Why can enlarged lymph nodes in the neck be an early sign of lung cancer?

Enlarged lymph nodes in the neck can be an early sign of lung cancer because these nodes serve as drainage sites for the affected area.1

The lymphatic system functions as a filter for the body, and lymph nodes are vulnerable to cancer because they can trap and concentrate cancerous cells as they spread through metastasis. In the case of lung disease, the thoracic duct—the body's principal channel for lymph—runs upward to the base of the neck. Consequently, the swelling of small lymph nodes located above the collarbone in the neck can indicate underlying intrathoracic disease, making such enlargement a clinical sign that warrants medical investigation.12