C71.5
BillableMalignant neoplasm of cerebral ventricle
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is C71.5 an HCC code?
Yes. C71.5 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 C71.5
For C71.5 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 C71.5 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
C71.5 is the ICD-10-CM diagnosis code for malignant neoplasm of cerebral ventricle. A malignant (cancerous) tumor that originates in the cerebral ventricles, which are fluid-filled spaces within the brain. This is a serious brain cancer that requires immediate medical attention and treatment. C71.5 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, C71.5 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, C71.5 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.
Verify the histological type of the neoplasm from the pathology report, as additional characters may be needed to specify behavior (malignant, in situ, etc.) and laterality if applicable. Because C71.5 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 C71.5 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Verify the histological type of the neoplasm from the pathology report, as additional characters may be needed to specify behavior (malignant, in situ, etc.) and laterality if applicable
- •Ensure this code is used only for primary malignant tumors of the cerebral ventricles; use different codes for metastatic cancers to the ventricles or benign tumors
Clinical Significance
Cerebral ventricular malignancy includes tumors arising within the fluid-filled cavities of the brain, such as choroid plexus carcinoma, ependymoma, and central neurocytoma. These tumors can obstruct cerebrospinal fluid flow causing hydrocephalus, and may require emergent intervention for raised intracranial pressure in addition to definitive cancer treatment.
Documentation Requirements
- ✓Pathology confirming malignancy with specific histological type (choroid plexus carcinoma, ependymoma, subependymoma)
- ✓MRI brain documenting the specific ventricle involved (lateral, third, fourth)
- ✓Assessment for hydrocephalus and intracranial pressure
- ✓Cerebrospinal fluid analysis if obtained
- ✓Distinction from benign ventricular tumors
Excludes 1 — Do NOT code together
- malignant neoplasm of fourth cerebral ventricle (C71.7)
Commonly Confused Codes
- •C71.0 — Cerebrum except lobes and ventricles: C71.0 explicitly excludes ventricles — use C71.5 for ventricular tumors
- •C71.6 — Cerebellum: fourth ventricle tumors are at the cerebellum border; verify if the tumor is intraventricular or cerebellar
- •D33.0 — Benign neoplasm of brain: benign ventricular tumors should not use C71.5
- •C71.7 — Brain stem: fourth ventricle floor tumors may extend into the brain stem