What is ICD-10 code C71.9?

C71.9 is the ICD-10-CM diagnosis code for Malignant neoplasm of brain, unspecified. It belongs to the ICD-10-CM chapter for neoplasms (c00-d49). C71.9 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. C71.9 is part of the FY2026 ICD-10-CM code set published by the CMS National Center for Health Statistics and used on Medicare, Medicaid, and commercial claims in the United States.

Yes. C71.9 is a billable ICD-10-CM code that can be reported on professional and institutional claims as a primary or secondary diagnosis when the provider documentation supports the specific condition described. Billable codes in ICD-10-CM are coded to the highest level of specificity available for the documented diagnosis. C71.9 is current for fiscal year 2026 and remains in the active CMS ICD-10-CM code set published by the National Center for Health Statistics.

What is the V28 vs V24 difference for C71.9?

CMS phased in the V28 risk adjustment model over payment years 2024 (33%), 2025 (67%), and 2026 (100%), replacing V24. V28 consolidates HCC categories, removes some lower-acuity conditions, and recalibrates RAF weights across the entire model. For C71.9, V28 maps to Lung and Other Severe Cancers at RAF 0.000 while V24 mapped to Lymphoma and Other Cancers at RAF 0.675. Both models can still appear in legacy data and in payer-specific lookback periods.

What should coders know when reporting C71.9?

Query the physician if more specific anatomical location is available, as codes C71.0-C71.8 provide more precise localization (cerebrum, cerebellum, brainstem, etc.) and may affect treatment planning and prognosis Ensure documentation includes whether this is a primary brain cancer or metastatic cancer that has spread to the brain, as metastatic cancers use different code categories (C79.31) Because C71.9 maps to a payment HCC, the documentation must also satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's risk adjustment score.

C71.9 ICD-10 Code: Malignant neoplasm of brain,

ICD-10-CM Code View

HCC Buddy Code Card

Digital ICD-10 code-book layout with official code detail, always-visible risk models, Code Trumping, and Buddy coding guidance.

Code lookupC71.9Effective periodFY2026 Apr Update (Apr 1-Sep 30)

FY 2026 Apr update / Neoplasms (C00-D49) / Malignant neoplasms of eye, brain and other parts of central nervous system (C69-C72)

C71.9

Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidance

Malignant neoplasm of brain, unspecified

This code represents a cancer that has started in the brain, but the specific location within the brain has not been identified or documented. It is used when a patient has been diagnosed with brain cancer without more detailed information about which part of the brain is affected.

Buddy Insight

This unspecified brain cancer code is used when a malignant brain tumor has been confirmed but the specific location within the brain has not been documented.

CMS-HCC V28

Mapped

HCC 20

Lung and Other Severe Cancers

RAF 0.0

CMS-HCC V24

Mapped

HCC 10

Lymphoma and Other Cancers

RAF 0.675

ACA/HHS

Not risk-adjusted for this model/period.

RAF 0

ESRD/PACE

Mapped

HCC 10

Lymphoma and Other Cancers

RAF 0.0

RXHCC

Mapped

HCC 22

Cancer, Other Specified Sites

RAF 0.0

Code Trumping

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Compare selected patient codes to show trumped or trumps impact.

Code Book Path

Official

C71Malignant neoplasm of brain

C71.9Malignant neoplasm of brain, unspecified

Inclusion Terms

Official

ICD-10-CM does not list inclusion terms for C71.9 in this effective period.

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for C71.9 in this effective period.

Related Child Codes

Official

C71.0Malignant neoplasm of cerebrum, except lobes and ventricles

C71.1Malignant neoplasm of frontal lobe

C71.2Malignant neoplasm of temporal lobe

C71.3Malignant neoplasm of parietal lobe

C71.4Malignant neoplasm of occipital lobe

Includes

Official

ICD-10-CM does not list Includes notes for C71.9 in this effective period.

Excludes 1

Official

malignant neoplasm of cranial nerves (C72.2-C72.5)
retrobulbar malignant neoplasm (C69.6-)

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for C71.9 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for C71.9 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for C71.9 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance

Confirmed malignant brain neoplasm by pathology or definitive imaging

Documentation that more specific location information was sought but unavailable

Evidence of provider query for specificity

Treatment status and clinical stage

MEAT Support

HCC Buddy guidance

Confirmed malignant brain neoplasm by pathology or definitive imaging

Documentation that more specific location information was sought but unavailable

Evidence of provider query for specificity

Treatment status and clinical stage

Audit Caution

HCC Buddy guidance

Defaulting to C71.9 without reviewing MRI or operative reports that almost always specify the brain region

Coding brain metastases as primary brain cancer (C71.9) instead of C79.31 — this is one of the most common coding errors in neuro-oncology

