ICD-10 Code C78.0 – Secondary malignant neoplasm of lung (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code C78.0 – Secondary malignant neoplasm of lung
What it is
C78.0 identifies metastatic cancer in the lung, meaning a primary malignancy from another site has spread to pulmonary tissue. Use it when the lung involvement is documented as secondary, not primary.
Clinical signs
Clinical features vary; refer to documentation. Commonly, records note pulmonary nodules, cough, shortness of breath, hemoptysis, or imaging evidence consistent with metastatic disease.
When to use this code
Use C78.0 when the clinician documents secondary malignant neoplasm of the lung, lung metastases, or metastatic deposits in the lung from another primary site. It is appropriate when imaging, pathology, or oncology notes clearly support secondary involvement. If the record only says “lung cancer,” check whether the primary site is specified.
Do not use for
Do not use this code for primary lung cancer or for nonspecific pulmonary nodules without a documented malignant cause. Check documentation if the chart does not clearly state metastatic disease.
Coding tip
Always code the primary cancer first when it is known, and use C78.0 only for the metastatic lung site.