From the Guidelines
The subcarinal lymph node is located in the chest, specifically in the mediastinum, and a node measuring 1.3 cm that shows stability in size over time is at the upper limit of normal size, according to the most recent guidelines 1. The location of the subcarinal node is directly beneath the carina, which is the point where the trachea divides into the right and left main bronchi. Generally, mediastinal lymph nodes, including subcarinal nodes, are considered normal when they measure less than 1 cm in short-axis diameter, with some experts accepting up to 1.5 cm as the upper limit for subcarinal nodes specifically, as stated in the revised response criteria for malignant lymphoma 1. However, the most recent study from 2018 1 suggests that a short-axis size threshold of 15 mm guides the decision process for managing incidental mediastinal lymph nodes. The stability in size is a reassuring finding, as it suggests that there has not been progression or growth that might indicate a pathological process such as infection, inflammation, or malignancy. Subcarinal nodes can enlarge due to various conditions including infections, sarcoidosis, lung cancer, lymphoma, or metastatic disease from other primary cancers. When evaluating lymph nodes, both size and stability over time are important factors in determining clinical significance, and other features of lymph nodes, such as shape, the presence of a fatty hilum, and calcification, are also important to consider, as noted in the study by Evison et al, referenced in 1. In this case, since the subcarinal node measures 1.3 cm and shows stability in size, it is likely to be at the upper limit of normal size, and further evaluation or follow-up may be necessary to determine its clinical significance, as recommended in the guidelines for managing incidental findings on thoracic CT 1. Some key points to consider in the evaluation of lymph nodes include:
- Size: a short-axis size threshold of 15 mm guides the decision process
- Texture or density: if enlarged, the texture or density of the node should be evaluated
- Fluorine-18-2-fluoro-2-deoxy-D-glucose (FDG) activity: if on PET/CT examination, the FDG activity of the node should be evaluated
- Clinical history: can be a deciding factor in overall management
- Pulmonary findings: are important in determining management of lymph nodes.
From the Research
Location of Subcarinal Node
- The subcarinal node is located in the mediastinum, which is the central part of the chest cavity containing the heart, trachea, esophagus, and other structures.
- Specifically, it is situated below the carina, which is the point where the trachea divides into the right and left bronchi.
Normal Size Range of Subcarinal Node
- According to the study 2, the size threshold for abnormal nodal enlargement with CT imaging is 11 mm in short axis.
- The study 3 suggests that subcarinal nodes less than 10 mm in short-axis diameter by CT are unlikely to be malignant, with only 1% of patients having a positive result.
- The size of the subcarinal node in the question is 1.3 cm, which is approximately 13 mm, indicating that it may be considered enlarged.
Stability in Size
- The question mentions that the subcarinal node is showing stability in size, which may indicate that it is not rapidly growing or changing.
- However, the studies do not provide specific information on the significance of stability in size, and further evaluation may be necessary to determine the nature of the node.