Using this code when pathology clearly identifies a lobe-specific tumor

Not recognizing that brain cancer specificity does not change HCC weight but does affect data quality and audit compliance

Common Mistakes

HCC Buddy guidance

C71.0-C71.8 — Specific brain location codes: always review imaging and surgical reports for location before defaulting to C71.9

C79.31 — Secondary brain malignancy: brain metastases from other cancers are extremely common and should not be coded as primary brain cancer

D43.2 — Brain neoplasm of uncertain behavior: use only when malignancy is not confirmed

D33.2 — Benign brain neoplasm: confirm malignant diagnosis before using C71 codes

Last updated: FY2026 ICD-10-CM Apr update, Apr 1, 2026 through Sep 30, 2026. CMS-HCC V28 is 100% phased in for payment year 2026.

Is C71.9 an HCC code?

Yes. C71.9 maps to Lung and Other Severe Cancers under the CMS-HCC V28 risk adjustment model (and Lymphoma and Other Cancers under V24).

HCC Category Mapping

V28HCC 20 — Lung and Other Severe Cancers

0.000

V24HCC 10 — Lymphoma and Other Cancers

0.675

ESRDHCC 10 — Lymphoma and Other Cancers

0.000

RxHCCHCC 22 — Cancer, Other Specified Sites

0.000

RAF weights shown are the community, non-dual, aged base weights from the CMS risk adjustment model file. Actual per-patient RAF contribution depends on member segment, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains in use during the transition and for historical data.

MEAT Criteria for C71.9

For C71.9to count as a valid HCC diagnosis in a given encounter, the provider's documentation must show MEAT: Monitor, Evaluate, Assess, or Treat. A diagnosis from a prior year does not carry forward automatically — it has to be re-documented and supported each calendar year.

MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
EEvaluate: test results, medication response, or physical findings reviewed by the provider
AAssess: explicit mention in the assessment or plan with acknowledgment of status
TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis

Only one of M/E/A/T is required to support the code, but the documentation must be specific enough to show that the provider actually addressed C71.9 during that encounter — not just copy-forwarded from a problem list.

What This Code Means

C71.9 is the ICD-10-CM diagnosis code for malignant neoplasm of brain, unspecified. This code represents a cancer that has started in the brain, but the specific location within the brain has not been identified or documented. It is used when a patient has been diagnosed with brain cancer without more detailed information about which part of the brain is affected. C71.9 sits in the ICD-10-CM chapter for neoplasms (c00-d49), within the section covering malignant neoplasms of eye, brain and other parts of central nervous system (c69-c72).

Under the CMS-HCC V28 risk adjustment model, C71.9 maps to Lung and Other Severe Cancers (HCC 20) with a community, non-dual, aged base RAF weight of 0.000. Under the older CMS-HCC V24 model, C71.9 maps to Lymphoma and Other Cancers (HCC 10) with a community, non-dual, aged base RAF weight of 0.675. V28 is the CMS-HCC risk adjustment model that reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition.

Query the physician if more specific anatomical location is available, as codes C71.0-C71.8 provide more precise localization (cerebrum, cerebellum, brainstem, etc.) and may affect treatment planning and prognosis. Because C71.9 maps to a payment HCC, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's Medicare Advantage risk adjustment score. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.

HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for C71.9 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•Query the physician if more specific anatomical location is available, as codes C71.0-C71.8 provide more precise localization (cerebrum, cerebellum, brainstem, etc.) and may affect treatment planning and prognosis
•Ensure documentation includes whether this is a primary brain cancer or metastatic cancer that has spread to the brain, as metastatic cancers use different code categories (C79.31)

Clinical Significance

This unspecified brain cancer code is used when a malignant brain tumor has been confirmed but the specific location within the brain has not been documented. While it captures the cancer diagnosis for risk adjustment at the same HCC weight, it represents a significant documentation gap given that MRI or surgical reports nearly always identify the tumor location.

Documentation Requirements

✓Confirmed malignant brain neoplasm by pathology or definitive imaging
✓Documentation that more specific location information was sought but unavailable
✓Evidence of provider query for specificity
✓Treatment status and clinical stage
✓Histological type if pathology has been performed

Commonly Confused Codes

•C71.0-C71.8 — Specific brain location codes: always review imaging and surgical reports for location before defaulting to C71.9
•C79.31 — Secondary brain malignancy: brain metastases from other cancers are extremely common and should not be coded as primary brain cancer
•D43.2 — Brain neoplasm of uncertain behavior: use only when malignancy is not confirmed
•D33.2 — Benign brain neoplasm: confirm malignant diagnosis before using C71 codes