CT findings of minimally invasive adenocarcinoma (MIA) of the lung and comparison of solid portion measurement methods at CT in 52 patients.

OBJECTIVES

We aimed to retrospectively investigate CT findings of minimally invasive adenocarcinoma (MIA) and to determine the appropriate method for measurement of solid portions in MIAs at CT.

METHODS

From May 2012 to April 2014, 55 pulmonary nodules in 52 patients were pathologically confirmed as MIAs and were included in this study. CT findings of MIAs and measurements of solid portions at CT were evaluated by two independent radiologists.

RESULTS

Mean size of MIAs was 10.5 mm ± 4.8 (range, 4-28 mm). Fifty-two MIAs manifested as 28 pure ground glass nodules (GGNs) (53.8 % %), 22 part-solid GGNs (42.3 % %), and 2 two solid nodules (3.8 % %) at CT. Lobulated border, bubble lucency, and pleural retraction were frequently found in both observers (26.9-42.3 % %). Differences according to window settings between solid portion size and invasive component size were not significantly different in both observers (p > 0.05). As for interobserver agreement, 95 % CIs for solid portion size in the mediastinal window setting (-2.2 to 3.4; mean, 0.6) were slightly narrower than those in the lung window setting (-2.6 to 3.1; mean, 0.3).

CONCLUSIONS

Nearly all MIAs appear as pure and part-solid GGNs. Mediastinal and lung window settings can be applied for measurement of solid portions at CT without a significant difference.

KEY POINTS

• Nearly all MIAs appear as pure and part-solid GGNs. • MIAs show frequent interval growth at follow-up. • MIAs with solid portion ≥5 mm ranged from 7.7 % to 19.2 %. • Mediastinal and lung window settings can be applied for solid portion measurement.