Incidental findings occur in 15% to 30% of all diagnostic scans and in 20% to 40% of CT scans.1 Detection of these secondary abnormalities leads to clinician and patient anxiety, with surveys indicating that practitioners fall into costly and burdensome cascades of care.2 Pulmonary nodules are common incidental findings, and the introduction of low-dose CT (LDCT) screening has further increased incidence of lung nodule recognition. Subsolid pulmonary nodules pose distinct diagnostic and treatment dilemmas.
Challenges
Compared to solid lesions, subsolid nodules are less PET avid, grow slower, and have lower rates of diagnostic yield on biopsy.2 Most are low-grade adenocarcinomas with excellent long-term survival.3 A recent retrospective review demonstrated noninferiority of observation vs surgery in patients with subsolid nodules ≤2 cm and consolidation to tumor ratios of ≤0.25. Both resulted in five-year event-free survival rates of 99% to 100%.4 Thus, patients and clinicians are in a difficult position, since persistent subsolid nodules are often on the adenocarcinoma spectrum, yet aggressive management strategies may increase complication risk without improving cancer-related survival. Given the complexity of care, multiple professional societies have published recommendations to guide clinical decision-making for subsolid nodules.
Reviewing the guidelines
The Fleischner Society, National Comprehensive Cancer Network (NCCN), CHEST, American College of Radiology (ACR), and American Association for Thoracic Surgery (AATS) all stratify management by size, number, solid component, and incidental vs screening detected findings.5–10 To guide clinical decision-making, we will summarize the available guidelines.
For solitary ground-glass nodules (GGN) <6 mm, most societies recommend surveillance with annual LDCT scans or no further work-up. Solitary GGN ≥6 mm require CT scans in six to 12 months and then CT scans every 12 to 24 months. CHEST, however, recommends a 5-mm size threshold. No further follow-up is needed for solitary GGN <5 mm, while annual CT scans over at least three years are recommended for GGN ≥5 mm.
Guidelines for solitary part-solid nodules (PSN) are more heterogeneous. PSN <6 mm warrant annual LDCT scans or no further follow-up. For PSN size ≥6 mm, NCCN, Fleischner, and ACR substratify recommendations by the size of the solid component, while CHEST takes overall size and proportion of solidity (ie, >50% or <50% ground-glass component) into account; AATS uses both criteria. For overall PSN size ≥6 mm with solid component size <6 mm, NCCN, Fleischner, and ACR all advise a CT scan in three to six months followed by annual CT scans.
For solid components measuring 6 to 8 mm, a three- to six-month follow-up CT scan, PET/CT scan, biopsy, or resection is recommended. NCCN suggests a CT scan in three to six months, consideration of PET/CT scan or biopsy for incidental nodules, and three-month LDCT or PET/CT scan for screening-detected nodules. ACR advises a repeat CT scan in three months, while the Fleischner Society recommends a LDCT scan in three to six months or PET/CT, biopsy, or resection for suspicious findings. When overall size measures 6 to 8 mm, AATS suggests a CT scan in three to six months, with shorter follow-up for lesions that are >50% solid or have a solid component ≥6 mm. CHEST suggests a CT scan at three, 12, and 24 months followed by annual CT scans for all nodules with overall size ≤8 mm.
For solid components ≥8 mm, NCCN and Fleischner Society guidelines remain the same as for incidental nodules. For screening-detected nodules, NCCN and ACR recommend diagnostic CT or PET/CT scans with tissue sampling in patients at high risk. AATS recommends short-interval CT scan follow-up, biopsy, or resection for overall nodule size ≥8 mm and solid component size ≥6 mm. CHEST advises CT scan at three months followed by PET/CT scan, biopsy, or resection for persistent lesions whenever overall size measures >8 mm. Finally, multiple nodule management is guided by the most suspicious nodule.
Real-world practice
If not already clear, the heterogeneity of guidelines is likely a contributing factor to the discrepancy between published recommendations and real-world practice. Studies indicate that only 38% to 55% of patients with pulmonary nodules receive care concordant with established guidelines.2,11,12 Clinical decision-making would greatly benefit from additional risk stratification and prediction tools. Artificial intelligence, novel biomarkers, decision support tools, and multidisciplinary tumor board evaluation have all been proposed as ways to improve guideline adherence.2
Despite differences in size thresholds and surveillance timing, however, most societies still follow the same general trends, prioritizing nodule size, development of solid component, and change over time as thresholds for additional evaluation. The most practical approach is to standardize care based on the recommendations of a single society and then consistently apply guidelines to maintain evidence-based practice.
References
1. Davenport MS. Incidental findings and low-value care. Am J Roentgenol. 2023;221(1):117-123. doi:10.2214/AJR.22.28926
2. Mazzone PJ, Lam L. Evaluating the patient with a pulmonary nodule: a review. JAMA. 2022;327(3):264-273. doi:10.1001/jama.2021.24287
3. Bader JM, Prince SR, de Santis W, et al. Natural history, treatment, survival, and causes of mortality in patients with subsolid and ground-glass nodules. Chest. 2026:S0012-3692(26)00642-2. doi:10.1016/j.chest.2026.04.053
4. Li F, Qi L, Xia C, et al. Pulmonary subsolid nodules: upfront surgery or watchful waiting? Chest. 2025;167(6):1764-1777. doi:10.1016/j.chest.2024.12.028
5. MacMahon H, Naidich DP, Goo JM, et al. Guidelines for management of incidental pulmonary nodules detected on CT images: from the Fleischner Society 2017. Radiology. 2017;284(1):228-243. doi:10.1148/radiol.2017161659
6. National Comprehensive Cancer Network. NCCN Clinical Practice Guidelines in Oncology: Lung Cancer Screening. Version 1.2026. Published 2025.
7. National Comprehensive Cancer Network. NCCN Clinical Practice Guidelines in Oncology: Non-Small Cell Lung Cancer. Version 6.2026. Published 2026.
8. American College of Radiology Committee on Lung-RADS Assessment Categories 2022. Published 2022.
9. Chen H, Kim AW, Hsin M, et al. The 2023 American Association for Thoracic Surgery (AATS) expert consensus document: management of subsolid lung nodules. J Thorac Cardiovasc Surg. 2024;168(3):631-647.e11. doi:10.1016/j.jtcvs.2024.02.026
10. Gould MK, Donington J, Lynch WR, et al. Evaluation of individuals with pulmonary nodules: when is it lung cancer?: diagnosis and management of lung cancer, 3rd ed: American College of Chest Physicians evidence-based clinical practice guidelines. Chest. 2013;143(5):e93S-e120S. doi:10.1378/chest.12-2351
11. Farjah F, Monsell SE, Gould MK, et al. Association of the intensity of diagnostic evaluation with outcomes in incidentally detected lung nodules. JAMA Intern Med. 2021;181(4):480-489. doi:10.1001/jamainternmed.2020.8250
12. Abrahams JM, Creekmur B, Lee JS, Amy Liu IL, Macias M, Gould MK. Neighborhood-level socioeconomic disadvantage and adherence to guidelines for the evaluation of patients with incidentally detected pulmonary nodules. Chest. 2025;167(5):1497-1508. doi:10.1016/j.chest.2024.12.011
