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C43.10 ICD-10-CM Code: Malignant melanoma of unspecified eyelid, including canthus

C43.10 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 coding software

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Code lookupC43.10

FY 2026 Apr update / Neoplasms (C00-D49) / Melanoma and other malignant neoplasms of skin (C43-C44)

C43.10

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

Malignant melanoma of unspecified eyelid, including canthus

Melanoma (a serious type of skin cancer) of the eyelid when the specific eye is not identified.

Buddy the Bee presenting code insight

Buddy Insight

Malignant melanoma of the eyelid, including the canthus, with unspecified laterality.

OverviewRisk ModelsCode BookDocumentationAuditNotesEdition comparison

CMS-HCC V28

HCC 23

Code-level coefficient reference

CMS-HCC V24

Historical

Historical

Not used for CY2026 payment

ACA/HHS

HCC 013

Code-level coefficient reference

ESRD/PACE

HCC 12

Code-level coefficient reference

RXHCC

HCC 22

Code-level coefficient reference

Code Book Path

Official
C43Malignant melanoma of skinC43.1Malignant melanoma of eyelid, including canthusC43.10Malignant melanoma of unspecified eyelid, including canthus

Inclusion Terms

Official

No inclusion terms are included in this display for C43.10. Check the code and parent instructions in the Code Book.

Excludes 2

Official
  • malignant melanoma of skin of genital organs (C51-C52, C60.-, C63.-)Inherited from C43
  • Merkel cell carcinoma (C4A.-)Inherited from C43
  • sites other than skin-code to malignant neoplasm of the siteInherited from C43

Related Codes

Official
C43.11Malignant melanoma of right eyelid, including canthusC43.12Malignant melanoma of left eyelid, including canthus

Includes

Official

No Includes notes are included in this display for C43.10. Check the code and parent instructions in the Code Book.

Excludes 1

Official
  • melanoma in situ (D03.-)Inherited from C43

Code First

Official

No Code First sequencing instructions are included in this display for C43.10. Check the code and parent instructions in the Code Book.

Use Additional

Official

No Use Additional Code instructions are included in this display for C43.10. Check the code and parent instructions in the Code Book.

Code Also

Official

No Code Also instructions are included in this display for C43.10. Check the code and parent instructions in the Code Book.

Buddy Documentation Tip

HCC Buddy guidance
Attempt to clarify laterality (right vs. left) and specific eyelid (upper vs. lower)
Breslow depth and Clark level
Whether the canthus (inner or outer corner) is involved
Ulceration status and mitotic rate

MEAT Support

HCC Buddy guidance
Attempt to clarify laterality (right vs. left) and specific eyelid (upper vs. lower)
Breslow depth and Clark level
Whether the canthus (inner or outer corner) is involved
Ulceration status and mitotic rate

Audit Caution

HCC Buddy guidance
Using unspecified laterality when the record documents which eye is affected
Confusing eyelid melanoma with conjunctival melanoma (C69.0) or uveal melanoma (C69.3/C69.4) — these are different sites with different prognoses
Coding melanoma in situ of the eyelid as invasive melanoma
Not specifying upper vs. lower eyelid when the documentation supports it

Common Mistakes

HCC Buddy guidance
C43.111/C43.112 — Melanoma of right upper/lower eyelid; use when right side is documented
C43.121/C43.122 — Melanoma of left upper/lower eyelid; use when left side is documented
C44.10x — Other skin cancer of eyelid (basal cell or squamous cell carcinoma); different histology
D03.10 — Melanoma in situ of unspecified eyelid; non-invasive, does not map to HCC

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 C43.10 an HCC code?

Yes. C43.10 (Malignant melanoma of unspecified eyelid, including canthus) 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: C43.10 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
C43.10
Description
Malignant melanoma of unspecified eyelid, including canthus
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
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 C43.10 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →

MEAT review for C43.10

For C43.10, 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

C43.10 is the ICD-10-CM diagnosis code for malignant melanoma of unspecified eyelid, including canthus. Melanoma (a serious type of skin cancer) of the eyelid when the specific eye is not identified. C43.10 sits in the ICD-10-CM chapter for neoplasms (c00-d49), within the section covering melanoma and other malignant neoplasms of skin (c43-c44).

Under the CMS-HCC V28 risk adjustment model, C43.10 maps to Prostate, Breast, and Other Cancers and Tumors (HCC 23) with a source-labeled community, non-dual, aged reference coefficient of 0.186. No V24 mapping is shown for C43.10; 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.

Eyelid melanoma is relatively rare; ensure documentation clearly indicates eyelid location. For C43.10, 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 C43.10 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

  • •Eyelid melanoma is relatively rare; ensure documentation clearly indicates eyelid location
  • •Query for laterality (right or left eye) to assign a more specific code if available

Clinical Significance

Malignant melanoma of the eyelid, including the canthus, with unspecified laterality. Eyelid melanomas are rare but important because of their proximity to the eye and potential for orbital and intracranial spread. Mohs micrographic surgery or wide excision with margin control is typically required. The unspecified laterality should prompt a provider query.

Documentation Requirements

  • ✓Attempt to clarify laterality (right vs. left) and specific eyelid (upper vs. lower)
  • ✓Breslow depth and Clark level
  • ✓Whether the canthus (inner or outer corner) is involved
  • ✓Ulceration status and mitotic rate
  • ✓Sentinel lymph node biopsy results (parotid and cervical nodes)
  • ✓AJCC staging

Commonly Confused Codes

  • •C43.111/C43.112: Melanoma of right upper/lower eyelid; use when right side is documented
  • •C43.121/C43.122: Melanoma of left upper/lower eyelid; use when left side is documented
  • •C44.10x: Other skin cancer of eyelid (basal cell or squamous cell carcinoma); different histology
  • •D03.10: Melanoma in situ of unspecified eyelid; non-invasive, does not map to HCC

Child Codes

C43.10Malignant melanoma of unspecified eyelid, including canthus
HCC 23
C43.11Malignant melanoma of right eyelid, including canthus
C43.12Malignant melanoma of left eyelid, including canthus

Code Hierarchy

└C43Malignant melanoma of skin└C43.1Malignant melanoma of eyelid, including canthus└C43.10Malignant melanoma of unspecified eyelid, including canthus
└C43.10Malignant melanoma of unspecified eyelid, including canthus

For C43.10, 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.

C43.10 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 C43.10. 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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