Mediastinal Lymph Nodes Borderline Size on Radiology Reports: What It Means

ByA. Mendelson, MD
Please read the disclaimer

A radiology report of the chest can mention “mediastinal lymph nodes of borderline size.”  The mediastinum is the central part of the chest, located between the lungs, that contains the heart, major blood vessels, esophagus, trachea, and lymph nodes. Lymph nodes in this area are part of the immune system and can become enlarged for many reasons. The term “borderline size” means the lymph nodes are at the upper end of what is considered normal but not clearly abnormal.

What Are Mediastinal Lymph Nodes?

Mediastinal lymph nodes are small, bean-shaped glands that filter lymph fluid and help the body fight infections and diseases. On imaging studies like CT scans or PET/CT, radiologists carefully evaluate these nodes.

Normally, lymph nodes in the chest are small—typically less than 10 millimeters (mm) in short-axis diameter. However, size is not the only factor. Radiologists also look at shape, distribution, and any changes over time.

What Does “Borderline Size” Mean?

The phrase “borderline size” usually refers to lymph nodes that are slightly larger than normal but not large enough to be clearly abnormal. For example:

  • Normal range: less than 10 mm in short axis

  • Borderline range: around 10–14 mm in short axis

  • Abnormal enlargement: greater than 15 mm in short axis

When radiologists describe nodes as borderline, they are signaling that the size alone is not enough to diagnose disease. Additional context—such as the patient’s history, other findings on imaging, and lab results—matters greatly.

Common Causes of Borderline Lymph Node Enlargement

Borderline-sized mediastinal lymph nodes are relatively common. Some possible reasons include:

1. Benign Reactive Changes

  • The immune system reacts to infections or inflammation, causing temporary node enlargement.

  • Conditions like recent respiratory infections, pneumonia, or bronchitis may explain mild enlargement.

2. Chronic Lung Conditions

  • People with chronic obstructive pulmonary disease (COPD) or interstitial lung disease may show borderline lymph nodes due to ongoing inflammation.

3. Sarcoidosis or Autoimmune Disorders

  • Inflammatory conditions like sarcoidosis or rheumatoid arthritis can cause mediastinal lymph nodes to be slightly larger than usual.

5. Early or Low-Grade Malignancy

  • In some cases, borderline nodes may represent early involvement from lung cancer, lymphoma, or metastatic disease.

  • This is why careful follow-up imaging or additional tests may be suggested.

How Radiologists Evaluate Borderline Nodes

When describing lymph nodes, radiologists do more than measure size. They also look for:

  • Shape: Normal nodes are oval. Rounded nodes may raise suspicion.

  • Margins: Smooth edges are more reassuring, while irregular borders can be concerning.

  • Internal appearance: Calcification or fatty centers often suggest a benign process.

  • Comparison with prior scans: Stable size over time is usually not worrisome.

If borderline nodes are found, radiologists often recommend clinical workup, a PET CT scan and possible follow-up CT scan in 3–6 months to check for changes.

Role of PET/CT and Biopsy

Sometimes, CT imaging alone cannot clarify whether a borderline node is benign or suspicious. In these cases:

  • PET/CT can check for abnormal metabolic activity, though false positives and negatives can occur.

  • Endobronchial ultrasound-guided biopsy (EBUS) or mediastinoscopy may be used to sample the node for a more definitive answer.

What Patients Should Know

Hearing “borderline lymph node enlargement” on a radiology report does not mean cancer. In fact, most borderline nodes are benign or reactive. Still, radiologists flag them because:

  • They want referring doctors to be aware of the finding.

  • Further imaging follow-up may be appropriate.

  • Rarely, it can be an early sign of something more serious.

When to Ask Your Doctor About Next Steps

If your imaging report mentions mediastinal lymph nodes of borderline size, it’s reasonable to ask:

  • Do I need a follow-up CT, and when?

  • Do I have any risk factors (smoking, prior cancers, chronic lung disease) that make this more significant?

  • Could blood tests or additional imaging studies provide clarity?

  • At what point would a biopsy be considered?

Bottom Line

“Mediastinal lymph nodes of borderline size” means that your lymph nodes are slightly larger than average but not clearly abnormal.  In most cases, this is due to benign or reactive causes such as infection or inflammation. Radiologists note these findings carefully to guide safe follow-up.

For many people, borderline nodes simply need monitoring over time rather than immediate invasive testing. Staying in close communication with your doctor and following recommended imaging schedules is the best approach.

References

https://radiopaedia.org/articles/mediastinal-lymph-node-enlargement

https://www.ncbi.nlm.nih.gov/books/NBK532863/

https://pmc.ncbi.nlm.nih.gov/articles/PMC2821588/

Disclaimer: The content of this website is provided for general informational purposes only and is not intended as, nor should it be considered a substitute for, professional medical advice. Do not use the information on this website for diagnosing or treating any medical or health condition. If you have or suspect you have a medical problem, promptly contact your professional healthcare provider.

Similar Posts