2026 ICD-10-CM Diagnosis Code Z85.850Personal history of malignant neoplasm of thyroid

ICD-10-CM Codes›Z00–Z99›Z77-Z99›Z85

ICD-10-CM Z85.850
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

Z85.850 is a billable ICD-10-CM diagnosis code for personal history of malignant neoplasm of thyroid. 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, 843 through 845. 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 Personal history of malignant neoplasm.

Code Identity

ICD-10-CM Code
Z85.850
Billable Status
Yes — Valid for Submission
Code Describes
Personal history of malignant neoplasm of thyroid
Short Description
Personal history of malignant neoplasm of thyroid
Same as the full description in the CMS dataset.
Parent Code
Z85.85
Personal history of malignant neoplasm of endocrine glands

Code Classification

ChapterZ00–Z99Factors influencing health status and contact with health services
SectionZ77-Z99Persons with potential health hazards related to family and personal history and certain conditions influencing health status
CategoryZ85Personal history of malignant neoplasm
This CodeZ85.850Personal history of malignant neoplasm of thyroid

Code EditsBilling

Medicare Code Editor checks that affect claim validity for Z85.850.

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

Z85.850 is exempt from POA reporting on inpatient claims to general acute care hospitals. Review other POA exempt codes.

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • H/O: thyroid disorder
  • History of follicular adenocarcinoma of thyroid
  • History of malignant neoplasm of endocrine gland
  • History of malignant neoplasm of neck
  • History of malignant neoplasm of thyroid
  • History of medullary carcinoma of thyroid
  • History of papillary adenocarcinoma of thyroid

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.

    • History
      • personal (of)
        • malignant neoplasm (of)
          • thyroid

Clinical ClassificationClinical

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

CCSR FAC027
Personal history of malignant neoplasm
Default principal diagnosis: inpatient No · outpatient Yes

Patient EducationClinical

Thyroid Cancer

Thyroid cancer is a cancer that starts in the tissues of the thyroid. Your thyroid is a small, butterfly-shaped gland in the front of your neck. It makes hormones that control the way the body uses energy. These hormones affect nearly every organ in your body and control many of your body's most important functions.

The full article covers:

  • What is thyroid cancer?
  • What are the different types of thyroid cancer?
  • Who is more likely to develop thyroid cancer?
  • What are the symptoms of thyroid cancer?
  • How is thyroid cancer diagnosed?
  • What are the treatments for thyroid cancer?

Read the full article at MedlinePlus

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

Convert Z85.850 to ICD-9-CMHistory

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

ICD-9-CM
V10.87 Hx of thyroid malignancy
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 Z85.850Overview

Is Z85.850 (Personal history of malignant neoplasm of endocrine glands) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report personal history of malignant neoplasm of thyroid on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does Z85.850 group to?

On inpatient claims, personal history of malignant neoplasm of thyroid maps to MS-DRG 826, 827, 828, 829, 830, 843, 844, 845, with relative weights from 0.8516 to 4.6778 depending on complications. Higher weights mean higher Medicare reimbursement.

Can Z85.850 be a principal diagnosis?

No. The Medicare Code Editor rejects this code as a principal diagnosis because personal history of malignant neoplasm of thyroid describes a circumstance that influences health status rather than a current illness. Report it as a secondary diagnosis.

Is Z85.850 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 personal history of malignant neoplasm of thyroid on inpatient claims.

What is the ICD-9 equivalent of Z85.850?

Under the General Equivalence Mappings, personal history of malignant neoplasm of thyroid converts to ICD-9-CM V10.87 (hx of thyroid malignancy). The mapping is a direct match.