Pathology/Lab Coding Alert

Question: If the pathologist examines a malignant lung wedge biopsy for metastasis to the lung of a cancer that originated in the breast, how should I assign the diagnosis codes?


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Answer: You should list the lung metastasis (197.0, Secondary malignant neoplasm of respiratory and digestive systems; lung) as the primary diagnosis even though it is the secondary condition.

Why: When you direct the procedure toward the secondary site only--in this case, a biopsy of the lung tissue--you should code the secondary neoplasm as the principal diagnosis.

To assign the correct secondary diagnosis code, you'll need to know whether the treating physician has done three things for the primary breast cancer: previously excised or eradicated the primary malignancy, stopped treating the original neoplasm's site, and found no evidence of existing primary malignancy.

If the physician has done all three, you should assign history-of-cancer code V10.3 (Personal history of malignant neoplasm; breast) as the secondary code. But if not, you may list 174.9 (Malignant neoplasm of female breast; breast [female], unspecified) as the secondary diagnosis.