What is ICD-10 code C4A.60?

C4A.60 is the ICD-10-CM diagnosis code for Merkel cell carcinoma of unspecified upper limb, including shoulder. It belongs to the ICD-10-CM chapter for neoplasms (c00-d49). C4A.60 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. C4A.60 is part of the FY2026 ICD-10-CM code set published by the CMS National Center for Health Statistics and used on Medicare, Medicaid, and commercial claims in the United States.

Yes. C4A.60 is a billable ICD-10-CM code that can be reported on professional and institutional claims as a primary or secondary diagnosis when the provider documentation supports the specific condition described. Billable codes in ICD-10-CM are coded to the highest level of specificity available for the documented diagnosis. C4A.60 is current for fiscal year 2026 and remains in the active CMS ICD-10-CM code set published by the National Center for Health Statistics.

Which HCC does C4A.60 map to under V28?

C4A.60 maps to CMS-HCC V28 HCC 21 (Lymphoma and Other Cancers). The category numbers, labels, and conditions come from the CMS-HCC V28 model file for payment year 2026.

2026 ICD-10-CM C4A.60: Merkel cell carcinoma

C4A.60 maps to CMS-HCC V28 21. 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 lookupC4A.60

Effective periodFY2026 Apr Update (Apr 1-Sep 30)

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

C4A.60

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

Merkel cell carcinoma of unspecified upper limb, including shoulder

Merkel cell carcinoma is a rare, aggressive skin cancer that develops from neuroendocrine cells in the skin. This code specifically identifies the cancer when it occurs somewhere on the upper arm, forearm, hand, or shoulder area, but the exact location on the upper limb is not specified.

Buddy Insight

Merkel cell carcinoma of the unspecified upper limb, including shoulder is a rare aggressive neuroendocrine skin cancer.

Overview Risk Models Code Book Documentation Audit Notes Edition comparison

CMS-HCC V28

Mapped

HCC 21

Lymphoma and Other Cancers

Code-level coefficient reference

CMS-HCC V24

Historical

Not used for standard CY2026 Medicare Advantage payment. Select a historical period to review V24.

Not used for CY2026 payment

ACA/HHS

Mapped

HCC 012

HHS-HCC 012 adult, RAF varies...

Code-level coefficient reference

ESRD/PACE

Mapped

HCC 12

Breast/Prostate/and Other Can...

Code-level coefficient reference

RXHCC

Mapped

HCC 22

Prostate, Breast, Bladder, an...

Code-level coefficient reference

Code Book Path

Official

C4AMerkel cell carcinoma C4A.6Merkel cell carcinoma of upper limb, including shoulder C4A.60Merkel cell carcinoma of unspecified upper limb, including shoulder

Inclusion Terms

Official

No inclusion terms are included in this display for C4A.60. Check the code and parent instructions in the Code Book.

Excludes 2

Official

No Excludes 2 notes are included in this display for C4A.60. Check the code and parent instructions in the Code Book.

Related Codes

Official

C4A.61Merkel cell carcinoma of right upper limb, including shoulder C4A.62Merkel cell carcinoma of left upper limb, including shoulder

Includes

Official

No Includes notes are included in this display for C4A.60. Check the code and parent instructions in the Code Book.

Excludes 1

Official

No Excludes 1 notes are included in this display for C4A.60. Check the code and parent instructions in the Code Book.

Code First

Official

No Code First sequencing instructions are included in this display for C4A.60. Check the code and parent instructions in the Code Book.

Use Additional

Official

No Use Additional Code instructions are included in this display for C4A.60. Check the code and parent instructions in the Code Book.

Code Also

Official

No Code Also instructions are included in this display for C4A.60. Check the code and parent instructions in the Code Book.

