ICD-10 Code C78.01 – Secondary malignant neoplasm of right lung (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code C78.01 – Secondary malignant neoplasm of right lung
What it is
C78.01 identifies metastatic cancer involving the right lung. Use it when a malignancy from another primary site has spread to the right lung, and the record specifically documents the right lung as the secondary site.
Clinical signs
Clinical features vary; refer to documentation. Imaging may show one or more metastatic lesions in the right lung, and pathology or oncology notes may confirm secondary involvement.
When to use this code
Use this code when the provider documents metastatic disease to the right lung from a known primary cancer. It is appropriate for encounters focused on staging, evaluation, or follow-up of the secondary lung site. If the laterality is not stated, check documentation before assigning a unilateral code.
Do not use for
Do not use C78.01 for a primary lung cancer, even if the tumor is in the right lung. Do not use it when the record only says “lung metastases” without right-sided laterality; check documentation.
Coding tip
Capture the primary cancer code first, then assign C78.01 only when the right lung metastasis is clearly documented.