C55
BillableMalignant neoplasm of uterus, part unspecified
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is C55 an HCC code?
Yes. C55 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 C55
For C55to 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 C55 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
C55 is the ICD-10-CM diagnosis code for malignant neoplasm of uterus, part unspecified. This code represents cancer of the uterus (womb) when the specific part affected is not documented or specified. The uterus is the female reproductive organ where a fetus develops during pregnancy. C55 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, C55 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, C55 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 medical record does not specify which part of the uterus is affected (such as the corpus, fundus, or isthmus); if the location is documented, use a more specific C54.x code instead. Because C55 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 C55 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 medical record does not specify which part of the uterus is affected (such as the corpus, fundus, or isthmus); if the location is documented, use a more specific C54.x code instead
- •Verify documentation for staging information (TNM stage) and histological type, as these details are often required for cancer reporting and treatment planning
Clinical Significance
Malignant neoplasm of uterus, part unspecified, is the broadest uterine cancer code encompassing both cervical and corpus malignancies when the specific part cannot be determined. This code should be extremely rare in practice because diagnostic workup for uterine cancer virtually always identifies whether the cervix or corpus is the primary site.
Documentation Requirements
- ✓Confirmed uterine malignancy
- ✓Documentation explaining why the specific uterine part (cervix vs. corpus) cannot be determined
- ✓Histological type if available
- ✓Staging information
- ✓Evidence of comprehensive record review
- ✓Provider query documentation for part specification
Commonly Confused Codes
- •C54.9 — Corpus uteri, unspecified; more specific — identifies the cancer is in the uterine body
- •C53.9 — Cervix uteri, unspecified; more specific — identifies the cancer is in the cervix
- •C54.1 — Endometrium; the most specific and common uterine cancer code
- •Z85.42 — Personal history of uterine cancer; use only when no active disease remains