What is the cause of mediastinal adenopathy (enlarged lymph nodes in the mediastinum)?

From the Guidelines

Mediastinal adenopathy should be evaluated with a CT scan with contrast as the initial imaging modality, followed by tissue sampling if necessary, to determine the underlying cause and guide treatment. This condition refers to enlarged lymph nodes in the mediastinum, the central compartment of the thoracic cavity containing the heart, esophagus, trachea, and other structures. The cause of mediastinal adenopathy can vary, including infections (tuberculosis, histoplasmosis), malignancies (lymphoma, lung cancer, metastatic disease), inflammatory disorders (sarcoidosis), or reactive changes 1.

Diagnosis and Evaluation

Diagnosis typically involves chest imaging, with a CT scan with contrast preferred over X-ray for better visualization 1. The CT scan should be evaluated for the size, texture, and location of the lymph nodes, as well as any associated findings such as pulmonary lesions or pleural effusions. If the CT scan is inconclusive, further evaluation with positron emission tomography (PET) or magnetic resonance imaging (MRI) may be necessary 1.

Tissue Sampling

Tissue sampling may be necessary to determine the underlying cause of mediastinal adenopathy. This can be done through various methods, including:

• Mediastinoscopy: a surgical procedure that involves inserting a scope through an incision in the neck to visualize the mediastinum and obtain tissue samples 1.
• Endobronchial ultrasound-guided biopsy: a minimally invasive procedure that uses ultrasound to guide a biopsy needle into the lymph nodes 1.
• CT-guided needle biopsy: a minimally invasive procedure that uses CT guidance to insert a biopsy needle into the lymph nodes 1.

Treatment and Prognosis

Treatment depends entirely on the underlying cause of mediastinal adenopathy. Antibiotics may be used to treat bacterial infections, antifungals for fungal infections, chemotherapy and/or radiation for malignancies, or corticosteroids for inflammatory conditions 1. The prognosis varies significantly based on the cause, with some infectious or inflammatory causes being completely treatable while malignant causes may have more guarded outcomes. Any unexplained mediastinal adenopathy should prompt referral to a pulmonologist or thoracic surgeon for proper evaluation and management 1.

Key Considerations

Some key considerations in the evaluation and management of mediastinal adenopathy include:

• The size and location of the lymph nodes, as well as any associated findings such as pulmonary lesions or pleural effusions 1.
• The presence of symptoms such as chest pain, cough, or shortness of breath, which can indicate a more serious underlying condition 1.
• The patient's medical history, including any previous cancers or infections, which can inform the diagnosis and treatment plan 1.

From the Research

Causes of Mediastinal Adenopathy

• Malignancy (lung cancer, lymphoma, and extrathoracic cancer) and granulomatous conditions (sarcoidosis and tuberculosis) are the most common causes of mediastinal lymphadenopathy 2
• In patients without previous cancer, malignant mediastinal lymphadenopathy originates from the lung in more than 80% of cases 3
• In patients with previous malignancy, recurrence of extrathoracic sites is the major cause of mediastinal lymphadenopathy 3

Diagnosis of Mediastinal Adenopathy

• Thoracic imaging modalities, such as CT scans, are the initial clue to the presence of enlarged mediastinal lymph nodes 2
• Endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA) is a safe and minimally invasive alternative for cytodiagnosis in the mediastinum 3
• EUS-FNA has a high diagnostic yield for the differential diagnosis of tuberculosis and sarcoidosis that have not been diagnosed by conventional methods 4
• Mediastinoscopy is a safe but invasive procedure and provides a tissue diagnosis in most cases of tuberculous mediastinal lymphadenopathy 5

Characteristics of Mediastinal Adenopathy

• The size of lymph nodes on EUS can vary from 0.5 cm to 4.2 cm, with tuberculosis nodes being significantly smaller than those in sarcoidosis 4
• Enhancement characteristics of tuberculous adenopathy can differ from those described previously, with 'ghost-like' ring enhancement being a typical feature 6
• The subcarinal region is the most frequently involved site in mediastinal lymphadenopathy, and multifocal involvement is common 6

Treatment of Mediastinal Adenopathy

• Six months of treatment with rifampicin and isoniazid, supplemented initially by pyrazinamide, is adequate for most adults with tuberculous mediastinal lymphadenopathy 5
• Accurate diagnosis is necessary for optimal management of mediastinal lymphadenopathy, and selecting an appropriate tissue diagnosis modality is crucial 2