From the Guidelines
Nodules with irregular margins are more concerning than those with regular margins.
Key Characteristics of Concerning Nodules
- Irregular margins: spiculated or lobulated margins are strongly associated with malignancy 1
- Size: larger nodules are more likely to be malignant, with nodules over 2 cm being more concerning 1
- Location: upper lobe location is more common for malignant nodules, although this is less significant in Asia due to the high prevalence of TB 1
- Cavitation: malignant lesions are associated with irregular, thicker walls 1
Assessment of Malignancy Risk
The risk of malignancy can be estimated based on nodule characteristics, patient history, and other factors.
- A model for predicting malignancy risk includes factors such as age, smoking history, history of extrathoracic cancer, nodule diameter, spiculation, and location 1
- The combination of smooth or lobulated borders, irregular shape, and solid attenuation has a negative predictive value of 86% for malignancy 1
Management of Pulmonary Nodules
The management of pulmonary nodules depends on the estimated risk of malignancy and other factors.
- For solitary solid noncalcified nodules measuring 6–8 mm, follow-up examinations are recommended at 6–12 months and again at 18–24 months 1
- For nodules larger than 8 mm, consider 3-month follow-up, work-up with combined PET and CT, tissue sampling, or a combination thereof 1
From the Research
Nodule Margin Characteristics
- Nodules with irregular margins are more concerning than those with regular margins, as they are associated with a higher likelihood of malignancy 2, 3, 4, 5
- Irregular or microlobulated margins are independently associated with malignancy in thyroid nodules with repeat nondiagnostic results 2
- Spiculated margins also suggest the presence of a malignant lesion in solitary pulmonary nodules 3
- Lobulated margins increase the likelihood that a nodule is malignant in solid non-calcified nodules larger than 50mm3 4
Comparison of Margin Characteristics
- Smooth, well-defined margins suggest a benign nodule in solitary pulmonary nodules 3
- Irregular margins may not be a significant criterion for malignancy in nodular goiters with multiple nodules grown together and without clear margins 6
- The presence of "two or more suspicious findings", including irregular margins, can be used as the cutoff for distinguishing benign and malignant nodules in thyroid nodules with repeat nondiagnostic results 2
Clinical Implications
- More careful observation, especially for lesions with irregular margins and low echogenicity, can help improve the diagnostic accuracy of thyroid ultrasonography 5
- Greater care may decrease the incidence of malignancy among thyroid nodules with low or very low suspicion patterns 5
- The American Thyroid Association recommends further fine needle aspiration cytology for nodules with high suspicion pattern, including irregular margins, depending on the pattern and the size of the nodule 6