Secondary malignant neoplasm of left lung

This code signifies the presence of a malignant tumor in the left lung that originated from a primary cancer site elsewhere in the body and subsequently spread to the lung. It indicates metastatic disease affecting the left lung, rather than a primary lung cancer.

Use this code when documentation clearly states metastatic cancer to the left lung, with the primary site either known or unknown. This applies when the left lung is identified as a secondary site of malignancy, often following imaging studies (e.g., CT scan, PET scan) and/or biopsy confirmation.

• Always code the primary malignancy first, if known, followed by this code for the secondary site.
• Distinguish carefully between primary lung cancer (C34.-) and secondary lung cancer; documentation must specify "metastatic to" or "secondary malignant neoplasm of."
• If laterality is not specified in the documentation, use the unspecified lung code (C78.00).