Question: Documentation indicates malignant pleural effusion in a patient with malignant cancer of the main bronchus. What codes would you bill in this case? Florida Subscriber Answer: You should wait for the final diagnosis from cytology to confirm malignant effusion. But once confirmed, you should bill 511.81 (Malignant pleural effusion) to represent the malignant effusion. A note with 511.81 tells you to "code first malignant neoplasm, if known," such as 162.2 (Malignant neoplasm of trachea, bronchus and lung; main bronchus). Keep in mind: