How Long Should Small Lung Lesions of Ground-Glass Opacity be Followed?

Introduction: Pulmonary ground-glass nodules are frequently encountered. The purpose of this study was to evaluate the natural history of them and to gain some insights on how to follow them up. Methods: We retrospectively studied patients with pulmonary nodules that met the following criteria: (1) tumor diameter of 3 cm or less, (2) ground-glass opacity proportion of 50% or more, and (3) observation without treatment for 6 months or more. Between 1999 and 2012, 108 pulmonary lesions in 61 patients fulfilled these criteria. We reevaluated their computed tomography images and analyzed changes in their size. Results: The tumors were 1 cm or lesser in size in 69 lesions, 1.1 cm to 2 cm in 34, and 2.1 cm to 3 cm in five. The proportion of solid lesions was 0% for 82 lesions, 1% to 25% for 19, and 26% to 50 % for seven. At the median observation period of 4.2 years, 29 lesions had become larger, whereas the remaining 79 had persisted without changing in size (+/- 1 mm). The median size change in the nodules that grew was 7 mm (range, 2-32 mm). All 29 tumors began to grow within 3 years of their first observation: 1 year or lesser in 13 lesions, after 1.1 years to 2 years in 12, and after 2.1 years to 3 years in four. Conclusions: Some small lung lesions exhibiting ground-glass opacity persisted without changes in size, whereas others grew gradually. The tendency to grow was clear within the first 3 years in all cases. Therefore, we conclude that these lesions should be followed for at least 3 years.