C54.0
BillableMalignant neoplasm of isthmus uteri
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is C54.0 an HCC code?
Yes. C54.0 maps to Melanoma and Other Skin Cancers 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 C54.0
For C54.0 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 C54.0 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
C54.0 is the ICD-10-CM diagnosis code for malignant neoplasm of isthmus uteri. Cancer that starts in the isthmus uteri, the narrow lower portion of the uterus that connects to the cervix. C54.0 sits in the ICD-10-CM chapter for neoplasms (c00-d49), within the section covering malignant neoplasms of female genital organs (c51-c58).
Under the CMS-HCC V28 risk adjustment model, C54.0 maps to Melanoma and Other Skin Cancers (HCC 23) with a community, non-dual, aged base RAF weight of 0.251. Under the older CMS-HCC V24 model, C54.0 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.
Adenocarcinoma is the most common histological type for uterine cancers; document when present. Because C54.0 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 C54.0 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Adenocarcinoma is the most common histological type for uterine cancers; document when present
- •Verify whether the tumor is confined to the isthmus or extends into the corpus or cervix for staging purposes
Clinical Significance
Malignant neoplasm of the isthmus uteri involves the narrow transitional zone between the uterine corpus and the cervix. This location is clinically significant because tumors here may have features of both endometrial and endocervical cancers, complicating both staging and treatment planning. The isthmus is sometimes referred to as the lower uterine segment.
Documentation Requirements
- ✓Specific site confirmed as isthmus uteri (lower uterine segment)
- ✓Histological type and grade
- ✓FIGO staging for uterine cancer
- ✓Depth of myometrial invasion
- ✓Cervical involvement assessment (determines stage II vs. stage I)
- ✓Lymph node status
- ✓Lymphovascular space invasion documentation