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C56.9 ICD-10-CM Code: Malignant neoplasm of unspecified ovary

C56.9 maps to CMS-HCC V28 22. A source-labeled RAF reference is available. Confirm the documented diagnosis and applicable coding requirements. MEAT criteria · RAF Calculator · HCC coding software

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Code lookupC56.9

FY 2026 Apr update / Neoplasms (C00-D49) / Malignant neoplasms of female genital organs (C51-C58)

C56.9

Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidance

Malignant neoplasm of unspecified ovary

Cancer of the ovary where the specific side (left, right, or bilateral) has not been specified or documented.

Buddy the Bee presenting code insight

Buddy Insight

Malignant neoplasm of unspecified ovary lacks laterality documentation, which is a significant gap for a diagnosis that requires surgical planning and cancer registry reporting.

OverviewRisk ModelsCode BookDocumentationAuditNotesEdition comparison

CMS-HCC V28

HCC 22

Coefficient HCC 22: 0.363 (Community Non-Dual Aged (CNA))

CMS-HCC V24

Historical

Historical

Not used for CY2026 payment

ACA/HHS

HCC 011

Code-level coefficient reference

ESRD/PACE

HCC 10

Code-level coefficient reference

RXHCC

HCC 22

Code-level coefficient reference

Code Book Path

Official
C56Malignant neoplasm of ovaryC56.9Malignant neoplasm of unspecified ovary

Inclusion Terms

Official

No inclusion terms are included in this display for C56.9. Check the code and parent instructions in the Code Book.

Excludes 2

Official

No Excludes 2 notes are included in this display for C56.9. Check the code and parent instructions in the Code Book.

Related Codes

Official
C56.1Malignant neoplasm of right ovaryC56.2Malignant neoplasm of left ovaryC56.3Malignant neoplasm of bilateral ovaries

Includes

Official
  • malignant neoplasm of skin of female genital organsInherited from C51-C58

Excludes 1

Official

No Excludes 1 notes are included in this display for C56.9. Check the code and parent instructions in the Code Book.

Code First

Official

No Code First sequencing instructions are included in this display for C56.9. Check the code and parent instructions in the Code Book.

Use Additional

Official
  • code to identify any functional activityInherited from C56

Code Also

Official

No Code Also instructions are included in this display for C56.9. Check the code and parent instructions in the Code Book.

Buddy Documentation Tip

HCC Buddy guidance
Confirmed ovarian malignancy
Documentation explaining why laterality cannot be determined
Evidence of record review for laterality information (imaging, surgical reports, pathology)
Histological type and grade

MEAT Support

HCC Buddy guidance
Confirmed ovarian malignancy
Documentation explaining why laterality cannot be determined
Evidence of record review for laterality information (imaging, surgical reports, pathology)
Histological type and grade

Audit Caution

HCC Buddy guidance
Using this code when laterality is available in imaging, surgical, or pathology reports
Not querying the provider for laterality specification
Confusing neoplasm of uncertain behavior with confirmed malignancy
This code should trigger a documentation improvement initiative if used frequently

Common Mistakes

HCC Buddy guidance
C56.1 — Right ovary; use when right laterality is confirmed
C56.2 — Left ovary; use when left laterality is confirmed
C56.3 — Bilateral ovaries; use when both ovaries are involved
D39.10 — Neoplasm of uncertain behavior of unspecified ovary; different from confirmed malignancy

Current with CMS: FY2026 ICD-10-CM Apr 1 update (effective Apr 1 – Sep 30, 2026) · CMS-HCC V28, 100% phased in for payment year 2026. FY2027 code set already staged for October 1, 2026. How HCC Buddy stays current →

Is C56.9 an HCC code?

Yes. C56.9 (Malignant neoplasm of unspecified ovary) maps to HCC 22, Bladder, Colorectal, and Other Cancers under the CMS-HCC V28 risk adjustment model, with a source-labeled community non-dual aged reference coefficient of 0.363. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes. It is billable for payment year 2026.

Coder answer: C56.9 is billable and maps to V28 HCC 22, Bladder, Colorectal, and Other Cancers. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.

