2027 ICD-10-CM Diagnosis Code C79.31Secondary malignant neoplasm of brain

ICD-10-CM Codes›C00–D49›C76-C80›C79

ICD-10-CM C79.31
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

C79.31 is a billable ICD-10-CM diagnosis code for secondary malignant neoplasm of brain. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 54 through 55. As a secondary diagnosis, it counts as a complication or comorbidity (CC) and moves an inpatient stay to a higher severity level within its MS-DRG family. It does not count, however, when the principal diagnosis is one of 20 closely related codes. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Secondary malignancies.

For Medicare Advantage risk adjustment, C79.31 maps to CMS-HCC Category 17 (Cancer Metastatic to Lung, Liver, Brain, and Other Organs; Acute Myeloid Leukemia Except Promyelocytic) under the V28 model, adding a risk factor of about 4.209 for a community, non-dual, aged beneficiary in payment year 2027.

Code Identity

ICD-10-CM Code
C79.31
Billable Status
Yes — Valid for Submission
Code Describes
Secondary malignant neoplasm of brain
Short Description
Secondary malignant neoplasm of brain
Same as the full description in the CMS dataset.
Parent Code
C79.3
Secondary malignant neoplasm of brain and cerebral meninges

Code Classification

ChapterC00–D49Neoplasms
SectionC76-C80Malignant neoplasms of ill-defined, other secondary and unspecified sites
CategoryC79Secondary malignant neoplasm of other and unspecified sites
This CodeC79.31Secondary malignant neoplasm of brain

Medicare Risk Adjustment (HCC)Billing

C79.31 maps to a payment category in the CMS-HCC model used to risk-adjust Medicare Advantage payments. Weights are the published community factors for payment year 2027.

CMS-HCC V28 Category (Payment Model)
HCC 17— Cancer Metastatic to Lung, Liver, Brain, and Other Organs; Acute Myeloid Leukemia Except Promyelocytic
Payment HCC · PY 2027 one of 78 ICD-10-CM codes in this category
Risk Adjustment Factor (RAF) Weight
+4.209
community, non-dual, aged · ranges 1.952–4.235 across segments
Hierarchy
Supersedes HCC 18, HCC 19, HCC 20, HCC 21, HCC 22, and HCC 23
less severe related categories are not paid alongside HCC 17
Prior Model (CMS-HCC V24)
HCC 8
V24 retired V28 pays 100% of MA risk scores since PY 2026
Other CMS Models
PACE (CMS-HCC V22): HCC 8 · ESRD (V21): HCC 8 · ESRD (V24): HCC 8
ESRD V21 weights: 0.295 dialysis, 1.289–2.627 functioning graft · ESRD V24 weights: 0.353 dialysis, 1.571–3.226 functioning graft
Part D (RxHCC)
RxHCC 18 — Secondary Cancer of Lung, Liver, Brain, and Other Sites
also risk-adjusts in the Part D prescription drug model (V08)

Source: CMS Payment Year 2027 risk adjustment mappings and model software. Weights are relative factors, not dollar amounts; a beneficiary's total RAF also includes demographics and interactions. Browse all CMS-HCC categories.

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Dementia due to metastatic malignant neoplasm to brain
  • Malignant neoplasm of basal ganglia
  • Malignant neoplasm of cerebellum
  • Malignant neoplasm of frontal lobe
  • Malignant neoplasm of occipital lobe
  • Malignant neoplasm of parietal lobe
  • Malignant neoplasm of temporal lobe
  • Malignant neoplasm of ventricle of brain
  • Metastatic malignant neoplasm to brain
  • Metastatic malignant neoplasm to brain and spinal cord
  • Metastatic malignant neoplasm to brain stem
  • Metastatic malignant neoplasm to brain ventricle
  • Metastatic malignant neoplasm to cerebellum
  • Metastatic malignant neoplasm to cerebrum
  • Metastatic malignant neoplasm to frontal lobe
  • Metastatic malignant neoplasm to occipital lobe
  • Metastatic malignant neoplasm to parietal lobe
  • Metastatic malignant neoplasm to spinal cord
  • Metastatic malignant neoplasm to temporal lobe
  • Metastatic neoplasm of left basal ganglia
  • Metastatic neoplasm of right basal ganglia
  • Metastatic neuroblastoma
  • Metastatic neuroblastoma to brain
  • Metastatic neuroblastoma to central nervous system
  • Neuroblastoma of brain
  • Neuroblastoma of central nervous system

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to C79.31: its own notes plus those printed at C79 and Chapter 2. A note printed at a category, block or chapter applies to every code under it.

