ICD-10-CM category
C4A: Merkel cell carcinoma
Codes under C4A (Merkel cell carcinoma). A ✓ marks a billable (fully specified) code; category codes without a ✓ are not billable on their own.
| Code | Description | Billable |
|---|---|---|
| C4A.0 | Merkel cell carcinoma of lip | ✓ |
| C4A.0 | Merkel cell carcinoma of lip | ✓ |
| C4A.1 | Merkel cell carcinoma of eyelid, including canthus | — |
| C4A.1 | Merkel cell carcinoma of eyelid, including canthus | — |
| C4A.2 | Merkel cell carcinoma of ear and external auricular canal | — |
| C4A.2 | Merkel cell carcinoma of ear and external auricular canal | — |
| C4A.3 | Merkel cell carcinoma of other and unspecified parts of face | — |
| C4A.3 | Merkel cell carcinoma of other and unspecified parts of face | — |
| C4A.4 | Merkel cell carcinoma of scalp and neck | ✓ |
| C4A.4 | Merkel cell carcinoma of scalp and neck | ✓ |
| C4A.5 | Merkel cell carcinoma of trunk | — |
| C4A.5 | Merkel cell carcinoma of trunk | — |
| C4A.6 | Merkel cell carcinoma of upper limb, including shoulder | — |
| C4A.6 | Merkel cell carcinoma of upper limb, including shoulder | — |
| C4A.7 | Merkel cell carcinoma of lower limb, including hip | — |
| C4A.7 | Merkel cell carcinoma of lower limb, including hip | — |
| C4A.8 | Merkel cell carcinoma of overlapping sites | ✓ |
| C4A.8 | Merkel cell carcinoma of overlapping sites | ✓ |
| C4A.9 | Merkel cell carcinoma, unspecified | ✓ |
| C4A.9 | Merkel cell carcinoma, unspecified | ✓ |
| C4A.10 | Merkel cell carcinoma of unspecified eyelid, including canthus | ✓ |
| C4A.10 | Merkel cell carcinoma of unspecified eyelid, including canthus | ✓ |
| C4A.11 | Merkel cell carcinoma of right eyelid, including canthus | — |
| C4A.11 | Merkel cell carcinoma of right eyelid, including canthus | — |
| C4A.12 | Merkel cell carcinoma of left eyelid, including canthus | — |
| C4A.12 | Merkel cell carcinoma of left eyelid, including canthus | — |
| C4A.20 | Merkel cell carcinoma of unspecified ear and external auricular canal | ✓ |
| C4A.20 | Merkel cell carcinoma of unspecified ear and external auricular canal | ✓ |
| C4A.21 | Merkel cell carcinoma of right ear and external auricular canal | ✓ |
| C4A.21 | Merkel cell carcinoma of right ear and external auricular canal | ✓ |
| C4A.22 | Merkel cell carcinoma of left ear and external auricular canal | ✓ |
| C4A.22 | Merkel cell carcinoma of left ear and external auricular canal | ✓ |
| C4A.30 | Merkel cell carcinoma of unspecified part of face | ✓ |
| C4A.30 | Merkel cell carcinoma of unspecified part of face | ✓ |
| C4A.31 | Merkel cell carcinoma of nose | ✓ |
| C4A.31 | Merkel cell carcinoma of nose | ✓ |
| C4A.39 | Merkel cell carcinoma of other parts of face | ✓ |
| C4A.39 | Merkel cell carcinoma of other parts of face | ✓ |
| C4A.51 | Merkel cell carcinoma of anal skin | ✓ |
| C4A.51 | Merkel cell carcinoma of anal skin | ✓ |
| C4A.52 | Merkel cell carcinoma of skin of breast | ✓ |
| C4A.52 | Merkel cell carcinoma of skin of breast | ✓ |
| C4A.59 | Merkel cell carcinoma of other part of trunk | ✓ |
| C4A.59 | Merkel cell carcinoma of other part of trunk | ✓ |
| C4A.60 | Merkel cell carcinoma of unspecified upper limb, including shoulder | ✓ |
| C4A.60 | Merkel cell carcinoma of unspecified upper limb, including shoulder | ✓ |
| C4A.61 | Merkel cell carcinoma of right upper limb, including shoulder | ✓ |
| C4A.61 | Merkel cell carcinoma of right upper limb, including shoulder | ✓ |
| C4A.62 | Merkel cell carcinoma of left upper limb, including shoulder | ✓ |
| C4A.62 | Merkel cell carcinoma of left upper limb, including shoulder | ✓ |
| C4A.70 | Merkel cell carcinoma of unspecified lower limb, including hip | ✓ |
| C4A.70 | Merkel cell carcinoma of unspecified lower limb, including hip | ✓ |
| C4A.71 | Merkel cell carcinoma of right lower limb, including hip | ✓ |
| C4A.71 | Merkel cell carcinoma of right lower limb, including hip | ✓ |
| C4A.72 | Merkel cell carcinoma of left lower limb, including hip | ✓ |
| C4A.72 | Merkel cell carcinoma of left lower limb, including hip | ✓ |
| C4A.111 | Merkel cell carcinoma of right upper eyelid, including canthus | ✓ |
| C4A.111 | Merkel cell carcinoma of right upper eyelid, including canthus | ✓ |
| C4A.112 | Merkel cell carcinoma of right lower eyelid, including canthus | ✓ |
| C4A.112 | Merkel cell carcinoma of right lower eyelid, including canthus | ✓ |
| C4A.121 | Merkel cell carcinoma of left upper eyelid, including canthus | ✓ |
| C4A.121 | Merkel cell carcinoma of left upper eyelid, including canthus | ✓ |
| C4A.122 | Merkel cell carcinoma of left lower eyelid, including canthus | ✓ |
| C4A.122 | Merkel cell carcinoma of left lower eyelid, including canthus | ✓ |
Frequently asked questions
What is ICD-10-CM code C4A?
C4A is an ICD-10-CM category covering Merkel cell carcinoma. It contains 64 more specific diagnosis codes, 48 of which are billable.
Is C4A a billable code?
No — C4A is a category header and isn't billable on its own. Code to the highest level of specificity using one of its subcodes (for example C4A.0 — Merkel cell carcinoma of lip). 48 of the 64 codes under C4A are billable.
What codes fall under C4A?
C4A includes C4A.0, C4A.0, C4A.1, C4A.1, C4A.2, plus 59 more. See the full list with descriptions and billable status above.
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Informational only, not coding or medical advice. Verify against the official ICD-10-CM (FY2026) and your payer's guidelines.
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