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C43.8 ICD-10-CM Code: Malignant melanoma of overlapping sites of skin

C43.8 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 · free HCC coding tools

ICD-10-CM Code View

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

Code lookupC43.8

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

C43.8

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

Malignant melanoma of overlapping sites of skin

A type of skin cancer (melanoma) that involves multiple overlapping areas of the skin rather than being confined to one specific location. This serious cancer requires prompt treatment.

Buddy the Bee presenting code insight

Buddy Insight

Malignant melanoma of overlapping sites of skin.

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 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 skinC43.8Malignant melanoma of overlapping sites of skin

Inclusion Terms

Official

No inclusion terms are included in this display for C43.8. 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
C43.0Malignant melanoma of lipC43.1Malignant melanoma of eyelid, including canthusC43.2Malignant melanoma of ear and external auricular canalC43.3Malignant melanoma of other and unspecified parts of faceC43.4Malignant melanoma of scalp and neck

Includes

Official

No Includes notes are included in this display for C43.8. 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 C43.8. Check the code and parent instructions in the Code Book.

Use Additional

Official

No Use Additional Code instructions are included in this display for C43.8. Check the code and parent instructions in the Code Book.

Code Also

Official

No Code Also instructions are included in this display for C43.8. Check the code and parent instructions in the Code Book.

Buddy Documentation Tip

HCC Buddy guidance
Documentation that the melanoma crosses anatomic site boundaries
Description of which overlapping sites are involved
Breslow depth and ulceration status
Sentinel lymph node biopsy results

MEAT Support

HCC Buddy guidance
Documentation that the melanoma crosses anatomic site boundaries
Description of which overlapping sites are involved
Breslow depth and ulceration status
Sentinel lymph node biopsy results

Audit Caution

HCC Buddy guidance
Using overlapping sites code when the melanoma can be assigned to a single primary site — most melanomas have an identifiable primary site
Confusing overlapping sites (one continuous lesion crossing anatomic boundaries) with multiple primary melanomas (separate lesions)
Using this code for satellite lesions or in-transit metastases, which indicate metastatic disease
Not attempting to identify the single most representative anatomic site before resorting to the overlapping code

Common Mistakes

HCC Buddy guidance
C43.9 — Melanoma of skin, unspecified; for when the site is unknown, not overlapping
C43.59 — Melanoma of other parts of trunk; if the melanoma is primarily on the trunk with extension to an adjacent site
C79.2 — Secondary malignant neoplasm of skin; for melanoma metastases to skin (satellite lesions or in-transit metastases)
Site-specific melanoma codes (C43.0-C43.72) — always preferred when a primary site can be identified

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 C43.8 an HCC code?

Yes. C43.8 (Malignant melanoma of overlapping sites of skin) 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: C43.8 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
C43.8
Description
Malignant melanoma of overlapping sites of skin
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 C43.8 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →

MEAT review for C43.8

For C43.8, 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

C43.8 is the ICD-10-CM diagnosis code for malignant melanoma of overlapping sites of skin. A type of skin cancer (melanoma) that involves multiple overlapping areas of the skin rather than being confined to one specific location. This serious cancer requires prompt treatment. C43.8 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, C43.8 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 C43.8; 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.

Use this code when melanoma involves two or more contiguous or overlapping skin sites. For C43.8, 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 C43.8 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

  • •Use this code when melanoma involves two or more contiguous or overlapping skin sites
  • •Document all involved anatomical sites in the medical record for comprehensive treatment planning

Clinical Significance

Malignant melanoma of overlapping sites of skin. This code is used when a single melanoma extends across two or more contiguous skin anatomic sites and the primary site cannot be determined, or when the melanoma equally involves multiple sites. This is uncommon and most melanomas can be assigned to a single primary site.

Documentation Requirements

  • ✓Documentation that the melanoma crosses anatomic site boundaries
  • ✓Description of which overlapping sites are involved
  • ✓Breslow depth and ulceration status
  • ✓Sentinel lymph node biopsy results
  • ✓AJCC staging
  • ✓Reason a single primary site cannot be identified

Commonly Confused Codes

  • •C43.9: Melanoma of skin, unspecified; for when the site is unknown, not overlapping
  • •C43.59: Melanoma of other parts of trunk; if the melanoma is primarily on the trunk with extension to an adjacent site
  • •C79.2: Secondary malignant neoplasm of skin; for melanoma metastases to skin (satellite lesions or in-transit metastases)
  • •Site-specific melanoma codes (C43.0-C43.72): always preferred when a primary site can be identified

Child Codes

C43.0Malignant melanoma of lip
HCC 23
C43.1Malignant melanoma of eyelid, including canthus
C43.2Malignant melanoma of ear and external auricular canal
C43.3Malignant melanoma of other and unspecified parts of face
C43.4Malignant melanoma of scalp and neck
HCC 23
C43.5Malignant melanoma of trunk
C43.6Malignant melanoma of upper limb, including shoulder
C43.7Malignant melanoma of lower limb, including hip
C43.8Malignant melanoma of overlapping sites of skin
HCC 23
C43.9Malignant melanoma of skin, unspecified
HCC 23

Code Hierarchy

└C43Malignant melanoma of skin└C43.8Malignant melanoma of overlapping sites of skin
└C43.8Malignant melanoma of overlapping sites of skin

Also searched as

  • C43 8
  • C438

For C43.8, 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.

C43.8 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 C43.8. 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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