C56.1
BillableMalignant neoplasm of right ovary
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is C56.1 an HCC code?
Yes. C56.1 maps to Colorectal, Bladder, and Other Cancers under the CMS-HCC V28 risk adjustment model (and Lymphoma 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 C56.1
For C56.1 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 C56.1 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
C56.1 is the ICD-10-CM diagnosis code for malignant neoplasm of right ovary. Cancer that starts in the right ovary, one of the two female reproductive glands that produce eggs and hormones. C56.1 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, C56.1 maps to Colorectal, Bladder, and Other Cancers (HCC 22) with a community, non-dual, aged base RAF weight of 0.000. Under the older CMS-HCC V24 model, C56.1 maps to Lymphoma and Other Cancers (HCC 10) with a community, non-dual, aged base RAF weight of 0.675. 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.
Confirm laterality is specifically documented as right; do not assume if bilateral involvement is possible. Because C56.1 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 C56.1 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Confirm laterality is specifically documented as right; do not assume if bilateral involvement is possible
- •Verify histology type (serous, mucinous, clear cell, etc.) for complete coding
Clinical Significance
Malignant neoplasm of the right ovary is a significant oncological diagnosis. Ovarian cancer is often called the 'silent killer' because it frequently presents at advanced stages due to nonspecific symptoms. It is the most lethal gynecological malignancy with a five-year survival rate that varies dramatically by stage — over 90% for stage I but under 30% for stage III/IV.
Documentation Requirements
- ✓Laterality confirmed as right ovary
- ✓Histological type (serous, mucinous, endometrioid, clear cell, transitional, undifferentiated)
- ✓Grade (low-grade vs. high-grade serous is a critical distinction)
- ✓FIGO staging
- ✓Peritoneal spread assessment
- ✓Lymph node status
- ✓CA-125 and other tumor marker levels
- ✓BRCA mutation status if tested
- ✓Debulking surgery status (optimal vs. suboptimal cytoreduction)