C71.7
BillableMalignant neoplasm of brain stem
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is C71.7 an HCC code?
Yes. C71.7 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 C71.7
For C71.7 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 C71.7 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
C71.7 is the ICD-10-CM diagnosis code for malignant neoplasm of brain stem. Cancer that develops in the brain stem, the part of the brain that controls vital functions like breathing and heart rate. This is a malignant tumor in the lowest part of the brain. C71.7 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, C71.7 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, C71.7 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.
Brain stem tumors are particularly serious; ensure documentation reflects the critical location. Because C71.7 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 C71.7 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Brain stem tumors are particularly serious; ensure documentation reflects the critical location
- •Document any neurological deficits affecting vital functions or cranial nerves
Clinical Significance
Brain stem malignancy is among the most lethal of all brain cancers because the brain stem controls vital functions including breathing, heart rate, consciousness, and cranial nerve function. Diffuse intrinsic pontine glioma is the most devastating pediatric brain tumor with a median survival of less than one year. In adults, brain stem gliomas carry a similarly poor prognosis.
Documentation Requirements
- ✓Pathology or characteristic MRI findings sufficient for diagnosis (many brain stem tumors are diagnosed radiographically without biopsy due to surgical risk)
- ✓MRI brain documenting brain stem location (midbrain, pons, medulla)
- ✓Assessment of cranial nerve function and vital sign stability
- ✓Documentation of specific brain stem structure involved if known
- ✓Treatment plan (radiation, chemotherapy) — surgery is often not feasible