Admission/Encounter for treatment of primary site

If the malignancy is chiefly responsible for occasioning the patient admission/encounter and treatment is directed at the primary site, designate the primary malignancy as the principal/first-listed diagnosis. The only exception to this guideline is if the administration of chemotherapy, immunotherapy or external beam radiation therapy is chiefly responsible for occasioning the admission/encounter.

In that case, assign the appropriate Z51.-- code as the first-listed or principal diagnosis, and the underlying diagnosis or problem for which the service is being performed as a secondary diagnosis.