E2204. Intrapulmonary Lymph Nodes: Typical Features and Mimics
  1. Raquelle El Alam; Brigham and Women's Hospital
  2. Mark Hammer; Brigham and Women's Hospital
  3. Suzanne Byrne; Brigham and Women's Hospital
Intrapulmonary lymph nodes are a frequent cause of incidental pulmonary nodules. Emerging data allows radiologists to confidently diagnose some of these nodules (i.e., those touching pleural surfaces) as benign, requiring no further follow-up. Other intrapulmonary lymph nodes may be suggested based on typical imaging features but still require follow-up given overlap in appearance with early lung cancer. Finally, radiologists may mistake some malignant nodules, particularly those with subpleural location or pleural tags, as benign intrapulmonary lymph nodes. Recognition of typical features and ‘red flags’ will improve radiologists’ interpretation of chest CTs, limiting false negatives and false positives for incidental pulmonary nodules.

Educational Goals / Teaching Points
Describe the typical imaging features of intrapulmonary lymph nodes. Describe ‘red flag’ features that should prompt radiologists to suggest that a subpleural nodule is not an intrapulmonary lymph node.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
Intrapulmonary lymph nodes have typical shapes and locations. The typical shapes of intrapulmonary lymph nodes include: triangular, polygonal, oval, and lenticular. The typical locations of intrapulmonary lymph nodes include: perifissural, other subpleural (e.g., costal pleura), septal connection to the pleura, or at bronchial and vascular bifurcations. Incidental pulmonary nodules with typical shape and perifissural or other subpleural locations may be confidently diagnosed as intrapulmonary lymph nodes. Incidental pulmonary nodules with typical shape and other typical locations may be suggested to represent intrapulmonary lymph nodes, but follow-up is required. ‘Red flag’ findings include subsolid density or lobulated margins. Radiologists should not suggest these nodules are intrapulmonary lymph nodes. Radiologists should exercise caution about perifissural nodules in patients with history of malignancy that can metastasize to the pleura, as these can be early pleural metastases.

Radiologists should be aware of typical features of intrapulmonary lymph nodes as well as red flags to reduce unnecessary follow-up imaging and avoid missing any lung cancers.