Question: When would you use Z51.12? Is it appropriate to use this code for patients receiving immunotherapy for conditions such as hypogammaglobulinemia, common variable immunodeficiency, or sarcoidosis? AAPC Forum Participant Answer: You would use Z51.12 (Encounter for antineoplastic immunotherapy) to document therapy intended for strengthening the patient’s immune system to fight cancer. However, the conditions you mention are conditions of the immune system, not cancers. Since there is no specific ICD-10-CM code for therapeutic immunotherapy, therapy for these diagnoses would be coded using the appropriate drug therapy code such as Z79.899 (Other long term (current) drug therapy) says Arlene Baril, MHA, RHIA, CHC, Director at Pinnacle Enterprise Risk Consulting Services LLC, Dallas. And remember: You would only use Z51.12 for patients receiving therapies like monoclonal antibodies and cancer vaccines to treat cancers of the prostate, lung, bladder, breast, colon, and kidneys along with cancers such as leukemia, lymphoma, multiple myeloma, and melanoma. For your patients receiving chemotherapy, you should use Z51.11 (Encounter for antineoplastic chemotherapy).