CYSTIC lung lesions are occasionally encountered during CT lung cancer screening, but their clinical significance has remained unclear due to limited data on their risk of malignancy. A recent retrospective study conducted within a large UK health network has sought to clarify this, analysing the malignancy risk and growth patterns of these lesions. A key finding of the study is that 14% of cystic lesions identified in screened patients were ultimately diagnosed as lung cancer, most commonly at early stages.
To assess malignancy risk, researchers reviewed all CT scans performed as part of a lung cancer screening programme between January 2015 and July 2023. Radiology reports were searched to identify patients with cystic lung lesions, and imaging characteristics, including lesion morphology, wall features, and presence of solid components, were recorded. All follow-up scans were reviewed to track lesion growth and complexity over time. Statistical analysis, including Kaplan-Meier survival curves, was used to assess time to growth and cancer diagnosis.
Out of 15,762 screened patients, 235 had cystic lung lesions. Of these, 33 (14%) developed lung cancer. Nodular wall thickening was significantly associated with malignancy (odds ratio [OR}: 11; p=0.002), as was the presence of a solid nodule either alone (OR: 5.3; p<0.001) or in combination with a ground-glass component (OR 24: p<0.001). In contrast, unilocular lesions without wall thickening (n = 46) showed no cases of malignancy. While multilocularity alone did not predict cancer risk (OR: 1.7; p>0.2), lesion growth or increasing complexity over time did correlate strongly with malignancy (p<0.001). The median time to lesion growth was 636 days, and the median time to cancer diagnosis was 482 days. Notably, 85% of the diagnosed cancers were at stage 0 or I.
This study highlights the importance of careful radiologic evaluation of cystic lung lesions, particularly those with nodular wall thickening or solid components. These features are associated with significantly higher malignancy risk, though most cancers presented at early stages and progressed slowly. For clinical practice, this supports a tailored follow-up strategy based on lesion characteristics, reducing unnecessary interventions for clearly benign lesions. Limitations include the retrospective design and reliance on radiology reports for case identification.
Reference
Byrne SC et al. Risk of Malignancy in Cystic Lung Lesions in a Lung Cancer CT Screening Program. Radiology. 2025;DOI: 10.1148/radiol.243166.