Excludes1

Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.

From C79 Secondary malignant neoplasm of other and unspecified sites applies to 25 codes
  • secondary carcinoid tumors (C7B.-)
  • secondary neuroendocrine tumors (C7B.-)

Notes

General instructions on how these codes are used.

From Chapter 2 (C00-D49) Neoplasms applies to 1,730 codes
  • Functional activity
  • All neoplasms are classified in this chapter, whether they are functionally active or not. An additional code from Chapter 4 may be used, to identify functional activity associated with any neoplasm.
  • Morphology [Histology]
  • Chapter 2 classifies neoplasms primarily by site (topography), with broad groupings for behavior, malignant, in situ, benign, etc. The Table of Neoplasms should be used to identify the correct topography code. In a few cases, such as for malignant melanoma and certain neuroendocrine tumors, the morphology (histologic type) is included in the category and codes.
  • Primary malignant neoplasms overlapping site boundaries
  • A primary malignant neoplasm that overlaps two or more contiguous (next to each other) sites should be classified to the subcategory/code .8 ('overlapping lesion'), unless the combination is specifically indexed elsewhere. For multiple neoplasms of the same site that are not contiguous, such as tumors in different quadrants of the same breast, codes for each site should be assigned.
  • Malignant neoplasm of ectopic tissue
  • Malignant neoplasms of ectopic tissue are to be coded to the site mentioned, e.g., ectopic pancreatic malignant neoplasms are coded to pancreas, unspecified (C25.9).

Source: CMS ICD-10-CM Tabular List. How to read instructional notes.

Referenced in Other NotesGuidance

Instructional notes printed at other codes that name C79.31, its category, or a range that includes it.

Applicable To 2

These notes mention C79.31.

  • Z85.8 Personal history of malignant neoplasms of other organs and systems
    Conditions classifiable to C00-C14, C40-C49, C69-C75, C7A.098, C76-C79 names C76-C79, which includes this code
  • Z85.89 Personal history of malignant neoplasm of other organs and systems
    Conditions classifiable to C7A.098, C76, C77-C79 names C77-C79, which includes this code

Clinical ClassificationClinical

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

CCSR NEO070
Secondary malignancies
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Metastatic Malignant Neoplasm to the Brain

    a malignant neoplasm that has spread to the brain from another anatomic site or system. the majority are carcinomas (usually lung or breast carcinomas).

Table of NeoplasmsClinical

Anatomical sites in the Table of Neoplasms that reference this code family.

