Subsolid Pulmonary Nodules
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This pathway provides guidance on the imaging surveillance of adult patients with subsolid pulmonary nodules.
This pathway is based on guidelines that do not apply to patients younger than 35 years, immunocompromised patients or patients with cancer.
Date reviewed: March 2017
Date of next review: August 2023
Published: November 2017
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- A pulmonary nodule is radiologically defined as an opacity
- Nodule size has a clear relationship with risk of malignancy,
- A subsolid nodule/ground glass nodule is defined as a focal area of slightly increased CT attenuation through which the normal lung parenchyma structures, airways, and vessels are visually preserved.
- Subsolid nodules are radiologically divided into pure ground glass nodules and part-solid ground glass nodules.
- Subsolid nodules tend to have a slow growth rate with volume doubling times (VDTs) ≥400 days and therefore longer total follow-up periods are recommended for subsolid nodules compared to solid nodules.
- This pathway presents an approach to the investigation and management of subsolid pulmonary nodules based on the current guidelines.
- Risk factors such as smoking history, familial history of lung cancer or exposure to carcinogenic agents are not considered in the current guidelines due to a lack of sufficient data.
- Several image-guided biopsy techniques are available and the choice depends on local expertise, availability, location of nodule and patient preferences
- A pulmonary nodule is radiologically defined as an intra-parenchymal rounded or irregular opacity less than 3cm in diameter and not associated with atelectasis or lymphadenopathy. Lesions that are larger than this are generally referred to as masses and are more likely to be malignant 1
- Pulmonary nodules can be further classified according to their attenuation on computed tomography (CT). A solid nodule has homogenous soft-tissue attenuation. Subsolid nodules include pure ground-glass nodules (focal area of hazy increased attenuation through which bronchovascular margins can be visualised) and part-solid nodules (consisting of both solid soft-tissue attenuation and ground-glass components) 1
- The widespread use of multi-detector CT has made it commonplace to detect pulmonary nodules often when they are sub centimetre in size. Nodules may be detected incidentally (on chest radiographs, chest CT or imaging for other purposes) or in some countries, through lung screening programs. The majority of these nodules have a benign aetiology but a small proportion represent malignancy and if detected early, may be cured
- The primary aim of investigation is to determine which nodules are malignant early whilst minimising patient exposure to ionising radiation and limiting the number of unnecessary invasive procedures
- This pathway presents an evidence-based and consensus-based approach to the investigation and management of subsolid pulmonary nodules
- Distinguishing solid from subsolid features is an essential step in the evaluation of pulmonary nodules 2
- Subsolid nodules (SSN), also referred to as ground glass nodules (GGN), are defined as a circumscribed area of increased lung attenuation with preservation of the bronchial and vascular margins 3
- An SSN can be a part-solid GGN (part of the nodule completely obscures the underlying lung parenchyma) or a pure GGN (no completely obscured areas) 4-6
- Pulmonary subsolid nodules have a high likelihood of malignancy, but are often indolent and caused by inflammation, infection, or fibrosis 5, 7, 8
- Although transient SSNs can represent a large range of benign diseases, persistent SSNs have a high likelihood of malignancy, with reported malignancy rates ranging from 19.4% to 75%. (9) These malignancy rates are much higher than the likelihood of malignancy of solid pulmonary nodules (34% for pure ground glass and 63% for part-solid compared to only 7% for solid nodules 10, 11
