From the Guidelines
A 4mm perifissural nodule in the right lung typically does not require follow-up imaging, as perifissural nodules are commonly benign lymph nodes with characteristic triangular or oval shapes adjacent to pleural fissures, and have an extremely low likelihood of malignancy. According to the Fleischner Society guidelines, as described in the study by 1, perifissural nodules are thought to represent intrapulmonary lymph nodes, and when small nodules have a perifissural or other juxtapleural location and a morphology consistent with an intrapulmonary lymph node, follow-up CT is not recommended, even if the average dimension exceeds 6 mm. The study by 2 also supports this, stating that for incidental indeterminate pulmonary nodules measuring <6 mm on chest CT, Fleischner Society guidelines do not recommend routine follow-up given the likelihood of malignancy is <1%. However, if the nodule has atypical features (irregular margins, non-triangular shape, or location away from a fissure), then follow-up CT in 12 months might be considered, especially in high-risk patients (smokers, older age, family history of lung cancer). Key factors to consider in the decision for follow-up include:
- Nodule size and morphology
- Location and proximity to pleural fissures
- Presence of suspicious imaging features, such as spiculated borders or displacement of adjacent fissures
- Patient's clinical risk factors, including smoking history, age, and family history of lung cancer
- Use of low-dose CT technique and contiguous thin sections (1.5 mm) for follow-up imaging, as recommended by 2.
From the Research
Evaluation of 4mm Perifissural Nodule
- A 4mm perifissural nodule in the right lung is a common finding, and its malignancy potential is considered low 3, 4, 5.
- According to the Fleischner Society guidelines, review imaging may be considered in further evaluation, if clinically appropriate 6.
- Studies have shown that perifissural nodules (PFNs) are frequently found on CT scans, and they can show growth rates similar to malignant nodules, but none of the PFNs in these studies turned out to be malignant 3, 4, 5.
- The mean size of PFNs is typically small, ranging from 2.8-10.6 mm, with a mean volume of 43 mm3 3.
- Recognition of PFNs can reduce the number of follow-up examinations required for the workup of suspicious nodules 3.
Follow-up and Management
- For small (4 mm or less) incidentally detected nodules, follow-up CT in 3 months and 6 months would be appropriate in further evaluation 7.
- Small nodules that are stable in size for more than 365 days are unlikely to be pulmonary metastasis 7.
- The updated Fleischner Society guidelines emphasize the importance of morphologic features, accurate nodule measurements, and recognition of subsolid components in managing incidental pulmonary nodules 6.
- Individualized management of pulmonary nodules is encouraged, taking into account patient risk factors and nodule characteristics 6.