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ICD-10-CM 2027 diagnosis code

C79.9Secondary malignant neoplasm of unspecified site

✓ Billable / specificCC — complication/comorbidity

C79.9 is a valid, billable ICD-10-CM code for secondary malignant neoplasm of unspecified site. It can be reported on claims for dates of service from October 1, 2026 – September 30, 2027.

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 C79.9

C79.9 is the ICD-10-CM diagnosis code for secondary malignant neoplasm of unspecified site. It belongs to category C79 (secondary malignant neoplasm of other and unspecified sites), 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 C79, choose C79.9 (unspecified site) only when documentation doesn't support a more specific option: kidney and renal pelvis (C79.0), bladder and other and unspecified urinary organs (C79.1), skin (C79.2), brain and cerebral meninges (C79.3), other and unspecified parts of nervous system (C79.4), bone and bone marrow (C79.5), ovary (C79.6), adrenal gland (C79.7) and 1 more.

Don't report C79.9 together with the conditions in its Excludes1 note: carcinomatosis NOS (C80.0), generalized cancer NOS (C80.0) and malignant (primary) neoplasm of unspecified site (C80.1).

As a secondary diagnosis it is a CC (complication or comorbidity), which can move an inpatient stay into the "with CC" MS-DRG of its family, unless the principal diagnosis excludes it.

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 198.89 (secondary malignant neoplasm of other specified sites).

Coding notes

Applicable toConditions and synonyms classified to this code
  • Metastatic cancer NOS
  • Metastatic disease NOS
Excludes1Not coded here — never report together with this code
  • carcinomatosis NOS (C80.0)
  • generalized cancer NOS (C80.0)
  • malignant (primary) neoplasm of unspecified site (C80.1)

Notes that apply from higher levels

Instructions written at a parent level also apply to C79.9.

› From C79 Secondary malignant neoplasm of other and unspecified sites
Excludes1
  • secondary carcinoid tumors (C7B.-)
  • secondary neuroendocrine tumors (C7B.-)

Broader instructions also apply from Chapter 2: Neoplasms.

Alphabetic index entries

2 entries

Terms in the official ICD-10-CM index that lead to C79.9.

Table of Drugs & Neoplasms entries

Codes whose notes reference C79.9

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 →
  • 198.89Secondary malignant neoplasm of other specified sitesapproximate

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 C79.9

Is C79.9 billable?

Yes. C79.9 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).

Can C79.9 be used as a principal diagnosis?

Yes. The Medicare Code Editor doesn't restrict C79.9 as a principal diagnosis.

Is C79.9 a CC or MCC?

C79.9 is a CC (complication or comorbidity) under MS-DRG v44.0, unless excluded by the principal diagnosis.

What DRG does C79.9 group to?

C79.9 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 C79.9?

The CMS General Equivalence Mappings map C79.9 to ICD-9-CM 198.89.