- Since SSNs usually have a slow growth rate with a high likelihood of malignancy, follow-up guidelines for solid pulmonary nodules are not appropriate for SSNs 5, 6
Pure Ground Glass Nodule
- Pure Ground Glass Nodules are defined as focal nodular areas of increased lung attenuation through which lung parenchymal structures, such as the pulmonary vessels or bronchial structures, can be observed 3, 12
Part Solid Nodule
- Part solid nodules are nodules that present with both ground-glass and solid components in which the underlying lung architecture cannot be visualized 11
- The solid component may represent the invasive foci of adenocarcinomas although other histologic changes, such as alveolar collapse, inflammation and fibrosis may also appear as a solid region of SSNs on CT 11, 13
- Since the management plan for part-solid GGNs is determined by the size of the solid portion, it is important that both the solid component size as well as the total tumour size is reported 11, 14
Thin Section Computed Tomography (CT)
- CT with the thinnest slices possible is the initial investigation of choice for the evaluation of pulmonary nodules 12, 15, 16
- The ground glass component should be evaluated on the lung window with an edge-enhancing (sharp) filter to judge the presence and extent of solid components 6
- It can distinguish true lung nodules from lesions of the chest wall, pleura and imaging artefact 17
- It can identify features that suggest a benign or malignant process such as
- Ground-glass lesions that are ≤6 mm in diameter usually represent atypical alveolar hyperplasia
- Ground-glass lesions that are between 5 and 10 mm in diameter are suspicious for bronchioloalveolar carcinoma
- Part solid lesions may represent the mixed subtype of adenocarcinoma, also called minimally invasive adenocarcinoma 18, 19
- Surveillance strategies utilising CT have been developed for the follow-up of patients with low risk pulmonary nodules. 15, 16, 20 Five years of radiographic stability on surveillance CT strongly suggest that the lesion is benign, obviating long-term surveillance 6, 21
Positron Emission Tomography / Computed Tomography (PET / CT)
- Studies have also shown that the use of PET/CT to discriminate between benign and malignant subsolid nodules to be inappropriate 22
- PET/CT is of limited value and even potentially misleading for pure ground glass nodules (GGN) as small pure GGNs are usually negative at PET 3
- The Fleischner Society only recommend considering PET-CT for nodules with particularly suspicious morphology (ie, lobulated margins or cystic components), a growing solid component, or a solid component larger than 8 mm 3, 5, 6
Date of literature search: February 2017
References are graded from Level I to V according to the Oxford Centre for Evidence-Based Medicine, Levels of Evidence. Download the document
- Hansell DM, Bankier AA, MacMahon H, McLoud TC, Muller NL, Remy J. Fleischner Society: glossary of terms for thoracic imaging. Radiology. 2008;246(3):697-722. (Guidelines). View the reference
- Cha MJ, Lee KS, Kim HS, Lee SW, Jeong CJ, Kim EY, et al. Improvement in imaging diagnosis technique and modalities for solitary pulmonary nodules: from ground-glass opacity nodules to part-solid and solid nodules Expert Rev Respir Med. 2016;10(3):261-78. (Review article). View the reference
- Naidich DP, Bankier AA, MacMahon H, Schaefer-Prokop CM, Pistolesi M, Goo JM, et al. Recommendations for the management of subsolid pulmonary nodules detected at CT: a statement from the Fleischner Society. Radiology. 2013;266(1):304-17. (Guidelines). View the reference
- Heuvelmans MA, Oudkerk M. Management of subsolid pulmonary nodules in CT lung cancer screening. J Thorac Dis. 2015;7(7):1103-6. (Review article). View the reference
- Scholten ET, de Jong PA, de Hoop B, van Klaveren R, van Amelsvoort-van de Vorst S, Oudkerk M, et al. Towards a close computed tomography monitoring approach for screen detected subsolid pulmonary nodules? Eur Respir J. 2015;45(3):765-73. (Level I evidence). View the reference
