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Subcarinal lymph nodes

The subcarinal lymph nodes are part of the mediastinal lymph node group, located in the subcarinal space beneath the tracheal carina, between the origins of the left and right main bronchi. They correspond to Station 7 in the IASLC lymph node map used for lung cancer staging.

These nodes are important in the drainage of both lungs, particularly from the lower lobes, and receive lymphatic input from hilar and intrapulmonary nodes. Clinically, subcarinal nodes are central to the staging of lung cancer, lymphoma assessment, sarcoidosis, and tuberculosis. Enlargement of subcarinal nodes is a critical finding in oncology and infectious disease imaging.

Synonyms

  • Station 7 lymph nodes

  • Inferior tracheobronchial nodes

  • Carinal lymph nodes

Function

  • Drain lymph from the lungs (especially lower lobes), bronchi, and mediastinal structures

  • Participate in immune surveillance and filtration of lymph from thoracic organs

  • Serve as key markers in lung cancer staging (N2 involvement)

  • Important in mediastinal disease diagnosis (e.g., TB, sarcoidosis, lymphoma)

MRI Appearance

T1-weighted images:

  • Normal subcarinal nodes: isointense to muscle, slightly hypointense to mediastinal fat

  • Enlarged/pathologic nodes: appear as well-defined intermediate signal masses

T2-weighted images:

  • Normal nodes: intermediate to slightly hyperintense relative to muscle

  • Pathologic nodes (inflammatory or malignant): often more hyperintense

  • Necrotic nodes: heterogeneous high signal with central fluid-like areas

T2 TRUFISP (cardiac/respiratory-gated):

  • Provides clear dynamic contrast between nodes, vessels, and bronchi

  • Enlarged subcarinal nodes appear as rounded intermediate-signal structures in the subcarinal space

  • Useful for detecting mass effect on bronchi or esophagus

STIR (Short Tau Inversion Recovery):

  • Suppresses fat, improving conspicuity of lymph nodes

  • Enlarged nodes appear bright hyperintense against suppressed mediastinal fat

  • Helpful in distinguishing nodes from adjacent vascular structures

T1 Post-Contrast (Gadolinium-enhanced MRI):

  • Normal nodes enhance mildly and homogeneously

  • Pathologic nodes (malignant or inflammatory) show intense, heterogeneous, or rim enhancement

  • Necrotic nodes: peripheral enhancement with non-enhancing center

CT Appearance

Contrast-Enhanced CT (CECT):

  • Normal subcarinal nodes: usually <1 cm short-axis diameter and difficult to distinguish from surrounding fat

  • Enlarged nodes: seen as well-defined soft tissue masses beneath the carina

  • Malignant nodes: may show irregular borders, central necrosis, or conglomeration

  • Inflammatory nodes: often homogeneously enhancing

  • Essential for lung cancer staging, lymphoma evaluation, and infection workup

MRI image

Subcarinal Lymph nodes anatomy mri coronal image -img-00000-00000

CT image

Subcarinal Lymph nodes anatomy CT coronal image -img-00000-00000