This coin lesion or solitary pulmonary nodule (SPN) was followed up with chest radiograph for many years and was unchanged. CT was performed elsewhere at some point. Biopsy was not undertaken.
A single round lung lesion has been given the name a 'coin lesion' or in other cases a solitary pulmonary nodule. The differential is wide with benign and malignant causes. Generally, an SPN is viewed as a lung cancer until proven otherwise.
This is probably a benign lesion such as a harmatoma, but without any definite appearances.