Pulmonary nodules are described according to their radiographic appearance as solid or subsolid. Subsolid nodules are subclassified into part-solid nodules and pure ground-glass nodules. This morphological classification is central to clinical decision making because nodule type correlates with growth behavior and the probability of malignancy. The distinctions between solid and subsolid appearance guide choices about surveillance intervals, diagnostic testing, and interventions.
When prior imaging studies are available, comparison with the current scan is essential. Demonstration of interval stability or growth on serial imaging provides critical information about the likelihood that a nodule is malignant. Prior studies may allow clinicians to avoid unnecessary procedures when a lesion has been stable, or to expedite diagnostic workup when there is documented enlargement. The presence or emergence of a solid component in a previously subsolid lesion is particularly important to identify on serial imaging.
Different nodule types have different stability thresholds that are used to infer benignity. Solid nodules that have been radiographically stable for 2 years are generally considered benign. By contrast, subsolid nodules require a longer period of documented stability before they can be considered benign, reflecting their typically slower growth patterns and different natural history. The review underscores that the time frame for declaring benignity is longer for subsolid lesions than for solid lesions.
Prediction models are available to stratify the risk that a pulmonary nodule is malignant. These models are used to guide the management of solid nodules, helping clinicians decide which patients should undergo surveillance imaging, further noninvasive testing, biopsy, or resection. The use of validated risk calculators forms part of an evidence-informed approach to nodule management and assists in matching the intensity of diagnostic evaluation to the estimated probability of cancer.
Management is typically stratified by estimated risk of malignancy. For nodules assessed as low risk, CT surveillance is indicated to monitor for interval change. Intermediate-risk nodules are candidates for further noninvasive evaluation with positron-emission tomography–CT (PET-CT), tissue sampling via biopsy, or both. Selected nodules judged to be high risk may proceed to surgical resection for definitive diagnosis and treatment. The review emphasizes tailoring the approach to the individual patient based on nodule characteristics and clinical context.
Although subsolid nodules characteristically grow more slowly than solid nodules, they are associated with a higher risk of being malignant. The risk increases particularly when a solid component develops within a subsolid lesion or when an existing solid component progressively enlarges. Because of this behavior, subsolid nodules often require longer-term follow-up and careful assessment of any evolution in their radiographic appearance.
When tissue diagnosis is indicated, the review describes available biopsy methods, including transthoracic needle biopsy and navigational bronchoscopy. Choice of biopsy technique depends on lesion location, size, patient factors, and local expertise. Procedural considerations include diagnostic yield and the balance of potential benefit versus procedural risk.
The optimal management strategy seeks to balance timely diagnosis for persons who have cancer against avoidance of unnecessary invasive procedures in persons who have benign disease. This balance relies on accurate risk stratification, appropriate use of imaging and prediction tools, prudent selection of biopsy techniques, and individualized decision making that accounts for nodule type (solid versus subsolid), growth behavior, and patient preferences.
Pulmonary nodules are a common clinical problem that require structured assessment: define nodule type, compare with prior imaging, estimate malignancy risk using prediction models where applicable, and select an appropriate management pathway—CT surveillance for low risk, PET-CT and/or biopsy for intermediate risk, and consideration of surgical resection for selected high-risk lesions. Subsolid nodules warrant particular attention because of their slower growth yet higher potential for malignancy, especially when a solid component emerges or enlarges. Biopsy options include transthoracic needle biopsy and navigational bronchoscopy. The goal in all cases is to achieve accurate and timely diagnosis while minimizing unnecessary invasive procedures.
Reference: Callister MEJ, Silvestri GA. Pulmonary Nodules. N Engl J Med. 2026;395(9):894-905. PMID: 42685318. DOI: 10.1056/NEJMcp2515063.