C66.9
BillableMalignant neoplasm of unspecified ureter
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is C66.9 an HCC code?
Yes. C66.9 maps to Colorectal, Bladder, and Other Cancers under the CMS-HCC V28 risk adjustment model (and Colorectal, Bladder, 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 C66.9
For C66.9to 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 C66.9 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
C66.9 is the ICD-10-CM diagnosis code for malignant neoplasm of unspecified ureter. Cancer of the ureter (the tube carrying urine from kidney to bladder) when the specific side is not documented or specified. C66.9 sits in the ICD-10-CM chapter for neoplasms (c00-d49), within the section covering malignant neoplasms of urinary tract (c64-c68).
Under the CMS-HCC V28 risk adjustment model, C66.9 maps to Colorectal, Bladder, and Other Cancers (HCC 22) with a community, non-dual, aged base RAF weight of 0.000. Under the older V24 model, C66.9 mapped to the same category but with a base RAF weight of 0.306 — V28 recalibrated weights across the entire model. 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 only when laterality cannot be determined from documentation. Because C66.9 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 C66.9 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Use only when laterality cannot be determined from documentation
- •Query provider if laterality information is available elsewhere in the record
Clinical Significance
Unspecified ureteral cancer should be used only when laterality cannot be determined. Since ureteral tumors are diagnosed by imaging (CT urogram), ureteroscopy, or surgical pathology — all of which specify laterality — this code should rarely be necessary. A provider query should always precede assignment of this unspecified code.
Documentation Requirements
- ✓Confirmation of ureteral malignancy
- ✓Evidence of query for laterality
- ✓Imaging or pathology documentation reviewed
- ✓Treatment status