SiteMalig.
Primary		Malig.
Secondary		Ca
in situ		BenignUncertainUnspec.
basal gangliaC71.0C79.31–D33.0D43.0D49.6
basis pedunculiC71.7C79.31–D33.1D43.1D49.6
brain NECC71.9C79.31–D33.2D43.2D49.6
brain NEC › basal gangliaC71.0C79.31–D33.0D43.0D49.6
brain NEC › cerebellopontine angleC71.6C79.31–D33.1D43.1D49.6
brain NEC › cerebellum NOSC71.6C79.31–D33.1D43.1D49.6
brain NEC › cerebrumC71.0C79.31–D33.0D43.0D49.6
brain NEC › choroid plexusC71.7C79.31–D33.1D43.1D49.6
brain NEC › corpus callosumC71.8C79.31–D33.2D43.2D49.6
brain NEC › corpus striatumC71.0C79.31–D33.0D43.0D49.6
brain NEC › cortex (cerebral)C71.0C79.31–D33.0D43.0D49.6
brain NEC › frontal lobeC71.1C79.31–D33.0D43.0D49.6
brain NEC › globus pallidusC71.0C79.31–D33.0D43.0D49.6
brain NEC › hippocampusC71.2C79.31–D33.0D43.0D49.6
brain NEC › hypothalamusC71.0C79.31–D33.0D43.0D49.6
brain NEC › internal capsuleC71.0C79.31–D33.0D43.0D49.6
brain NEC › medulla oblongataC71.7C79.31–D33.1D43.1D49.6
brain NEC › midbrainC71.7C79.31–D33.1D43.1D49.6
brain NEC › occipital lobeC71.4C79.31–D33.0D43.0D49.6
brain NEC › overlapping lesionC71.8C79.31––––
brain NEC › parietal lobeC71.3C79.31–D33.0D43.0D49.6
brain NEC › peduncleC71.7C79.31–D33.1D43.1D49.6
brain NEC › ponsC71.7C79.31–D33.1D43.1D49.6
brain NEC › stemC71.7C79.31–D33.1D43.1D49.6
brain NEC › tapetumC71.8C79.31–D33.2D43.2D49.6
brain NEC › temporal lobeC71.2C79.31–D33.0D43.0D49.6
brain NEC › thalamusC71.0C79.31–D33.0D43.0D49.6
brain NEC › uncusC71.2C79.31–D33.0D43.0D49.6
brain NEC › ventricle (floor)C71.5C79.31–D33.0D43.0D49.6
brain NEC › ventricle (floor) › fourthC71.7C79.31–D33.1D43.1D49.6
cerebellopontine (angle)C71.6C79.31–D33.1D43.1D49.6
cerebellum, cerebellarC71.6C79.31–D33.1D43.1D49.6
cerebrum, cerebral (cortex) (hemisphere) (white matter)C71.0C79.31–D33.0D43.0D49.6
cerebrum, cerebral (cortex) (hemisphere) (white matter) › peduncleC71.7C79.31–D33.1D43.1D49.6
cerebrum, cerebral (cortex) (hemisphere) (white matter) › ventricleC71.5C79.31–D33.0D43.0D49.6
cerebrum, cerebral (cortex) (hemisphere) (white matter) › ventricle › fourthC71.7C79.31–D33.1D43.1D49.6
choroid › plexusC71.5C79.31–D33.0D43.0D49.6
corpus › callosum, brainC71.0C79.31–D33.2D43.2D49.6
corpus › striatum, cerebrumC71.0C79.31–D33.0D43.0D49.6
cortex › cerebralC71.0C79.31–D33.0D43.0D49.6
cranial (fossa, any)C71.9C79.31–D33.2D43.2D49.6
ependyma (brain)C71.5C79.31–D33.0D43.0D49.6
ependyma (brain) › fourth ventricleC71.7C79.31–D33.1D43.1D49.6
fossa (of) › anterior (cranial)C71.9C79.31–D33.2D43.2D49.6
fossa (of) › cranialC71.9C79.31–D33.2D43.2D49.6
fossa (of) › middle (cranial)C71.9C79.31–D33.2D43.2D49.6
fossa (of) › posterior (cranial)C71.9C79.31–D33.2D43.2D49.6
frontal › lobe, brainC71.1C79.31–D33.0D43.0D49.6
frontal › poleC71.1C79.31–D33.0D43.0D49.6
ganglia [See Also: Neoplasm, nerve, peripheral] › basalC71.0C79.31–D33.0D43.0D49.6
globus pallidusC71.0C79.31–D33.0D43.0D49.6
hemisphere, cerebralC71.0C79.31–D33.0D43.0D49.6
hippocampus, brainC71.2C79.31–D33.0D43.0D49.6
hypothalamusC71.0C79.31–D33.0D43.0D49.6
insulaC71.0C79.31–D33.0D43.0D49.6
insular tissue (pancreas) › brainC71.0C79.31–D33.0D43.0D49.6
internal › capsuleC71.0C79.31–D33.0D43.0D49.6
intracranial NECC71.9C79.31–D33.2D43.2D49.6
island of ReilC71.0C79.31–D33.0D43.0D49.6
medulla › oblongataC71.7C79.31–D33.1D43.1D49.6
midbrainC71.7C79.31–D33.1D43.1D49.6
motor tract › brainC71.9C79.31–D33.2D43.2D49.6
occipital › lobe or pole, brainC71.4C79.31–D33.0D43.0D49.6
olive (brain)C71.7C79.31–D33.1D43.1D49.6
operculum (brain)C71.0C79.31–D33.0D43.0D49.6
palliumC71.0C79.31–D33.0D43.0D49.6
parietal › lobe, brainC71.3C79.31–D33.0D43.0D49.6
peduncle, cerebralC71.7C79.31–D33.1D43.1D49.6
plexus › choroidC71.5C79.31–D33.0D43.0D49.6
pole › frontalC71.1C79.31–D33.0D43.0D49.6
pole › occipitalC71.4C79.31–D33.0D43.0D49.6
pons (varolii)C71.7C79.31–D33.1D43.1D49.6
posterior fossa (cranial)C71.9C79.31–D33.2D43.2D49.6
putamenC71.0C79.31–D33.0D43.0D49.6
pyramid (brain)C71.7C79.31–D33.1D43.1D49.6
rhinencephalonC71.0C79.31–D33.0D43.0D49.6
spine, spinal (column) › bulbC71.7C79.31–D33.1D43.1D49.6
stem, brainC71.7C79.31–D33.1D43.1D49.6
suprasellar (region)C71.9C79.31–D33.2D43.2D49.6
supratentorial (brain) NECC71.0C79.31–D33.0D43.0D49.6
tapetum, brainC71.8C79.31–D33.2D43.2D49.6
temporal › lobe or poleC71.2C79.31–D33.0D43.0D49.6
thalamusC71.0C79.31–D33.0D43.0D49.6
uncus, brainC71.2C79.31–D33.0D43.0D49.6
ventricle (cerebral) (floor) (lateral) (third)C71.5C79.31–D33.0D43.0D49.6
ventricle (cerebral) (floor) (lateral) (third) › fourthC71.7C79.31–D33.1D43.1D49.6
vermis, cerebellumC71.6C79.31–D33.1D43.1D49.6
white matter (central) (cerebral)C71.0C79.31–D33.0D43.0D49.6

