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Etymology

  • Derived from “lymphadenopathy,” which refers to the enlargement of lymph nodes (lymph glands), and “chest,” indicating the thoracic region.

AKA and abbreviation

  • Mediastinal lymphadenopathy (MLA).

What is it?

  • Lymphadenopathy in the chest refers to the abnormal enlargement of lymph nodes within the thoracic cavity, particularly in the mediastinum or hilar regions.
  • It is a radiologic finding that may indicate infectious, inflammatory, or neoplastic processes affecting the lymphatic system.

Characterized by

  • Normal lymph nodes:
    • Small, oval, or bean-shaped with smooth margins.
    • Typically soft and compressible; do not obstruct adjacent structures unless significantly enlarged (>2 cm).
  • Lymphoma nodes:
    • Soft, mobile, and non-adherent; generally do not obstruct adjacent structures unless significantly enlarged.
    • May coalesce to form large, bulky mediastinal masses.
  • Carcinomatous nodes:
    • Firm to hard and often adherent to surrounding tissues.
    • Tend to obstruct airways or vessels early due to infiltrative growth, even when relatively small (<2 cm).
  • Necrotic nodes:
    • Central necrosis often seen in infectious (e.g., tuberculosis) or malignant nodes.
    • Appears as low-density areas on CT with possible rim enhancement.
  • Calcified nodes:
    • Can exhibit varying patterns of calcification depending on the underlying cause:
      • Central rounded calcifications: Common in healed granulomatous infections like tuberculosis or histoplasmosis.
      • Eccentric calcifications: Seen in metastatic disease or post-radiation therapy.
      • Eggshell calcifications: Peripheral calcifications, characteristic of silicosis or sarcoidosis.
      • Lobulated calcifications: Found in rare conditions like amyloidosis or Castleman disease.
      • Psammommatous calcifications: Lamellated, round calcifications characteristic of metastases from papillary thyroid carcinoma or mucinous adenocarcinomas.
  • Low-density nodes:
    • Caused by necrosis (e.g., tuberculosis, lymphoma, or metastatic disease), cystic changes, or liquefactive processes.
    • Appear hypodense on CT and may indicate aggressive or inflammatory pathology.

Anatomical Context

  • Thoracic lymphadenopathy commonly involves the following regions:
    • Mediastinal nodes: Paratracheal, subcarinal, para-aortic, and prevascular nodes.
    • Hilar nodes: Found at the lung hila, associated with the pulmonary arteries and bronchi.
    • Intrapulmonary nodes: Within the lung parenchyma, usually near the bronchi or pulmonary arteries.

Caused by

Most common cause: Reactive lymphadenopathy secondary to infection.

Other causes include:

  • Infections:
    • Tuberculosis, fungal infections (e.g., histoplasmosis), bacterial pneumonia.
    • Viral infections (e.g., Epstein-Barr virus, cytomegalovirus).
  • Inflammatory/Immune:
    • Sarcoidosis (non-caseating granulomas).
    • Rheumatoid arthritis or systemic lupus erythematosus (SLE).
  • Neoplasm:
    • Primary: Lymphoma (Hodgkin’s or non-Hodgkin’s).
    • Secondary: Metastatic disease from lung, breast, thyroid (papillary carcinoma), or mucinous cancers.
  • Circulatory:
    • Congestive heart failure (CHF): Reactive lymphadenopathy caused by venous and lymphatic congestion; these nodes reduce in size with successful CHF treatment.
  • Other:
    • Lymphangitic carcinomatosis.
    • Chronic granulomatous disease or silicosis.

Resulting in

  • Soft nodes (lymphoma): Compression of adjacent structures only when significantly enlarged.
  • Hard nodes (carcinoma): Early obstruction of bronchi, vessels, or esophagus due to infiltrative growth.

Structural changes

  • Benign processes: Reactive or mildly enlarged nodes with preserved architecture.
  • Malignant processes: Irregular, necrotic, or matted lymph nodes with loss of normal architecture.
  • Calcifications: Present in benign granulomatous lesions or certain metastatic conditions.

Pathophysiology

  • Lymphadenopathy occurs due to immune response, tumor infiltration, or infectious organisms within lymphatic tissue.
  • Chronic conditions can lead to fibrosis or calcification of lymph nodes.

Pathology

  • Benign lymphadenopathy: Reactive hyperplasia due to infection or inflammation.
  • Malignant lymphadenopathy: Lymphoma, metastatic cancer, or lymphatic spread of neoplasms.

Diagnosis

  • Clinical correlation: Symptoms depend on the underlying cause (e.g., fever, weight loss, cough, hemoptysis).
  • Imaging:
    • CXR: May show widened mediastinum or discrete nodal enlargement.
    • CT or PET-CT: Crucial for size, morphology, and metabolic activity.
    • Biopsy: Needed for definitive diagnosis, especially in malignancy or granulomatous disease.

Clinical

  • Symptoms: Asymptomatic in mild cases; severe cases may present with cough, dyspnea, chest pain, or systemic symptoms like fever and night sweats.
  • Signs: Palpable cervical or supraclavicular lymph nodes may accompany thoracic lymphadenopathy.

Radiology Detail

CXR:

  • Findings: Widened mediastinum, hilar prominence, or mass-like opacities.
  • Associated Findings: Pleural effusion or lung consolidation.

CT:

  • Parts: Mediastinal, hilar, and intrapulmonary lymph nodes.
  • Size: Abnormal if >10 mm (general nodes), >12 mm (subcarinal).
  • Shape: Rounded, lobulated, or irregular.
  • Position: Central in mediastinum or peripherally at lung hila.
  • Character:
    • Calcifications:
      • Central, eccentric, eggshell, lobulated, or psammommatous patterns.
      • Psammommatous calcifications suggest papillary thyroid carcinoma or mucinous adenocarcinoma.
    • Low-density nodes: Seen in necrosis, cystic degeneration, or liquefactive processes (e.g., tuberculosis, lymphoma, or metastatic disease).
    • Soft nodes (lymphoma): Compress only when significantly enlarged.
    • Hard nodes (carcinoma): Early obstruction due to invasive growth.
  • Associated Findings: Adjacent lung opacities, vascular invasion, or effusion.

Other relevant Imaging Modalities:

  • MRI: Rarely used but can provide detailed soft-tissue contrast.
  • PET-CT: Detects metabolic activity in malignant or granulomatous lymphadenopathy.
  • Ultrasound (EUS/EBUS): Useful for guided biopsy.

Pulmonary function tests (PFTs)

  • May be normal unless enlarged lymph nodes obstruct airways or compress the lung parenchyma.

Recommendations

  • Imaging follow-up for reactive lymphadenopathy.
  • Biopsy in cases of persistent, necrotic, or metabolically active nodes to rule out malignancy or granulomatous diseases.
  • Treat underlying causes (e.g., infections, malignancy, or autoimmune conditions).

Key Points and Pearls

  • Lymphadenopathy in the chest is commonly due to reactive or infectious processes but requires careful evaluation for malignancy or granulomatous diseases.
  • Short-axis size >10 mm on CT is the general criterion for lymphadenopathy, with specific exceptions for subcarinal and hilar nodes.
  • PET-CT is valuable for assessing metabolic activity and differentiating benign from malignant causes.
  • Patterns of calcification (e.g., eggshell, eccentric, psammommatous, or central) provide diagnostic clues to specific diseases.
  • Soft nodes (lymphoma) compress adjacent structures only when significantly enlarged, whereas hard nodes (carcinoma) infiltrate and obstruct early.