Ground-glass opacity nodules: histopathology, imaging evaluation, and clinical implications

Ground-glass opacity (GGO) nodules noted at thin-section computed tomography (CT) scan have been shown to have a histopathologic relationship with atypical adenomatous hyperplasia, bronchioloalveolar carcinoma (BAC, or adenocarcinoma in situ), and adenocarcinoma with a predominant BAC component (minimally invasive adenocarcinoma). Patients harboring GGO nodules of BAC or adenocarcinoma with a predominant BAC component demonstrate negative results for malignancy at positron emission tomography. In peripheral adenocarcinoma of a part-solid (mixed GGO and solid attenuation) nodular nature, both the degree of disappearance of GGO area, when the lung window is changed to a mediastinal window image at CT scanning, and the maximum standardized uptake value at positron emission tomography correlate well with histopathologic BAC and non-BAC ratios. However, a high non-BAC ratio appears to be the only independent prognosis-determining factor. Epidermal growth factor receptor mutations are positively correlated with the GGO ratio at a thin-section CT scan in lung adenocarcinomas. As patients with a GGO nodule of BAC or adenocarcinoma with a predominant BAC component have a good prognosis, a wedge resection is recommended as a treatment option, in preference to lobectomy. Even for multiple malignant pure GGO nodules, minimally invasive surgery (including multiple resections) with the preservation of lung volume and adequate imaging follow-up studies are the recommended diagnostic and therapeutic measures.