Patient EducationClinical

Brain Tumors

A brain tumor is a growth of abnormal cells in the tissues of the brain. Brain tumors can be benign, with no cancer cells, or malignant, with cancer cells that grow quickly. Some are primary brain tumors, which start in the brain. Others are metastatic, and they start somewhere else in the body and move to the brain.

Read the full article at MedlinePlus

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

Convert C79.31 to ICD-9-CMHistory

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

ICD-9-CM
198.3 Sec mal neo brain/spine
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 2017–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About C79.31Overview

What is the ICD-10 code for secondary malignant neoplasm of brain?

The ICD-10-CM code for secondary malignant neoplasm of brain is C79.31 (sometimes written as C7931). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

Is C79.31 (Secondary malignant neoplasm of brain and cerebral meninges) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report secondary malignant neoplasm of brain on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

What MS-DRG does C79.31 group to?

When secondary malignant neoplasm of brain is the principal diagnosis on an inpatient stay, it groups to MS-DRG 55, 54, with relative weights from 1.0291 to 1.5197 depending on complications. Higher weights mean higher Medicare reimbursement.

Is C79.31 a CC or MCC?

CMS lists C79.31 as a CC (complication or comorbidity) for FY 2027. Reported as a secondary diagnosis, it moves the inpatient stay to a higher-weighted DRG within its severity family. It does not count when the principal diagnosis is one of the 20 closely related codes in its exclusion list.

Can C79.31 be reported with a code from C7B?

Not as a rule. The Excludes1 note at C79, which applies to C79.31, lists "secondary carcinoid tumors (C7B.-)". An Excludes1 note means the excluded code is never reported together with this one; the only exception is when the two conditions are unrelated to each other (Official Guidelines, Section I.A.12.a).

What HCC is C79.31?

C79.31 (secondary malignant neoplasm of brain) maps to CMS-HCC Category 17 (Cancer Metastatic to Lung, Liver, Brain, and Other Organs; Acute Myeloid Leukemia Except Promyelocytic), commonly written as HCC 17, in the CMS-HCC V28 model used for Medicare Advantage risk adjustment in payment year 2027. It mapped to HCC 8 under the retired V24 model. It also maps in the PACE (CMS-HCC V22), ESRD (V21), and ESRD (V24) models. In the Part D prescription drug model it maps to RxHCC 18.

Does C79.31 risk-adjust for Medicare Advantage payment?

Yes. When documented and reported on a Medicare Advantage encounter, C79.31 adds a risk adjustment factor of about 4.209 to the beneficiary's RAF score for a community, non-dual, aged enrollee (published V28 weights range from 1.952 to 4.235 depending on the payment segment). HCC 17 sits at the top of its hierarchy, so no other condition category supersedes it. See the full factor table on the HCC 17 category page.