A solitary or single nodule in lung area (sub-pleural) can be carcinoid syndrome, tuberculosis, sarcoidosis, hematoma, hamartomas, chondromas, pneumonia
, lymphoma or cancer.
A well defined opacity
can be due to pneumonia
, 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.