Question 1

What is ICD-10 code C04?

Accepted Answer

C04 is the ICD-10-CM diagnosis code for malignant neoplasm of floor of mouth. C04 sits in the ICD-10-CM chapter for neoplasms (c00-d49), within the section covering malignant neoplasms of lip, oral cavity and pharynx (c00-c14).

Header codes like C04 cannot be reported on claims directly; they organize child codes that share clinical context. Coders should select the billable child code that matches the documented presentation and then verify its current source-backed HCC mapping. Do not infer a child code or risk adjustment value from the header alone.

Question 2

Is C04 an HCC code?

Accepted Answer

C04 is a non-billable header code, so it cannot itself be a payment HCC. Header codes organize more specific child codes that share the same root concept; one of those children may map to a payment HCC under the CMS-HCC V28 or V24 risk adjustment model. Coders should select a child code from the C04 hierarchy that matches the documented presentation, then check that specific child for HCC status.

Question 3

Is C04 billable?

Accepted Answer

No. C04 is a header (non-billable) ICD-10-CM code. Header codes sit at a higher level of the diagnosis hierarchy and exist to organize a family of more specific child codes. Per ICD-10-CM coding guidelines, a header code cannot be reported on a claim as the diagnosis, coders must select a billable child code from the C04 hierarchy that matches the highest level of specificity supported by the provider's documentation. Payers reject header codes submitted as the primary diagnosis.

Question 4

Which HCC does C04 map to under V28?

Accepted Answer

C04 does not map to a CMS-HCC V28 payment category. Check the current CMS-HCC V28 model file for payment year 2026 rather than an older V24 tip sheet.

Question 5

What RAF reference is published for C04?

Accepted Answer

C04 has no separately stated V28 community reference coefficient. Check the current CMS mapping and factor files before using it in any member-score workflow.

Question 6

What documentation supports C04?

Accepted Answer

C04 is not a CMS-HCC payment code, so MEAT is not the payment hook. Documentation still has to support the diagnosis if you report it.

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C04

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C04 ICD-10-CM Code: Malignant neoplasm of floor of mouth