From the Guidelines
Intrapulmonary lymph nodes (IPLNs) should be considered abnormal if the long axis is more than 1.5 cm, and management should prioritize a conservative approach with serial imaging surveillance, reserving more aggressive evaluation for nodes with concerning features or significant growth. According to the revised response criteria for malignant lymphoma 1, lymph nodes with a long axis of 1.1 to 1.5 cm should only be considered abnormal if their short axis is more than 1.0 cm. The appearance of any new lesion more than 1.5 cm in any axis during or at the end of therapy should be carefully evaluated, and increased FDG uptake in a previously unaffected site should only be considered relapsed or progressive disease after confirmation with other modalities.
Key considerations in the management of IPLNs include:
- Size: Nodes with a long axis greater than 1.5 cm are considered abnormal and warrant further evaluation
- Growth: A 50% increase from nadir in the size of any previously involved node is indicative of progressive disease
- Metabolic activity: PET-CT may be useful for assessing metabolic activity in IPLNs larger than 8-10 mm
- Patient risk factors: Smoking history, prior malignancy, and other risk factors may influence the management approach
In general, small IPLNs (less than 1 cm) with typical radiographic features can be monitored with follow-up CT scans at 6-12 month intervals for the first 2 years, then annually for 3-5 years if stable 1. However, more aggressive evaluation, including shorter interval follow-up imaging or tissue sampling, is warranted for nodes with concerning features or significant growth. The management rationale balances the low probability of malignancy in typical IPLNs against the need to identify potentially cancerous lesions early, as outlined in the revised response criteria for malignant lymphoma 1.
From the Research
Intrapulmonary Lymph Node Management
- Intrapulmonary lymph nodes are a rare finding on radiological examination, but should be considered in the differential diagnosis of solitary or multiple peripheral pulmonary nodules in adults 2.
- The appearance of intrapulmonary lymph nodes on CT scans is non-specific, and follow-up CT may be useful in patients with suspected intrapulmonary lymph nodes 3.
- Intrapulmonary lymph nodes are typically located in the subpleural region, are ovoid or round, homogeneous, and well-defined, and range in diameter from 9 to 10 mm 3.
- The management of intrapulmonary lymph nodes depends on the clinical context, and may involve thoracoscopic surgery or resection if malignancy is suspected 2.
Lymphoma Diagnosis and Treatment
- Lymphoma is a group of malignant neoplasms of lymphocytes, and is traditionally classified as non-Hodgkin or Hodgkin lymphoma 4.
- The diagnosis of lymphoma typically involves an open lymph node biopsy, and the Lugano classification system is used to stage the disease 4.
- Treatment plans for lymphoma differ between the main subtypes, and may involve chemotherapy, radiotherapy, or a combination of both 4, 5.
- Rituximab-CHOP (R-CHOP) is a common treatment regimen for diffuse large B-cell lymphoma, and has been shown to be effective in patients with primary mediastinal large B-cell lymphoma 5.
CT Features of Benign Intrapulmonary Lymph Nodes
- Benign intrapulmonary lymph nodes in pediatric patients with known extrapulmonary solid malignancy are typically subcentimeter, smoothly marginated, and solid without associated calcification or fat on CT 6.
- The most common shape of benign intrapulmonary lymph nodes is triangular, and they are often located in the pleura-based, perifissural, or parenchymal regions 6.
- The CT features of benign intrapulmonary lymph nodes can be useful in distinguishing them from malignant lesions, and can help guide management decisions 6.