ICD-10 Code C77.1 – Secondary and unspecified malignant neoplasm of intrathoracic lymph nodes (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code C77.1 – Secondary and unspecified malignant neoplasm of intrathoracic lymph nodes
What it is
This code identifies metastatic cancer involving lymph nodes inside the chest, including mediastinal or other intrathoracic nodes. Use it when the record shows secondary malignant involvement and the primary site is elsewhere or not specified.
Clinical signs
Findings may include enlarged intrathoracic lymph nodes on imaging, biopsy-proven metastatic disease, or staging documentation confirming nodal spread. Clinical features vary; refer to documentation.
When to use this code
Use C77.1 when the provider documents secondary malignant neoplasm in intrathoracic lymph nodes, such as mediastinal node metastasis from a known primary cancer. It also applies when the record states unspecified malignant involvement of these nodes. Check documentation if the primary site is unclear.
Do not use for
Do not use this code for benign lymph node enlargement, inflammatory disease, or primary malignant tumors of the lymph nodes. If the chart does not confirm metastatic disease, check documentation.
Coding tip
Sequence the primary cancer and any additional metastatic sites according to the record and coding guidelines.