- MacMahon H, Naidich DP, Goo JM, Lee KS, Leung AN, Mayo JR, et al. Guidelines for Management of Incidental Pulmonary Nodules Detected on CT Images: From the Fleischner Society 2017. Radiology. 2017:1-16. (Guidelines). View the reference
- Suzuki K, Asamura H, Kusumoto M, Kondo H, Tsuchiya R. "Early" peripheral lung cancer: prognostic significance of ground glass opacity on thin-section computed tomographic scan. Ann Thorac Surg. 2002;74(5):1635-9. (Level II evidence). View the reference
- Vazquez M, Carter D, Brambilla E, Gazdar A, Noguchi M, Travis WD, et al. Solitary and multiple resected adenocarcinomas after CT screening for lung cancer: histopathologic features and their prognostic implications. Lung Cancer. 2009;64(2):148-54. (Level II/III evidence). View the reference
- Oh JY, Kwon SY, Yoon HI, Lee SM, Yim JJ, Lee JH, et al. Clinical significance of a solitary ground-glass opacity (GGO) lesion of the lung detected by chest CT. Lung Cancer. 2007;55(1):67-73. (Level II evidence). View the reference
- Henschke CI, Yankelevitz DF, Mirtcheva R, McGuinness G, McCauley D, Miettinen OS. CT screening for lung cancer: frequency and significance of part-solid and nonsolid nodules. AJR Am J Roentgenol. 2002;178(5):1053-7. (Level II evidence). View the reference
- Kim H, Park CM, Koh JM, Lee SM, Goo JM. Pulmonary subsolid nodules: what radiologists need to know about the imaging features and management strategy. Diagn Interv Radiol. 2014;20(1):47-57. (Review article). View the reference
- Park CM, Goo JM, Lee HJ, Lee CH, Chung DH, Chun EJ, et al. Focal interstitial fibrosis manifesting as nodular ground-glass opacity: thin-section CT findings. Eur Radiol. 2007;17(9):2325-31. (Level III evidence). View the reference
- Austin JH, Garg K, Aberle D, Yankelevitz D, Kuriyama K, Lee HJ, et al. Radiologic implications of the 2011 classification of adenocarcinoma of the lung. Radiology. 2013;266(1):62-71. (Review article). View the reference
- Travis WD, Brambilla E, Noguchi M, Nicholson AG, Geisinger KR, Yatabe Y, et al. International association for the study of lung cancer/american thoracic society/european respiratory society international multidisciplinary classification of lung adenocarcinoma. J Thorac Oncol. 2011;6(2):244-85. (Guidelines) View the reference
- Gould MK, Donington J, Lynch WR, Mazzone PJ, Midthun DE, Naidich DP, 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 Suppl):e93S-120S. (Guidelines). View the reference
- MacMahon H, Austin JH, Gamsu G, Herold CJ, Jett JR, Naidich DP, et al. Guidelines for management of small pulmonary nodules detected on CT scans: a statement from the Fleischner Society. Radiology. 2005;237(2):395-400. (Guidelines). View the reference
- Shaham D, Guralnik L. The solitary pulmonary nodule: radiologic considerations. Semin Ultrasound CT MR. 2000;21(2):97-115. (Review article). View the reference
- Godoy MC, Naidich DP. Subsolid pulmonary nodules and the spectrum of peripheral adenocarcinomas of the lung: recommended interim guidelines for assessment and management. Radiology. 2009;253(3):606-22. (Review article). View the reference
- Lee SM, Park CM, Goo JM, Lee CH, Lee HJ, Kim KG, et al. Transient part-solid nodules detected at screening thin-section CT for lung cancer: comparison with persistent part-solid nodules. Radiology. 2010;255(1):242-51. (Level III evidence). View the reference
- Callister ME, Baldwin DR, Akram AR, Barnard S, Cane P, Draffan J, et al. British Thoracic Society guidelines for the investigation and management of pulmonary nodules. Thorax. 2015;70 Suppl 2:ii1-ii54. (Guidelines) View the reference
- Song YS, Park CM, Park SJ, Lee SM, Jeon YK, Goo JM. Volume and mass doubling times of persistent pulmonary subsolid nodules detected in patients without known malignancy. Radiology. 2014;273(1):276-84. (Level III evidence). View the reference
- Veronesi G, Travaini LL, Maisonneuve P, Rampinelli C, Bertolotti R, Spaggiari L, et al. Positron emission tomography in the diagnostic work-up of screening-detected lung nodules. Eur Respir J. 2015;45(2):501-10. (Review article). View the reference
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