pleural) can be carcinoid syndrome, tuberculosis, sarcoidosis, hematoma, hamartomas, chon
ia, lymphoma or cancer.
If the opacity
is well defined, it can be due to pneum<span style = 'background-color: #dae8f4'>on</span>ia
, cancer, tuberculosis, a benign lung
nodule, or due to an infarct. Less well defined or diffuse opacities are usually multiple in nature and often due to inflammation
, tuberculosis (military type), asbestosis, silicosis, auto-immune diseases etc.