C4A.31 — Merkel cell carcinoma of nose
C4A.31 is a billable, specific ICD-10-CM code for merkel cell carcinoma of nose. It is valid for submission on a claim.
Other codes that can never be billed with C4A.31
These codes carry an Excludes1 note pointing at C4A.31. The conflict binds both ways, but ICD-10-CM only writes it down on one side — so you would not find this by reading C4A.31 alone.
- C44Other and unspecified malignant neoplasm of skin
Risk adjustment
C4A.31 risk-adjusts. Under the CMS-HCC V28 model it maps to this category:
- HCC 21 Lymphoma and Other Cancers0.671 RAF
Coefficient shown for the Community Non-dual Aged segment. A higher HCC in the same hierarchy will suppress this one, so capturing it does not always add score.
Medicare coverage
C4A.31 is named in 62 Medicare coverage policies — 62 listing it as supporting medical necessity. Which of them applies to you depends on your Medicare contractor, and coverage genuinely differs by state.
- A52479Oral Anticancer Drugs - Policy Article
- A52479Oral Anticancer Drugs - Policy Article
- A52479Oral Anticancer Drugs - Policy Article
- A52480Oral Antiemetic Drugs (Replacement for Intravenous Antiemetics) - Policy Article
How C4A.31 is indexed
Coders do not find codes by browsing the tabular list — they look them up in the alphabetic index, under the word the physician wrote. These are the index entries that lead here, so you can see which chart wordings map to C4A.31.
- Carcinoma›Merkel cell›nose
Code history
C4A.31 has not changed since FY2024 — no addition, revision or deletion across the three most recent ICD-10-CM releases.
Related codes at this level
Codes that share C4A.3. If C4A.31 is not quite right, the correct code is usually one of these.
Questions about C4A.31
- Is C4A.31 a billable ICD-10-CM code?
- Yes. C4A.31 is a billable, specific ICD-10-CM code and is valid for submission on a claim.
- Where does C4A.31 sit in the tabular list?
- Neoplasms (C00-D49), in the block Melanoma and other malignant neoplasms of skin (C43-C44).