Mediastinal Lymphadenopathy

Mediastinal lymphadenopathy refers to enlarged lymph nodes in the mediastinum, the central part of the chest between the lungs. This condition is often discovered on imaging studies such as chest X-rays or CT scans. Mediastinal lymphadenopathy can be associated with infections, inflammation, or cancer. Understanding what this finding means can help patients and their doctors decide on the next steps.

How Radiologists Detect Enlarged Mediastinal Lymph Nodes

Radiologists identify mediastinal lymphadenopathy primarily through chest X-rays and CT scans.

• Chest X-ray: A basic but limited tool. It may show a widened mediastinum, but it does not provide detailed images of individual lymph nodes.
• CT scan of the chest: The gold standard for assessing mediastinal lymphadenopathy. It provides detailed cross-sectional images, allowing radiologists to measure lymph node size, shape, and distribution.
• PET-CT scan: Sometimes used to evaluate whether the enlarged lymph nodes are metabolically active, which can help differentiate between benign and malignant causes although there is overlap in the appearance.

In general, lymph nodes larger than 1 cm in short-axis diameter on a CT scan are considered abnormal, though clinical context is important.

Common Causes of Mediastinal Lymphadenopathy

1. Infections

Many infections can cause mediastinal lymph node enlargement. Some of the most common include:

• Tuberculosis (TB): Often causes a pattern of enlarged lymph nodes.
• Pneumonia: Bacterial and viral pneumonia can lead to temporary reactive lymph node enlargement.
• Histoplasmosis: A fungal infection commonly found in the Ohio and Mississippi River valleys, which can cause calcified lymph nodes over time.

2. Inflammatory Conditions

• Sarcoidosis: A non-infectious condition where immune cells cluster in the lungs and lymph nodes. CT scans often show a characteristic pattern of symmetrical hilar and mediastinal lymphadenopathy.
• Autoimmune diseases: Conditions like rheumatoid arthritis and lupus can cause lymph node enlargement due to chronic inflammation.

3. Cancer-Related Causes

• Lymphoma: A cancer of the lymphatic system that can cause large, bulky lymph nodes. Radiologists look for clusters of significantly enlarged nodes.
• Lung Cancer: Often spreads to mediastinal lymph nodes. PET-CT scans help determine if the lymph nodes are cancerous.
• Metastatic Disease: Cancers from other organs, such as breast or gastrointestinal tumors, can spread to mediastinal lymph nodes.

Imaging Features That Help Determine the Cause

Radiologists evaluate several characteristics of mediastinal lymphadenopathy to assess the underlying cause:

• Size: Larger nodes (especially over 2 cm) are more concerning for malignancy, but size alone is not diagnostic.
• Distribution: Symmetrical hilar lymphadenopathy is typical of sarcoidosis, while isolated, bulky nodes may suggest lymphoma or cancer.
• Calcifications: Seen in old infections like tuberculosis or histoplasmosis. Calcified lymph nodes are typically benign.
• Necrosis: Nodes with central areas of breakdown (necrosis) can indicate infections like TB or certain cancers.
• Metabolic Activity (on PET-CT scans): High uptake of the radiotracer suggests active disease, whether from cancer or infection.

What Happens Next?

If mediastinal lymphadenopathy is detected, the next steps depend on the suspected cause:

• Follow-up imaging: a repeat CT scan in 3-6 months may be recommended in some cases depending on the clinical context.
• Bronchoscopy with biopsy: A minimally invasive way to sample lymph nodes through the airway.
• Mediastinoscopy: A surgical procedure that allows direct biopsy of mediastinal lymph nodes.
• Blood tests: To check for infections, inflammatory markers, or cancer-related changes.

My Experience as a Radiologist

In my practice, I frequently see mediastinal lymphadenopathy in patients with lung infections, especially those recovering from pneumonia or viral illnesses. Many of these cases resolve on follow-up imaging after treatment. However, when lymph nodes appear unusually large, clustered, or have concerning features like necrosis, further testing is essential to rule out cancer or serious infections.

Conclusion

Mediastinal lymphadenopathy is a common finding on imaging and can have many different causes. While infections and inflammatory conditions are often responsible, cancer must always be considered when lymph nodes appear abnormal. A CT scan provides valuable information, and in some cases, additional tests like PET scans or biopsies are needed. If you see this term in your radiology report, discuss it with your doctor to determine the best course of action.

References

1. https://pubmed.ncbi.nlm.nih.gov/33888038/
2. https://radiopaedia.org/articles/mediastinal-lymph-node-enlargement?lang=us
3. https://www.sciencedirect.com/science/article/pii/S0954611116300178