Spontaneous regression of pulmonary pure ground-glass opacity with progression of a solid component during a 40-month follow-up

A 75-year-old man with a 50 pack-year smoking history underwent a right upper lobectomy due to an early stage lung adenocarcinoma. Simultaneously, pure ground-glass opacity (GGO) on the left upper lobe measuring 6.7 mm in diameter was detected on computed tomography (CT), which was considered atypical adenomatous hyperplasia, a bronchioloalveolar carcinoma, or focal organizing pneumonia/fibrosis. Eighteen months later, the diameter of the lesion increased to 9.0 mm. The lesion further enlarged to 10.4 mm with a small solid component within the GGO at 28 months after the initial CT scan. At the 33- month follow-up, the lesion had decreased in size and a solid component was prominent. Forty months after the initial CT, the lesion seemed to be a fibrotic scar. To the best of our knowledge, no studies have reported a pure GGO progressing with a solid component that regressed spontaneously over such a long period. Although this case seems rare, physicians should be aware that a lung nodule compatible with progression from in situ carcinoma to invasive carcinoma on CT could resolve over 24 months.