Skip to content
HCC Buddy home

C54.0 ICD-10-CM Code: Malignant neoplasm of isthmus uteri

C54.0 maps to CMS-HCC V28 23 (RAF 0.186). Documentation must support MEAT. MEAT criteria · RAF calculator · free HCC coding tools

ICD-10-CM Code View

HCC Buddy Code Card

Digital ICD-10 code-book layout with official code detail, always-visible risk models, Code Trumping, and Buddy coding guidance.

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

C54.0

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

Malignant neoplasm of isthmus uteri

Cancer that starts in the isthmus uteri, the narrow lower portion of the uterus that connects to the cervix.

Buddy the Bee presenting code insight

Buddy Insight

Malignant neoplasm of the isthmus uteri involves the narrow transitional zone between the uterine corpus and the cervix.

CMS-HCC V28

HCC 23

RAF 0.186

CMS-HCC V24

HCC 12

RAF 0.150

ACA/HHS

HCC 12

Varies by metal level

ESRD/PACE

HCC 12

RAF 0.045

RXHCC

N/A

—

Not mapped

Code Book Path

Official
C54Malignant neoplasm of corpus uteri
C54.0Malignant neoplasm of isthmus uteri

Inclusion Terms

Official
  • Malignant neoplasm of lower uterine segment

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for C54.0 in this effective period.

Related Child Codes

Official
C54.1Malignant neoplasm of endometrium
C54.2Malignant neoplasm of myometrium
C54.3Malignant neoplasm of fundus uteri
C54.8Malignant neoplasm of overlapping sites of corpus uteri
C54.9Malignant neoplasm of corpus uteri, unspecified

Includes

Official

ICD-10-CM does not list Includes notes for C54.0 in this effective period.

Excludes 1

Official

ICD-10-CM does not list Excludes 1 notes for C54.0 in this effective period.

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for C54.0 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for C54.0 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for C54.0 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance
Specific site confirmed as isthmus uteri (lower uterine segment)
Histological type and grade
FIGO staging for uterine cancer
Depth of myometrial invasion

MEAT Support

HCC Buddy guidance
Specific site confirmed as isthmus uteri (lower uterine segment)
Histological type and grade
FIGO staging for uterine cancer
Depth of myometrial invasion

Audit Caution

HCC Buddy guidance
Confusing isthmus uteri with endocervix — the isthmus is the uterine side of the cervico-uterine junction
Coding a cervical cancer extending to the lower uterine segment as isthmus primary when the cervix is the true primary site
Using the unspecified corpus uteri code when isthmus is specifically documented
Not recognizing 'lower uterine segment' as synonymous with isthmus uteri in some documentation

Common Mistakes

HCC Buddy guidance
C53.0 — Endocervix; isthmus tumors may extend into the endocervix — determine the primary site
C54.1 — Endometrium; isthmus is the junction between corpus and cervix, distinct from the endometrial cavity
C54.9 — Corpus uteri, unspecified; less specific when isthmus is identified
C55 — Uterus, part unspecified; even less specific

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 C54.0 an HCC code?

Yes. C54.0 (Malignant neoplasm of isthmus uteri) maps to Prostate, Breast, and Other Cancers and Tumors under the CMS-HCC V28 risk adjustment model (and Breast, Prostate, and Other Cancers and Tumors under V24), with a community non-dual aged RAF of 0.186. It is billable for payment year 2026.

Coder answer: C54.0 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
C54.0
Description
Malignant neoplasm of isthmus uteri
HCC (V28)
HCC 23 — Prostate, Breast, and Other Cancers and Tumors
RAF
0.186
Billable
Yes
Payment year
2026

HCC Category Mapping

V28HCC 23, Prostate, Breast, and Other Cancers and Tumors
0.186
V24HCC 12, Breast, Prostate, and Other Cancers and Tumors
0.150
ESRDHCC 12, Breast, Prostate, and Other Cancers and Tumors
0.045

Each model's RAF is its CMS base weight for that model's standard population, so 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 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.

Work C54.0 in the Code Book — tabular path, V28 RAF, and MEAT checklist →

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.

Coder workflow notes

Get the V28 RAF + MEAT cheat sheet

One printable page: confirm a code's V28 HCC status, its RAF weight, and the MEAT your note needs to make it stick. Free, no card.

Free PDF. No card. Unsubscribe anytime.

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 Prostate, Breast, and Other Cancers and Tumors (HCC 23) with a community, non-dual, aged base RAF weight of 0.186. 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

Commonly Confused Codes

  • •C53.0: Endocervix; isthmus tumors may extend into the endocervix: determine the primary site
  • •C54.1: Endometrium; isthmus is the junction between corpus and cervix, distinct from the endometrial cavity
  • •C54.9: Corpus uteri, unspecified; less specific when isthmus is identified
  • •C55: Uterus, part unspecified; even less specific

Child Codes

C54.0Malignant neoplasm of isthmus uteri
HCC 23
C54.1Malignant neoplasm of endometrium
HCC 23
C54.2Malignant neoplasm of myometrium
HCC 23
C54.3Malignant neoplasm of fundus uteri
HCC 23
C54.8Malignant neoplasm of overlapping sites of corpus uteri
HCC 23
C54.9Malignant neoplasm of corpus uteri, unspecified
HCC 23

Code Hierarchy

└C54Malignant neoplasm of corpus uteri└C54.0Malignant neoplasm of isthmus uteri
└C54.0Malignant neoplasm of isthmus uteri

Because C54.0 maps to a payment HCC, the documentation must also satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's risk adjustment score.

C54.0 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. Because C54.0 carries a payment HCC, you can see what it adds to a RAF score and check the documentation the chart needs before it is submitted.

Work C54.0 in HCC Buddy

Open C54.0 in the Code Book for the full Index-to-Tabular path, MEAT checklist, and V28 HCC mapping, or in the Encoder to code from a keyword search. Pro includes 7 days to try everything, no card required.

Open in Code BookOpen in EncoderStart Pro