ICD-10 · PDGM grouping
C4A Merkel cell carcinoma
All 24 codes in the C4A family, with the PDGM clinical group, comorbidity subgroup and primary-position rule CMS assigns, read from the CMS grouper crosswalk v07.2.26 and the CDC FY2027 code file.
Codes in family
24
Can lead a claim
18
Cannot lead a claim
6
What CMS assigns to C4A
18 of the 24 codes group to MMTA - Infectious Disease, Neoplasms, and Blood-Forming Diseases; 6 are assigned no clinical group. 19 of the 24 count toward the Merkel Cell and Neuroendocrine Carcinoma comorbidity subgroup; 5 are assigned none. 18 of the 24 can lead a claim.
- Merkel Cell and Neuroendocrine Carcinoma
Every code in C4A
Descriptions are CDC’s FY2027 wording; where CMS’s grouper abbreviates one, its form is shown beneath.
| Code | Description | Primary position | Clinical group | Comorbidity subgroup |
|---|---|---|---|---|
| C4A.0 | Merkel cell carcinoma of lip | Can lead a claim | K | Merkel Cell and Neuroendocrine Carcinoma |
| C4A.1 Merkel cell carcinoma of eyelid, including canthus | ||||
| C4A.10 | Merkel cell carcinoma of unspecified eyelid, including canthusCMS: Merkel cell carcinoma of unsp eyelid, including canthus | Cannot lead a claimPrincipal diagnosis not assigned to a clinical group | None | None |
| C4A.11 Merkel cell carcinoma of right eyelid, including canthus | ||||
| C4A.111 | Merkel cell carcinoma of right upper eyelid, including canthusCMS: Merkel cell carcinoma of right upper eyelid, inc canthus | Can lead a claim | K | Merkel Cell and Neuroendocrine Carcinoma |
| C4A.112 | Merkel cell carcinoma of right lower eyelid, including canthusCMS: Merkel cell carcinoma of right lower eyelid, inc canthus | Can lead a claim | K | Merkel Cell and Neuroendocrine Carcinoma |
| C4A.12 Merkel cell carcinoma of left eyelid, including canthus | ||||
| C4A.121 | Merkel cell carcinoma of left upper eyelid, including canthusCMS: Merkel cell carcinoma of left upper eyelid, inc canthus | Can lead a claim | K | Merkel Cell and Neuroendocrine Carcinoma |
| C4A.122 | Merkel cell carcinoma of left lower eyelid, including canthusCMS: Merkel cell carcinoma of left lower eyelid, inc canthus | Can lead a claim | K | Merkel Cell and Neuroendocrine Carcinoma |
| C4A.2 Merkel cell carcinoma of ear and external auricular canal | ||||
| C4A.20 | Merkel cell carcinoma of unspecified ear and external auricular canalCMS: Merkel cell carcinoma of unsp ear and external auric canal | Cannot lead a claimPrincipal diagnosis not assigned to a clinical group | None | None |
| C4A.21 | Merkel cell carcinoma of right ear and external auricular canalCMS: Merkel cell carcinoma of right ear and external auric canal | Can lead a claim | K | Merkel Cell and Neuroendocrine Carcinoma |
| C4A.22 | Merkel cell carcinoma of left ear and external auricular canalCMS: Merkel cell carcinoma of left ear and external auric canal | Can lead a claim | K | Merkel Cell and Neuroendocrine Carcinoma |
| C4A.3 Merkel cell carcinoma of other and unspecified parts of face | ||||
| C4A.30 | Merkel cell carcinoma of unspecified part of face | Cannot lead a claimPrincipal diagnosis not assigned to a clinical group | None | None |
| C4A.31 | Merkel cell carcinoma of nose | Can lead a claim | K | Merkel Cell and Neuroendocrine Carcinoma |
| C4A.39 | Merkel cell carcinoma of other parts of face | Can lead a claim | K | Merkel Cell and Neuroendocrine Carcinoma |
| C4A.4 | Merkel cell carcinoma of scalp and neck | Can lead a claim | K | Merkel Cell and Neuroendocrine Carcinoma |
| C4A.5 Merkel cell carcinoma of trunk | ||||
| C4A.51 | Merkel cell carcinoma of anal skin | Can lead a claim | K | Merkel Cell and Neuroendocrine Carcinoma |
| C4A.52 | Merkel cell carcinoma of skin of breast | Can lead a claim | K | Merkel Cell and Neuroendocrine Carcinoma |
| C4A.59 | Merkel cell carcinoma of other part of trunk | Can lead a claim | K | Merkel Cell and Neuroendocrine Carcinoma |
| C4A.6 Merkel cell carcinoma of upper limb, including shoulder | ||||
| C4A.60 | Merkel cell carcinoma of unspecified upper limb, including shoulderCMS: Merkel cell carcinoma of unsp upper limb, including shoulder | Cannot lead a claimPrincipal diagnosis not assigned to a clinical group | None | None |
| C4A.61 | Merkel cell carcinoma of right upper limb, including shoulderCMS: Merkel cell carcinoma of right upper limb, inc shoulder | Can lead a claim | K | Merkel Cell and Neuroendocrine Carcinoma |
| C4A.62 | Merkel cell carcinoma of left upper limb, including shoulder | Can lead a claim | K | Merkel Cell and Neuroendocrine Carcinoma |
| C4A.7 Merkel cell carcinoma of lower limb, including hip | ||||
| C4A.70 | Merkel cell carcinoma of unspecified lower limb, including hipCMS: Merkel cell carcinoma of unsp lower limb, including hip | Cannot lead a claimPrincipal diagnosis not assigned to a clinical group | None | None |
| C4A.71 | Merkel cell carcinoma of right lower limb, including hip | Can lead a claim | K | Merkel Cell and Neuroendocrine Carcinoma |
| C4A.72 | Merkel cell carcinoma of left lower limb, including hip | Can lead a claim | K | Merkel Cell and Neuroendocrine Carcinoma |
| C4A.8 | Merkel cell carcinoma of overlapping sites | Can lead a claim | K | Merkel Cell and Neuroendocrine Carcinoma |
| C4A.9 | Merkel cell carcinoma, unspecified | Cannot lead a claimPrincipal diagnosis not assigned to a clinical group | None | Merkel Cell and Neuroendocrine Carcinoma |
Sources: CMS HH PPS Grouper Software v07.2.26, effective 2026-10-01, for the clinical group, comorbidity subgroup, code-first conventions and primary-position flags; CDC NCHS ICD-10-CM FY2027 code descriptions for the family title and code wording. This is the crosswalk Medicare runs a claim through. Grouping also depends on admission source, timing, the OASIS functional items and the rest of the diagnosis list.
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