2026 ICD-10-CM Diagnosis Code Z51.12Encounter for antineoplastic immunotherapy

ICD-10-CM Codes›Z00–Z99›Z40-Z53›Z51

ICD-10-CM Z51.12
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

Z51.12 is a billable ICD-10-CM diagnosis code for encounter for antineoplastic immunotherapy. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 826 through 830, 837 through 839, 846 through 848. The code is exempt from POA reporting. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Encounter for antineoplastic therapies.

Code Identity

ICD-10-CM Code
Z51.12
Billable Status
Yes — Valid for Submission
Code Describes
Encounter for antineoplastic immunotherapy
Short Description
Encounter for antineoplastic immunotherapy
Same as the full description in the CMS dataset.
Parent Code
Z51.1
Encounter for antineoplastic chemotherapy and immunotherapy

Code Classification

ChapterZ00–Z99Factors influencing health status and contact with health services
SectionZ40-Z53Encounters for other specific health care
CategoryZ51Encounter for other aftercare and medical care
This CodeZ51.12Encounter for antineoplastic immunotherapy

Present on Admission (POA)Billing

Z51.12 is exempt from POA reporting on inpatient claims to general acute care hospitals. Review other POA exempt codes.

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

External Cause of Injuries IndexGuidance

References for this code in the External Cause of Injuries Index.

    • Encounter(with health service) (for)
      • immunotherapy for neoplasm
    • Immunotherapy(encounter for)
      • antineoplastic

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR FAC006
Encounter for antineoplastic therapies
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Cancer Immunotherapy

Immunotherapy is a cancer treatment that helps your immune system fight cancer. It is a type of biological therapy. Biological therapy uses substances made from living organisms or versions of these substances made in a lab. Immunotherapy isn't used for all cancers, and the response to treatment varies.

The full article covers:

  • What is immunotherapy?
  • When is immunotherapy used for cancer treatment?
  • How does immunotherapy work against cancer?
  • How is immunotherapy given?
  • What are the side effects of immunotherapy?

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert Z51.12 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
V58.12 Immunotherapy encounter
Exact Match The mapping is direct, with no qualifiers.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About Z51.12Overview

Is Z51.12 (Encounter for antineoplastic chemotherapy and immunotherapy) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report encounter for antineoplastic immunotherapy on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does Z51.12 group to?

When encounter for antineoplastic immunotherapy is the principal diagnosis on an inpatient stay, it groups to MS-DRG 826, 827, 828, 829, 830, 837, 838, 839, 846, 847, 848, with relative weights from 0.8494 to 4.8043 depending on complications. Higher weights mean higher Medicare reimbursement.

Is Z51.12 exempt from POA reporting?

Yes. CMS lists this code among those exempt from present on admission reporting, so hospitals do not assign a POA indicator for encounter for antineoplastic immunotherapy on inpatient claims.

What is the ICD-9 equivalent of Z51.12?

Under the General Equivalence Mappings, encounter for antineoplastic immunotherapy converts to ICD-9-CM V58.12 (immunotherapy encounter). The mapping is a direct match.