What is ICD-10 code C71.1?

C71.1 is the ICD-10-CM diagnosis code for Malignant neoplasm of frontal lobe. Cancer that develops in the frontal lobe of the brain, which controls personality, decision-making, and movement. This is a malignant brain tumor in the front part of the cerebrum. C71.1 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. C71.1 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. C71.1 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. C71.1 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 C71.1?

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 C71.1, V28 maps to Lung and Other Severe Cancers at RAF 1.136 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 C71.1?

Confirm documentation specifies frontal lobe location to differentiate from other cerebral lobes Note laterality (left or right) when documented, as this impacts surgical planning Because C71.1 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.

2026 ICD-10-CM C71.1: Malignant neoplasm of frontal

ICD-10-CM Code View

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Code lookupC71.1Effective 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)

C71.1

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

Malignant neoplasm of frontal lobe

Cancer that develops in the frontal lobe of the brain, which controls personality, decision-making, and movement. This is a malignant brain tumor in the front part of the cerebrum.

Buddy Insight

Frontal lobe malignancy affects the brain region controlling executive function, personality, motor planning, and expressive language (Broca's area on the dominant side).

CMS-HCC V28

Mapped

HCC 20

Lung and Other Severe Cancers

RAF 1.136

CMS-HCC V24

Mapped

HCC 10

Lymphoma and Other Cancers

RAF 0.675

ACA/HHS

Mapped

HCC 9

HHS-HCC 9

Varies by metal level

ESRD/PACE

Mapped

HCC 10

Lymphoma and Other Cancers

RAF 0.111

RXHCC

Mapped

HCC 22

Cancer, Other Specified Sites

RAF 0.124

Code Book Path

Official

C71Malignant neoplasm of brain

C71.1Malignant neoplasm of frontal lobe

Inclusion Terms

Official

ICD-10-CM does not list inclusion terms for C71.1 in this effective period.

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for C71.1 in this effective period.

Related Child Codes

Official

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

C71.2Malignant neoplasm of temporal lobe

C71.3Malignant neoplasm of parietal lobe

C71.4Malignant neoplasm of occipital lobe

C71.5Malignant neoplasm of cerebral ventricle

Includes

Official

ICD-10-CM does not list Includes notes for C71.1 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 C71.1 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for C71.1 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for C71.1 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance

Pathology confirming malignancy with histological type and World Health Organization grade

MRI brain documenting frontal lobe location

Laterality (right versus left hemisphere) when documented, as this affects neurological presentation

Molecular marker results (IDH, MGMT, 1p/19q)

MEAT Support

HCC Buddy guidance

Pathology confirming malignancy with histological type and World Health Organization grade

MRI brain documenting frontal lobe location

Laterality (right versus left hemisphere) when documented, as this affects neurological presentation

Molecular marker results (IDH, MGMT, 1p/19q)

Audit Caution

HCC Buddy guidance

Using the general cerebrum code C71.0 when documentation specifies frontal lobe

Coding metastatic cancer to the frontal lobe as primary frontal lobe cancer

Failing to code C71.8 (overlapping) when the tumor crosses from frontal to adjacent lobes

Not documenting or querying for laterality, which is clinically significant for surgical planning

Common Mistakes

HCC Buddy guidance

C71.2 — Temporal lobe: frontotemporal tumors spanning both lobes may require C71.8 (overlapping)

C71.0 — Cerebrum, except lobes: use C71.1 when documentation specifies frontal lobe

C71.8 — Overlapping sites: use when tumor extends across frontal and adjacent lobes

C79.31 — Brain metastasis: confirm this is a primary brain cancer, not a metastatic lesion to the frontal lobe

Current with CMS: FY2026 ICD-10-CM Apr 1 update (effective Apr 1 – Sep 30, 2026) · CMS-HCC V28, 100% phased in for payment year 2026. FY2027 code set already staged for October 1, 2026. How HCC Buddy stays current →

Is C71.1 an HCC code?

Yes. C71.1 (Malignant neoplasm of frontal lobe) maps to Lung and Other Severe Cancers under the CMS-HCC V28 risk adjustment model (and Lymphoma and Other Cancers under V24), with a community non-dual aged RAF of 1.136. It is billable for payment year 2026.

Coder answer: C71.1 is billable and maps to V28 HCC 20, Lung and Other Severe Cancers. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.

Code: C71.1
Description: Malignant neoplasm of frontal lobe
HCC (V28): HCC 20 — Lung and Other Severe Cancers
RAF: 1.136
Billable: Yes
Payment year: 2026

HCC Category Mapping

V28HCC 20, Lung and Other Severe Cancers

1.136

V24HCC 10, Lymphoma and Other Cancers

0.675

ESRDHCC 10, Lymphoma and Other Cancers

0.111

RxHCCHCC 22, Cancer, Other Specified Sites

0.124

Each model's RAF is its CMS base weight for that model's standard population, so weights are not directly comparable across models: CMS-HCC V28 and V24 use Community, Non-Dual, Aged; ESRD uses the dialysis continuing-enrollee model; RxHCC is the Part D continuing-enrollee, non-low-income, aged weight (a larger scale than CMS-HCC). ACA/HHS has no single weight — it varies by metal level. 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.

Work C71.1 in the Code Book — tabular path, V28 RAF, and MEAT checklist →

MEAT Criteria for C71.1

For C71.1 to 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 C71.1 during that encounter, not just copy-forwarded from a problem list.

Coder workflow notes

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What This Code Means

C71.1 is the ICD-10-CM diagnosis code for malignant neoplasm of frontal lobe. Cancer that develops in the frontal lobe of the brain, which controls personality, decision-making, and movement. This is a malignant brain tumor in the front part of the cerebrum. C71.1 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, C71.1 maps to Lung and Other Severe Cancers (HCC 20) with a community, non-dual, aged base RAF weight of 1.136. Under the older CMS-HCC V24 model, C71.1 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.

Confirm documentation specifies frontal lobe location to differentiate from other cerebral lobes. Because C71.1 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 C71.1 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•Confirm documentation specifies frontal lobe location to differentiate from other cerebral lobes
•Note laterality (left or right) when documented, as this impacts surgical planning

Clinical Significance

Frontal lobe malignancy affects the brain region controlling executive function, personality, motor planning, and expressive language (Broca's area on the dominant side). These tumors can cause profound personality changes, motor deficits, and speech impairment. Frontal lobe glioblastoma is one of the most common primary brain cancers and carries a poor prognosis despite aggressive multimodal treatment.

Documentation Requirements

✓Pathology confirming malignancy with histological type and World Health Organization grade
✓MRI brain documenting frontal lobe location
✓Laterality (right versus left hemisphere) when documented, as this affects neurological presentation
✓Molecular marker results (IDH, MGMT, 1p/19q)
✓Assessment of functional status and neurological deficits

Commonly Confused Codes

•C71.2: Temporal lobe: frontotemporal tumors spanning both lobes may require C71.8 (overlapping)
•C71.0: Cerebrum, except lobes: use C71.1 when documentation specifies frontal lobe
•C71.8: Overlapping sites: use when tumor extends across frontal and adjacent lobes
•C79.31: Brain metastasis: confirm this is a primary brain cancer, not a metastatic lesion to the frontal lobe