Buddy Documentation Tip

HCC Buddy guidance

Histopathologic confirmation of Merkel cell carcinoma with immunohistochemistry

Laterality must be queried — right or left upper limb

Specific upper limb subsite (shoulder, upper arm, forearm, wrist, hand, fingers)

Tumor dimensions and depth

MEAT Support

HCC Buddy guidance

Histopathologic confirmation of Merkel cell carcinoma with immunohistochemistry

Laterality must be queried — right or left upper limb

Specific upper limb subsite (shoulder, upper arm, forearm, wrist, hand, fingers)

Tumor dimensions and depth

Audit Caution

HCC Buddy guidance

Defaulting to unspecified when laterality is documented elsewhere in the record — always review the full encounter

Using C44 upper limb skin cancer codes instead of C4A for Merkel cell carcinoma

Assigning shoulder lesions to trunk codes (C4A.59) when the shoulder is included in upper limb codes

Not distinguishing Merkel cell carcinoma from squamous cell carcinoma or melanoma clinically — histopathology required

Common Mistakes

HCC Buddy guidance

C4A.61 — Merkel cell carcinoma of right upper limb; use when right side is documented

C4A.62 — Merkel cell carcinoma of left upper limb; use when left side is documented

C44.60x — Other malignant neoplasm of unspecified upper limb skin; for non-Merkel cell skin cancers

C43.60 — Melanoma of unspecified upper limb; different tumor type

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 C4A.60 an HCC code?

Yes. C4A.60 (Merkel cell carcinoma of unspecified upper limb, including shoulder) maps to HCC 21, Lymphoma and Other Cancers under the CMS-HCC V28 risk adjustment model, with a source-labeled community non-dual aged reference coefficient of 0.671. 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: C4A.60 is billable and maps to V28 HCC 21, Lymphoma and Other Cancers. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.

Code: C4A.60
Description: Merkel cell carcinoma of unspecified upper limb, including shoulder
HCC (V28): HCC 21 — Lymphoma and Other Cancers
RAF reference coefficient: 0.671
Billable: Yes
Payment year: 2026

HCC Category Mapping

V28HCC 21, Lymphoma and Other Cancers

0.671

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 C4A.60 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →

MEAT review for C4A.60

For C4A.60, 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

C4A.60 is the ICD-10-CM diagnosis code for merkel cell carcinoma of unspecified upper limb, including shoulder. Merkel cell carcinoma is a rare, aggressive skin cancer that develops from neuroendocrine cells in the skin. This code specifically identifies the cancer when it occurs somewhere on the upper arm, forearm, hand, or shoulder area, but the exact location on the upper limb is not specified. C4A.60 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, C4A.60 maps to Lymphoma and Other Cancers (HCC 21) with a source-labeled community, non-dual, aged reference coefficient of 0.671. No V24 mapping is shown for C4A.60; 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.

If the specific site on the upper limb is documented (e.g., shoulder, upper arm, forearm, hand, finger), use a more specific code (C4A.61-C4A.65) rather than the unspecified code C4A.60. For C4A.60, 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 C4A.60 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•If the specific site on the upper limb is documented (e.g., shoulder, upper arm, forearm, hand, finger), use a more specific code (C4A.61-C4A.65) rather than the unspecified code C4A.60
•Merkel cell carcinoma codes require a laterality indicator; ensure you capture whether the lesion is on the right or left upper limb, as this affects the complete code assignment

Clinical Significance

Merkel cell carcinoma of the unspecified upper limb, including shoulder is a rare aggressive neuroendocrine skin cancer. Upper extremity Merkel cell carcinoma has access to axillary lymphatic drainage, making sentinel lymph node biopsy of axillary nodes critical for staging. Sun exposure on the forearms and dorsal hands increases risk in this anatomical region.

Documentation Requirements

✓Histopathologic confirmation of Merkel cell carcinoma with immunohistochemistry
✓Laterality must be queried — right or left upper limb
✓Specific upper limb subsite (shoulder, upper arm, forearm, wrist, hand, fingers)
✓Tumor dimensions and depth
✓Axillary sentinel lymph node biopsy status and results
✓Staging and treatment plan documentation

Commonly Confused Codes

•C4A.61: Merkel cell carcinoma of right upper limb; use when right side is documented
•C4A.62: Merkel cell carcinoma of left upper limb; use when left side is documented
•C44.60x: Other malignant neoplasm of unspecified upper limb skin; for non-Merkel cell skin cancers
•C43.60: Melanoma of unspecified upper limb; different tumor type
•C4A.4: Merkel cell carcinoma of scalp and neck; shoulder junction can be ambiguous