Ground glass opacities: Imaging, pathology, and gene mutations

Lung cancer can be detected in its early stages with computed tomography (CT). Early lung adenocarcinoma often is displayed as ground glass opacity (GGO), an entity that has been well studied over the past decade. However, few studies have focused on the correlation between CT characteristics and pathologic subtype of GGO. We aimed to explore the correlation between CT characteristics, pathologic subtype, and gene mutation associated with GGO in an effort to aid in the treatment of lung adenocarcinoma.

In this retrospective study, patients with GGO who underwent surgery in our institution between 2013 and 2016 were included. Patients were divided into 2 groups on the basis of CT characteristics: group 1, diameter <20 mm and solid component <50%; and group 2, diameter ≥20 mm or solid component ≥50%. Differences in pathologic subtype and gene mutation pattern between groups were compared using the χ² test. The correlation between pathologic subtype and epidermal growth factor receptor (EGFR) mutation was also tested using the χ² test.

A total of 1018 cases (408 in group 1, 610 in group 2) were included; of these, 544 were tested for the EGFR gene mutation. There was a significant difference in predominant subtype (P < .001) and all included subtypes (P = .044) between the groups. Of 59 cases with the pathologic subtype of micropapillary or solid, 57 were in group 2. The EGFR gene mutation rate was significantly higher in group 2 than group 1 (P < .001) and significantly correlated with pathologic subtype (P < .001); adenocarcinoma in situ was the lowest (31.4%) and papillary was the highest (85.7%). EGFR mutation subtype did not significantly differ between groups (P = .499).

CT characteristics of GGO significantly correlated with pathologic subtype and gene mutation rate. The EGFR mutation rate differed significantly among pathologic subtypes. GGOs with a diameter of <20 mm and with a solid component <50% seldom contain subtypes with poor prognosis (micropapillary and solid) and the EGFR mutation rate was significantly lower.