A focal pure ground-glass opacity (GGO) is defined on HRCT as an area of homogeneously increased opacity of the lung without a solid component and with preservation of the underlying bronchial and vascular margins.
One or more of these focal pure ground-glass opacities are often seen in the lungs, sometimes in more than one lobe, in addition to the primary lung cancer. These can represent neoplastic lesions (e.g., atypical adenomatous hyperplasia, bronchioloalveolar carcinoma, lymphoma, and even metastases) or inflammatory lesions and fibrosis.
Most focal pure ground-glass opacities associated with lung cancer do not change in size during follow-up. In addition, the prognosis of patients with a primary lung cancer and coexisting atypical adenomatous hyperplasia or bronchoalveolar carcinoma is related more to the primary lung cancer than the atypical adenomatous hyperplasia or bronchoalveolar carcinoma. Therefore, it has been suggested that therapy be directed at resection of the primary tumor without intervention in the remaining focal pure ground-glass opacities.
The case above is from a patient with a resected primary lung carcinoma and with multiple focal pure ground-glass opacities (pink arrows). These had not changed in size over a 4-year period. A more solid lesion (blue arrow) had mild FDG avidity (not shown) and had grown slightly in the same interval.