C71.1
BillableMalignant neoplasm of frontal lobe
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is C71.1 an HCC code?
Yes. C71.1 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
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 C71.1
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.
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 0.000. 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