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C55 ICD-10-CM Code: Malignant neoplasm of uterus, part unspecified

C55 maps to CMS-HCC V28 23. A source-labeled RAF reference is available. Confirm the documented diagnosis and applicable coding requirements. MEAT criteria · RAF Calculator · HCC Buddy coding tools

ICD-10-CM Code View

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Code lookupC55

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

C55

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

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.

Buddy the Bee presenting code insight

Buddy Insight

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.

OverviewRisk ModelsCode BookDocumentationAuditNotesEdition comparison

CMS-HCC V28

HCC 23

Coefficient HCC 23: 0.186 (Community Non-Dual Aged (CNA))

CMS-HCC V24

Historical

Historical

Not used for CY2026 payment

ACA/HHS

HCC 012

Code-level coefficient reference

ESRD/PACE

HCC 12

Code-level coefficient reference

RXHCC

N/A

—

Not mapped

Code Book Path

Official
C5Malignant neoplasms of female genital organs (C51-C58)C55Malignant neoplasm of uterus, part unspecified

Inclusion Terms

Official

No inclusion terms are included in this display for C55. Check the code and parent instructions in the Code Book.

Excludes 2

Official

No Excludes 2 notes are included in this display for C55. Check the code and parent instructions in the Code Book.

Related Codes

Official

No related codes are included in this display for C55. Check the Code Book for the complete code path.

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 C55. Check the code and parent instructions in the Code Book.

Code First

Official

No Code First sequencing instructions are included in this display for C55. Check the code and parent instructions in the Code Book.

Use Additional

Official

No Use Additional Code instructions are included in this display for C55. Check the code and parent instructions in the Code Book.

Code Also

Official

No Code Also instructions are included in this display for C55. Check the code and parent instructions in the Code Book.

Buddy Documentation Tip

HCC Buddy guidance
Confirmed uterine malignancy
Documentation explaining why the specific uterine part (cervix vs. corpus) cannot be determined
Histological type if available
Staging information

MEAT Support

HCC Buddy guidance
Confirmed uterine malignancy
Documentation explaining why the specific uterine part (cervix vs. corpus) cannot be determined
Histological type if available
Staging information

Audit Caution

HCC Buddy guidance
Using this code when the cervix or corpus is identifiable from biopsy, imaging, or pathology reports
This is a coding quality indicator — high usage rates suggest systematic documentation review issues
Not distinguishing between cervical cancer and endometrial cancer, which have fundamentally different staging and treatment
Failing to query the provider when the specific uterine part is not documented in the encounter note but available in referenced reports

Common Mistakes

HCC Buddy guidance
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

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 C55 an HCC code?

Yes. C55 (Malignant neoplasm of uterus, part unspecified) maps to HCC 23, Prostate, Breast, and Other Cancers and Tumors under the CMS-HCC V28 risk adjustment model, with a source-labeled community non-dual aged reference coefficient of 0.186. 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: C55 is billable and maps to V28 HCC 23, Prostate, Breast, and Other Cancers and Tumors. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.

Code
C55
Description
Malignant neoplasm of uterus, part unspecified
HCC (V28)
HCC 23 — Prostate, Breast, and Other Cancers and Tumors
RAF reference coefficient
0.186
Billable
Yes
Payment year
2026

HCC Category Mapping

V28HCC 23, Prostate, Breast, and Other Cancers and Tumors
0.186
ESRDHCC 12, Breast/Prostate/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 C55 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →

MEAT review for C55

For C55, 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

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 Prostate, Breast, and Other Cancers and Tumors (HCC 23) with a source-labeled community, non-dual, aged reference coefficient of 0.186. 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.

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. For C55, 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 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

Code Hierarchy

└C55Malignant neoplasm of uterus, part unspecified
└C55Malignant neoplasm of uterus, part unspecified

For C55, 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.

C55 maps to CMS-HCC V28 category 23, Prostate, Breast, and Other Cancers and Tumors. See the ICD-10 to HCC mapping hub for how the V28 crosswalk works. The mapping identifies a payment HCC category for C55. 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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