This gentleman came for routine medical check up and his chest x-ray showed a 12mm 'nodule' in the left mid zone. It has irregular margin and possibility of a malignant focus has to be strongly considered.
But is it really a pulmonary nodule? Look again carefully and study the close-up image below.
Actually, it is an old fracture of the left 7th posterior rib. The 'nodule' is callus formation. Look carefully and you will see discontinuity of the rib cortical margin. Upon further questioning, he had a history of chest trauma many years ago.