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ICD-10-CM 2027 diagnosis code

C80.1Malignant (primary) neoplasm, unspecified

✓ Billable / specific

C80.1 is a valid, billable ICD-10-CM code for malignant (primary) neoplasm, unspecified. It can be reported on claims for dates of service from October 1, 2026 – September 30, 2027.

Looking up by condition? See ICD-10 code for Malignant tumor.

Code unchanged since ICD-10-CM took effect on October 1, 2015. Source: official FY2027 ICD-10-CM release from CDC/NCHS and CMS. Page updated September 29, 2026. About our data

About C80.1

C80.1 is the ICD-10-CM diagnosis code for malignant (primary) neoplasm, unspecified. It belongs to category C80 (malignant neoplasm without specification of site), block C76-C80 (malignant neoplasms of ill-defined, other secondary and unspecified sites) and chapter 2 (neoplasms). It is billable, so it can be reported on its own for dates of service from October 1, 2026 through September 30, 2027.

Within C80, choose C80.1 (Malignant (primary) neoplasm, unspecified) only when documentation doesn't support a more specific option: disseminated malignant neoplasm, unspecified (C80.0) and malignant neoplasm associated with transplanted organ (C80.2).

Don't report C80.1 together with the conditions in its Excludes1 note: secondary malignant neoplasm of unspecified site (C79.9).

It is not a CC or MCC, so as a secondary diagnosis it doesn't change the MS-DRG severity level.

In MS-DRG v44.0, it is part of the grouping logic for DRG 826 (Myeloproliferative Disorders or Poorly Differentiated Neoplasms with Major O.R. Procedures with MCC, relative weight 4.7581), DRG 827 (Myeloproliferative Disorders or Poorly Differentiated Neoplasms with Major O.R. Procedures with CC, relative weight 2.3896), DRG 828 (Myeloproliferative Disorders or Poorly Differentiated Neoplasms with Major O.R. Procedures without CC/MCC, relative weight 1.6955), DRG 829 (Myeloproliferative Disorders or Poorly Differentiated Neoplasms with Other Procedures with CC/MCC, relative weight 3.1281), DRG 830 (Myeloproliferative Disorders or Poorly Differentiated Neoplasms with Other Procedures without CC/MCC, relative weight 1.4859), DRG 843 (Other Myeloproliferative Disorders or Poorly Differentiated Neoplastic Diagnoses with MCC, relative weight 1.9453) and 2 more, in MDC 17 (Myeloproliferative Diseases and Disorders, Poorly Differentiated Neoplasms), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.

It has been part of ICD-10-CM since the code set took effect on October 1, 2015 and hasn't changed since.

Before ICD-10, this condition was coded in ICD-9-CM as 199.1 (other malignant neoplasm without specification of site).

Coding notes

Applicable toConditions and synonyms classified to this code
  • Cancer NOS
  • Cancer unspecified site (primary)
  • Carcinoma unspecified site (primary)
  • Malignancy unspecified site (primary)
Excludes1Not coded here — never report together with this code
  • secondary malignant neoplasm of unspecified site (C79.9)

Notes that apply from higher levels

Instructions written at a parent level also apply to C80.1.

› From C80 Malignant neoplasm without specification of site
Excludes1
  • malignant carcinoid tumor of unspecified site (C7A.00)
  • malignant neoplasm of specified multiple sites- code to each site

Broader instructions also apply from Chapter 2: Neoplasms.

Alphabetic index entries

11 entries

Terms in the official ICD-10-CM index that lead to C80.1.

Table of Drugs & Neoplasms entries

Codes whose notes reference C80.1

MS-DRG v44.0 grouping

All DRGs →

Inpatient MS-DRGs this diagnosis can group to, as the principal or a secondary diagnosis, depending on the rest of the claim.

ICD-9-CM equivalent

Converter →
  • 199.1Other malignant neoplasm without specification of siteapproximate

From the CMS 2018 General Equivalence Mappings (GEMs), the final GEMs release.

Code history

  1. 2016
  2. 2017
  3. 2018
  4. 2019
  5. 2020
  6. 2021
  7. 2022
  8. 2023
  9. 2024
  10. 2025
  11. 2026
  12. 2027
  • FY2016 (effective 10/1/2015): Added (first year of ICD-10-CM)
  • No changes since FY2016.

Common questions about C80.1

Is C80.1 billable?

Yes. C80.1 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).

Can C80.1 be used as a principal diagnosis?

Yes. The Medicare Code Editor doesn't restrict C80.1 as a principal diagnosis.

Is C80.1 a CC or MCC?

No. C80.1 is neither a CC nor an MCC under MS-DRG v44.0.

What DRG does C80.1 group to?

C80.1 is used in the MS-DRG v44.0 logic for MS-DRG 826 (Myeloproliferative Disorders or Poorly Differentiated Neoplasms with Major O.R. Procedures with MCC), MS-DRG 827 (Myeloproliferative Disorders or Poorly Differentiated Neoplasms with Major O.R. Procedures with CC), MS-DRG 828 (Myeloproliferative Disorders or Poorly Differentiated Neoplasms with Major O.R. Procedures without CC/MCC), MS-DRG 829 (Myeloproliferative Disorders or Poorly Differentiated Neoplasms with Other Procedures with CC/MCC), MS-DRG 830 (Myeloproliferative Disorders or Poorly Differentiated Neoplasms with Other Procedures without CC/MCC), MS-DRG 843 (Other Myeloproliferative Disorders or Poorly Differentiated Neoplastic Diagnoses with MCC) and 2 more. Which one applies depends on whether it is the principal diagnosis and on the rest of the claim.

What is the ICD-9 code for C80.1?

The CMS General Equivalence Mappings map C80.1 to ICD-9-CM 199.1.