Long term follow-up for small pure ground-glass nodules: implications of determining an optimum follow-up period and high-resolution CT findings to predict the growth of nodules

Purpose To identify the optimum follow-up period for pure ground-glass nodules (GGN) measuring less than 15 mm in diameter, and to evaluate whether the initial HRCT findings can be used as predictors for the progression of pure GGN. Materials and methods A total of 150 pure GGNs present in 111 patients were evaluated. The series of HRCT images for each GGN at the time of the initial detection, 2 years after detection, and at the final follow-up were evaluated. The HRCT findings of GGN were compared between the “increasing nodule” and “non-increasing nodule” groups. Results Most (87.3%) pure GGN did not increase whereas some nodules (12.7%) eventually increased after long-term follow-up (mean 66.0 ± 25.0 months). Six (31.6%) out of the 19 increasing nodules were regarded as stable at the 2 year follow-up examination. Some morphological findings on initial HRCT, including a size greater than 10 mm ( p = 0.001), lobulated margins ( p = 0.015), and a bubble-like appearance ( p = 0.002), were significantly associated with the growth of pure GGNs. Conclusion More than 2 years of follow-up are necessary to detect the growth of pure GGNs. Some characteristic findings indicated a high likelihood of future growth of the GGN.