Initial assessment
The incidental detection of a solid pulmonary nodule is a common situation in clinical practice, particularly following computed tomography performed for other reasons. The initial approach should begin by confirming that the lesion is indeed a solid nodule and by excluding situations outside the usual scope of the recommendations, such as age under 35 years, immunosuppression, suspected active pulmonary infection, known malignancy or a lung cancer screening setting.
Risk stratification
After this initial assessment, it is essential to stratify the risk of malignancy. The main risk factors include older age, a significant smoking history, previous cancer, upper-lobe location, irregular or spiculated margins and documented nodule growth. Conversely, younger age, absence of smoking and small nodules with regular margins are associated with a lower probability of malignancy.
Nodules smaller than 6 mm
Nodule size is one of the most important factors guiding surveillance. For solid nodules smaller than 6 mm, particularly in low-risk patients, routine imaging follow-up is generally not required. In patients at increased risk, follow-up computed tomography at approximately 12 months may be considered.
Nodules measuring 6 to 8 mm
Nodules measuring between 6 and 8 mm require more structured imaging surveillance. Repeat computed tomography is generally recommended after 6 to 12 months in low-risk patients, with a further assessment at 18 to 24 months if uncertainty regarding stability persists. In higher-risk patients, the initial follow-up tends to be earlier, often after 3 to 6 months, with additional surveillance according to the subsequent course.
Nodules larger than 8 mm
For solid nodules larger than 8 mm, the probability of malignancy increases significantly. In these cases, specialist assessment should be considered, including the possibility of PET-CT, short-interval computed tomography, bronchoscopy or transthoracic biopsy, depending on the imaging characteristics, clinical context and accessibility of the lesion.
Multiple nodules
In cases of multiple pulmonary nodules, management should be based on the most suspicious or dominant nodule. Their distribution, morphology and temporal stability also contribute to clinical interpretation.
Growth and stability
Assessment of growth is particularly important. An increase of 2 mm or more may be considered clinically significant and increase suspicion of malignancy. Conversely, prolonged stability on serial imaging substantially reduces the probability of malignant disease in many cases.
Subsolid nodules
Subsolid nodules, including pure ground-glass and part-solid nodules, have different biological behaviour and should follow their own specific algorithms. For this reason, the initial distinction between a solid and a subsolid nodule is fundamental to appropriate clinical management.
