C64.1
BillableMalignant neoplasm of right kidney, except renal pelvis
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is C64.1 an HCC code?
Yes. C64.1 maps to Bladder, Colorectal, 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 C64.1
For C64.1to 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 C64.1 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
C64.1 is the ICD-10-CM diagnosis code for malignant neoplasm of right kidney, except renal pelvis. Cancer that develops in the right kidney, excluding the renal pelvis (the funnel-shaped structure that collects urine). C64.1 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, C64.1 maps to Bladder, Colorectal, and Other Cancers (HCC 22) with a community, non-dual, aged base RAF weight of 0.363. Under the older CMS-HCC V24 model, C64.1 maps to Colorectal, Bladder, and Other Cancers (HCC 11) with a community, non-dual, aged base RAF weight of 0.307. 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 laterality is documented as 'right' to distinguish from C64.2. Because C64.1 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 C64.1 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
Clinical Significance
Right kidney cancer (excluding renal pelvis) most commonly represents renal cell carcinoma, which accounts for approximately 90% of kidney cancers. Distinguishing kidney parenchymal cancer from renal pelvis cancer is critical because they have different histologic types, treatment approaches, and ICD-10 code assignments. Laterality documentation is essential for surgical planning (nephrectomy type) and renal function preservation.
Documentation Requirements
- ✓Pathology confirming malignancy of the right kidney parenchyma (not renal pelvis)
- ✓Histologic type (clear cell, papillary, chromophobe renal cell carcinoma)
- ✓Fuhrman nuclear grade
- ✓TNM staging with tumor size
- ✓Imaging confirming right-sided location
- ✓Renal function assessment and contralateral kidney status
- ✓Treatment plan (radical vs. partial nephrectomy, targeted therapy)
Commonly Confused Codes
- •C65.1 — Right renal pelvis cancer; kidney parenchyma (C64.1) and renal pelvis (C65.1) are different anatomical locations with different histologies
- •C64.2 — Left kidney cancer; verify laterality
- •C64.9 — Unspecified kidney; always prefer C64.1 when right is documented
- •D41.01 — Neoplasm of uncertain behavior of right kidney; use when histology is indeterminate
- •C79.01 — Secondary malignant neoplasm of right kidney; distinguish primary from metastatic