C71.6
BillableMalignant neoplasm of cerebellum
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is C71.6 an HCC code?
Yes. C71.6 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 C71.6
For C71.6 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 C71.6 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
C71.6 is the ICD-10-CM diagnosis code for malignant neoplasm of cerebellum. Cancer that develops in the cerebellum, the part of the brain that controls balance and coordination. This is a malignant tumor in the lower back part of the brain. C71.6 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, C71.6 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, C71.6 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.
Ensure documentation clearly identifies the cerebellum as the primary site. Because C71.6 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 C71.6 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Ensure documentation clearly identifies the cerebellum as the primary site
- •Note any documented symptoms like ataxia or balance problems, which are common with cerebellar tumors
Clinical Significance
Cerebellar malignancy affects balance, coordination, and fine motor control. In children, medulloblastoma is the most common posterior fossa tumor and requires aggressive treatment with surgery, craniospinal irradiation, and chemotherapy. In adults, cerebellar metastases are more common than primary tumors, making the distinction between primary and secondary disease critical for correct coding.
Documentation Requirements
- ✓Pathology confirming primary malignancy (medulloblastoma, astrocytoma, hemangioblastoma) with World Health Organization grade
- ✓MRI brain documenting cerebellar location and extent
- ✓Assessment for hydrocephalus (common with posterior fossa tumors obstructing the fourth ventricle)
- ✓Neurological examination documenting cerebellar signs (ataxia, dysmetria, nystagmus)
- ✓Molecular subtyping for medulloblastoma if applicable
Commonly Confused Codes
- •C71.7 — Brain stem: cerebellar and brain stem tumors are adjacent; confirm primary site from imaging
- •C71.5 — Cerebral ventricle: fourth ventricle tumors may extend into the cerebellum or vice versa
- •C71.8 — Overlapping sites: use when tumor extends from cerebellum into brain stem or other regions
- •C79.31 — Brain metastasis: cerebellar metastases (especially from lung, breast, colon) are far more common than primary cerebellar cancer in adults