2026 ICD-10-CM Diagnosis Code Z85.821Personal history of Merkel cell carcinoma

ICD-10-CM Codes›Z00–Z99›Z77-Z99›Z85

ICD-10-CM Z85.821
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

Z85.821 is a billable ICD-10-CM diagnosis code for personal history of Merkel cell carcinoma. 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. Coders also document this condition as history of merkel cell carcinoma. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Personal history of malignant neoplasm.

Code Identity

ICD-10-CM Code
Z85.821
Billable Status
Yes — Valid for Submission
Code Describes
Personal history of Merkel cell carcinoma
Short Description
Personal history of Merkel cell carcinoma
Same as the full description in the CMS dataset.
Parent Code
Z85.82
Personal history of malignant neoplasm of skin

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 CodeZ85.821Personal history of Merkel cell carcinoma

Code EditsBilling

Medicare Code Editor checks that affect claim validity for Z85.821.

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

Z85.821 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.

  • History of merkel cell carcinoma

Tabular List NotesGuidance

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

Inclusion Terms

  • Conditions classifiable to C4A

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)
          • Merkel cell
    • History
      • personal (of)
        • malignant neoplasm (of)
          • skin NEC
            • Merkel cell
    • History
      • personal (of)
        • Merkel cell carcinoma (skin)

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

Skin Cancer

Skin cancer is the most common form of cancer in the United States. The two most common types are basal cell cancer and squamous cell cancer. They usually form on the head, face, neck, hands, and arms. Another type of skin cancer, melanoma, is more dangerous but less common.

Read the full article at MedlinePlus

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

Convert Z85.821 to ICD-9-CMHistory

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

ICD-9-CM
V10.91 Hx malig neuroendo tumor
Approximate The match is approximate rather than exact.

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 Z85.821Overview

Is Z85.821 (Personal history of malignant neoplasm of skin) a billable code?

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

What MS-DRG does Z85.821 group to?

On inpatient claims, personal history of Merkel cell carcinoma 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 Z85.821 be a principal diagnosis?

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

Is Z85.821 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 Merkel cell carcinoma on inpatient claims.

What is the ICD-9 equivalent of Z85.821?

Under the General Equivalence Mappings, personal history of Merkel cell carcinoma converts to ICD-9-CM V10.91 (hx malig neuroendo tumor). The mapping is approximate, so confirm the match fits the documentation.