A patient with stage IV non-small cell lung cancer of the left lower lobe was admitted with extensive peritoneal metastasis and liver metastasis. CT scan of the lung showed a large tumor in the left lung base with diffuse extension to the right lung. When queried, the provider documented that the tumor had started in the left lung and metastasized to the right lung. Is the presence of cancer in more than one lobe of the lung coded as metastasis or primary cancer of both lungs? What are the correct diagnosis code assignments?
Occasionally more than one primary cancer can occur in the same organ system, and these are called synchronous primary cancers. This can occur in the lungs where the target organ, in this case the respiratory epithelium, is attacked/altered by the inciting agent (e.g., tobacco smoke). However, the physician must make that designation as to whether one of the tumors represents a second primary or a metastasis.
Since the provider has clearly documented that the primary malignancy of the left lung had extended to the right lung, assign code 162.5, Malignant neoplasm lower lobe, bronchus or lung, as the principal diagnosis and code 197.0, Secondary malignant neoplasm of respiratory and digestive systems, Lung, as a secondary diagnosis. In addition, assign codes 197.6, Secondary malignant neoplasm of retroperitoneum, and peritoneum, and 197.7, Secondary malignant neoplasm of liver, specified as secondary.