Cystic and Cavitary Lung Cancer: Its Characteristic Features on CT and FDG-PET Scans

Background: Cystic and cavitary lung cancer (CCLC) is infrequently observed on computed tomography (CT) scans; however, its diagnosis is often overlooked or delayed. Objectives: The current study aimed to investigate the CT and 18F-fluorodeoxyglucose positron emission tomography (18F-FDG PET) features of CCLC. Patients and Methods: A total of 809 patients who underwent lung tumor resection were examined in this study, and the presence of cystic and cavitary lesions on CT scans was investigated. Based on the CT scans, CCLC was identified in 102 consecutive patients. The diameters of the whole nodule and the airspace portion of the lesion, morphological patterns of cystic and cavitary lesions, presence of ground glass opacity (GGO), and loculation pattern (including the presence of a septum) were evaluated. The positron emission tomography (PET) scans of CCLC were also assessed visually and semi-quantitatively. Results: A total of 104 CCLC lesions were evaluated in this study. The histological analysis indicated 85 cases of adenocarcinoma (AD) and 19 cases of squamous cell carcinoma (SCC). The morphological patterns of cystic and cavitary lesions were classified into four types. The presence of GGO, type 4 morphological pattern (a soft-tissue-density structure intermixed within clusters of a cavitary lesion), and multilocular with septum (MS) loculation pattern were significantly different according to the histological type. The maximum standardized uptake value (SUVmax) on PET scans was significantly lower in AD compared to SCC (P = 0.002). In the solid nodule part of cystic and cavitary lesions, the MS pattern was significantly more common in AD (P = 0.044). Conclusion: When cystic and cavitary lesions are observed on CT scans, the presence of GGO and the MS pattern should be considered, as it may help differentiate the histological findings.