How long should small lung lesions of ground-glass opacity be followed?

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.

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.

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.

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.