Code
C56.9
Description
Malignant neoplasm of unspecified ovary
HCC (V28)
HCC 22 — Bladder, Colorectal, and Other Cancers
RAF reference coefficient
0.363
Billable
Yes
Payment year
2026

HCC Category Mapping

V28HCC 22, Bladder, Colorectal, and Other Cancers
0.363
ESRDHCC 10, Lymphoma and Other Cancers
Not separately weighted
RxHCCHCC 22, Prostate, Breast, Bladder, and Other Cancers and Tumors
Not separately weighted

These are source-labeled model coefficients, not member totals. A category may still be removed by hierarchy or model cleanup rules. Weights are not directly comparable across models: CMS-HCC V28 and V24 use Community, Non-Dual, Aged; ESRD uses the dialysis continuing-enrollee model; RxHCC is the Part D continuing-enrollee, non-low-income, aged weight (a larger scale than CMS-HCC). ACA/HHS has no single weight — it varies by metal level. Actual per-patient RAF contribution depends on member context, hierarchy and cleanup rules, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains available for historical review.

Work C56.9 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →

MEAT review for C56.9

For C56.9, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule.

  • 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

Coder workflow notes

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What This Code Means

C56.9 is the ICD-10-CM diagnosis code for malignant neoplasm of unspecified ovary. Cancer of the ovary where the specific side (left, right, or bilateral) has not been specified or documented. C56.9 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, C56.9 maps to Bladder, Colorectal, and Other Cancers (HCC 22) with a source-labeled community, non-dual, aged reference coefficient of 0.363. No V24 mapping is shown for C56.9; use the applicable model and payment year when reviewing the V28 mapping. For CY2026 non-PACE Medicare Advantage, CMS uses 100% of the 2024 CMS-HCC model (V28). PACE uses a separate model blend. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes.

Query the provider for laterality information when possible, as C56.1, C56.2, or C56.3 are more specific. For C56.9, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule. 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, source-labeled coefficient references, and MEAT documentation criteria for C56.9 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

  • •Query the provider for laterality information when possible, as C56.1, C56.2, or C56.3 are more specific
  • •Use only when laterality cannot be determined from available documentation

Clinical Significance

Malignant neoplasm of unspecified ovary lacks laterality documentation, which is a significant gap for a diagnosis that requires surgical planning and cancer registry reporting. Given that ovarian cancer diagnosis almost always involves imaging or surgery that identifies the affected side, this code should be used only in exceptional circumstances.

Documentation Requirements

  • ✓Confirmed ovarian malignancy
  • ✓Documentation explaining why laterality cannot be determined
  • ✓Evidence of record review for laterality information (imaging, surgical reports, pathology)
  • ✓Histological type and grade
  • ✓Staging information
  • ✓Provider query documentation for laterality

Commonly Confused Codes

  • •C56.1: Right ovary; use when right laterality is confirmed
  • •C56.2: Left ovary; use when left laterality is confirmed
  • •C56.3: Bilateral ovaries; use when both ovaries are involved
  • •D39.10: Neoplasm of uncertain behavior of unspecified ovary; different from confirmed malignancy

Child Codes

C56.1Malignant neoplasm of right ovary
HCC 22
C56.2Malignant neoplasm of left ovary
HCC 22
C56.3Malignant neoplasm of bilateral ovaries
HCC 22
C56.9Malignant neoplasm of unspecified ovary
HCC 22

Code Hierarchy

└C56Malignant neoplasm of ovary└C56.9Malignant neoplasm of unspecified ovary
└C56.9Malignant neoplasm of unspecified ovary

Also searched as

  • C56 9
  • C569

For C56.9, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule.

C56.9 maps to CMS-HCC V28 category 22, Bladder, Colorectal, and Other Cancers. See the ICD-10 to HCC mapping hub for how the V28 crosswalk works. The mapping identifies a payment HCC category for C56.9. Review its source-labeled HCC coefficient above, check the RAF Calculator with complete member context for CMS-HCC V28 PY2026, and confirm the documentation the chart needs before the code is submitted. HCC Buddy shows no RAF score unless every required source and calculation check passes.

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