2026 ICD-10-CM Diagnosis Code Z17.421Hormone receptor negative with human epidermal growth factor receptor 2 negative status

ICD-10-CM Codes›Z00–Z99›Z17›Z17

ICD-10-CM Z17.421
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

Z17.421 is a billable ICD-10-CM diagnosis code for hormone receptor negative with human epidermal growth factor receptor 2 negative status. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026). The code is not accepted as a principal diagnosis by the Medicare Code Editor and exempt from POA reporting. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Genetic susceptibility to disease.

Code Identity

ICD-10-CM Code
Z17.421
Billable Status
Yes — Valid for Submission
Code Describes
Hormone receptor negative with human epidermal growth factor receptor 2 negative status
Short Description
Hormone recept neg w hmn epdrml grth fctr recept 2 neg stat
Parent Code
Z17.42
Hormone receptor negative

Code Classification

ChapterZ00–Z99Factors influencing health status and contact with health services
SectionZ17Estrogen, and other hormones and factors receptor status
CategoryZ17Estrogen, and other hormones and factors receptor status
This CodeZ17.421Hormone receptor negative with human epidermal growth factor receptor 2 negative status

Code EditsBilling

Medicare Code Editor checks that affect claim validity for Z17.421.

Unacceptable principal diagnosis
There are selected codes that describe a circumstance which influences an individual's health status but not a current illness or injury, or codes that are not specific manifestations but may be due to an underlying cause. These codes are considered unacceptable as a principal diagnosis.

Present on Admission (POA)Billing

Z17.421 is exempt from POA reporting on inpatient claims to general acute care hospitals. Review other POA exempt codes.

Tabular List NotesGuidance

Coding notes and annotation back-references applicable to this code.

Inclusion Terms

  • HR- with HER2-
  • TNBC
  • Triple negative breast cancer

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.

    • Status(post)
      • combined receptor
        • negative
          • hormone receptor negative with human epidermal growth factor receptor 2 negative
    • Triple
      • negative breast cancer (TNBC)

Clinical ClassificationClinical

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

CCSR FAC029
Genetic susceptibility to disease
Default principal diagnosis: inpatient No · outpatient No

Clinical InformationClinical

  • Advanced Hormone Receptor-Negative Breast Carcinoma|Advanced Hormone Receptor Negative Breast Carcinoma

    hormone receptor-negative breast carcinoma that has spread extensively to other anatomic sites or is no longer responding to treatment.

  • Hormone Receptor Negative

    a finding indicating that the tumor cells in a tissue sample are negative for hormone receptors.

  • Hormone Receptor-Negative Breast Carcinoma|ER and PR Negative Breast Carcinoma|Estrogen Receptor and Progesterone Receptor Negative Breast Carcinoma|Hormone Receptor Negative Breast Adenocarcinoma|Hormone Receptor Negative Breast Carcinoma|Hormone Receptor Negative Breast Carcinoma

    breast adenocarcinoma that is negative for hormone receptors.

  • Metastatic Hormone Receptor-Negative Breast Carcinoma|Metastatic Hormone Receptor Negative Breast Carcinoma

    hormone receptor-negative breast carcinoma that has spread from its original site of growth to another anatomic site.

  • Recurrent Hormone Receptor-Negative Breast Carcinoma|Recurrent Hormone Receptor Negative Breast Adenocarcinoma|Recurrent Hormone Receptor Negative Breast Carcinoma|Recurrent Hormone Receptor-Negative Breast Adenocarcinoma

    the reemergence of hormone receptor-negative breast carcinoma after a period of remission.

  • Refractory Hormone Receptor-Negative Breast Carcinoma|Refractory Hormone Receptor Negative Breast Adenocarcinoma|Refractory Hormone Receptor Negative Breast Carcinoma|Refractory Hormone Receptor-Negative Breast Adenocarcinoma

    hormone receptor-negative breast carcinoma that is resistant to treatment.

  • Unresectable Hormone Receptor-Negative Breast Carcinoma|Unresectable Hormone Receptor Negative Breast Carcinoma

    hormone receptor-negative breast carcinoma that is not amenable to surgical resection.

  • Advanced Hormone Receptor-Negative Breast Carcinoma|Advanced Hormone Receptor Negative Breast Carcinoma|Advanced Hormone Receptor-Negative Breast Adenocarcinoma

    a hormone receptor-negative breast adenocarcinoma that has spread extensively to other anatomic sites or is no longer responding to treatment.

  • Metastatic Hormone Receptor-Negative Breast Carcinoma|Metastatic Hormone Receptor Negative Breast Carcinoma|Metastatic Hormone Receptor-Negative Breast Adenocarcinoma

    hormone receptor-negative breast adenocarcinoma that has spread from its original site of growth to another anatomic site.

  • Recurrent Hormone Receptor-Negative Breast Carcinoma|Recurrent Hormone Receptor Negative Breast Adenocarcinoma|Recurrent Hormone Receptor Negative Breast Carcinoma|Recurrent Hormone Receptor-Negative Breast Adenocarcinoma

    the reemergence of hormone receptor-negative breast adenocarcinoma after a period of remission.

  • Refractory Hormone Receptor-Negative Breast Carcinoma|Refractory Hormone Receptor Negative Breast Adenocarcinoma|Refractory Hormone Receptor Negative Breast Carcinoma|Refractory Hormone Receptor-Negative Breast Adenocarcinoma

    hormone receptor-negative breast adenocarcinoma that is resistant to treatment.

  • Unresectable Hormone Receptor-Negative Breast Carcinoma|Unresectable Hormone Receptor Negative Breast Carcinoma|Unresectable Hormone Receptor-Negative Breast Adenocarcinoma

    hormone receptor-negative breast adenocarcinoma that is not amenable to surgical resection.

Code HistoryHistory

FY 2025AddedAdded to the ICD-10-CM code setEffective October 1, 2024.
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About Z17.421Overview

Is Z17.421 (Hormone receptor negative) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report hormone receptor negative with human epidermal growth factor receptor 2 negative status on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

Can Z17.421 be a principal diagnosis?

No. The Medicare Code Editor rejects this code as a principal diagnosis because hormone receptor negative with human epidermal growth factor receptor 2 negative status describes a circumstance that influences health status rather than a current illness. Report it as a secondary diagnosis.

Is Z17.421 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 hormone receptor negative with human epidermal growth factor receptor 2 negative status on inpatient claims.