D49.6
BillableNeoplasm of unspecified behavior of brain
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is D49.6 an HCC code?
Yes. D49.6 maps to Prostate, Breast, and Other Cancers and Tumors under the CMS-HCC V28 risk adjustment model (and Breast, Prostate, and Other Cancers and Tumors 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 D49.6
For D49.6to 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 D49.6 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
D49.6 is the ICD-10-CM diagnosis code for neoplasm of unspecified behavior of brain. A tumor or growth in the brain whose behavior (whether it will grow, spread, or cause harm) cannot be determined from the available information. D49.6 sits in the ICD-10-CM chapter for neoplasms (c00-d49), within the section covering neoplasms of unspecified behavior (d49).
Under the CMS-HCC V28 risk adjustment model, D49.6 maps to Prostate, Breast, and Other Cancers and Tumors (HCC 23) with a community, non-dual, aged base RAF weight of 0.186. Under the older CMS-HCC V24 model, D49.6 maps to Breast, Prostate, and Other Cancers and Tumors (HCC 12) with a community, non-dual, aged base RAF weight of 0.150. 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.
Use this code only when the pathology report explicitly states 'unspecified behavior' or when behavior cannot be determined. Because D49.6 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 D49.6 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Use this code only when the pathology report explicitly states 'unspecified behavior' or when behavior cannot be determined
- •If behavior is later determined to be benign or malignant, update the code to the appropriate D3x or C7x code
Clinical Significance
This code identifies brain neoplasms where the biological behavior cannot be determined from available pathologic or clinical data. These tumors may be awaiting definitive biopsy results or may have ambiguous histologic features that prevent classification as benign, malignant, or uncertain behavior. The clinical impact is significant because brain tumors of any behavior carry neurological risk and require monitoring or intervention.
Documentation Requirements
- ✓Documentation must include the anatomic location within the brain, imaging findings (Magnetic Resonance Imaging or Computed Tomography), reason why behavior cannot be determined (e.g., awaiting biopsy, inconclusive pathology), and current management plan.
- ✓If a biopsy or surgical specimen later clarifies behavior, the code should be updated to the appropriate benign (D33.x), uncertain (D43.x), or malignant (C71.x) category.
Excludes 1 — Do NOT code together
Commonly Confused Codes
- •D49.6 vs. D43.0-D43.2 (Neoplasm of uncertain behavior of brain) -
- •use D43 codes when pathology confirms uncertain behavior specifically. D49.6 vs. C71.x (Malignant neoplasm of brain) -
- •use C71 when malignancy is confirmed. D49.6 vs. D33.x (Benign neoplasm of brain) -
- •use D33 when benign behavior is confirmed on pathology.