Question 1

What is ICD-10 code C44.591?

Accepted Answer

C44.591 is the ICD-10-CM diagnosis code for other specified malignant neoplasm of skin of breast. A malignant skin tumor of the breast area that is not classified as basal cell or squamous cell carcinoma, representing other specified types of skin cancer in this location. C44.591 sits in the ICD-10-CM chapter for neoplasms (c00-d49), within the section covering melanoma and other malignant neoplasms of skin (c43-c44).

C44.591 is a billable ICD-10-CM code, but the current payload does not show a mapping under the CMS-HCC V28 or V24 community payment models, and none under the ESRD, Part D RxHCC, or HHS-HCC models. Do not assign risk adjustment value from this page when no source-backed mapping is shown; verify the applicable model and payment year.

Distinguish from C44.521 (squamous cell) and C44.511 (basal cell) by confirming histology.

Question 2

Is C44.591 an HCC code?

Accepted Answer

C44.591 has no payable CMS-HCC V28 mapping in the final FY2026 CMS file.

Question 3

Is C44.591 billable?

Accepted Answer

Yes. C44.591 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. C44.591 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.

Question 4

Which HCC does C44.591 map to under V28?

Accepted Answer

C44.591 has no payable CMS-HCC V28 mapping in the final FY2026 CMS file.

Question 5

What RAF reference is published for C44.591?

Accepted Answer

C44.591 has no V28 reference coefficient because the final FY2026 source verifies no payable V28 mapping.

Question 6

What is the V28 vs V24 difference for C44.591?

Accepted Answer

C44.591 has verified no payable V28 mapping in the final FY2026 source. Select a historical effective period before making any V24 comparison.

Question 7

What documentation supports C44.591?

Accepted Answer

Distinguish from C44.521 (squamous cell) and C44.511 (basal cell) by confirming histology Document whether the tumor is on the breast skin surface versus deeper breast tissue C44.591 is not a CMS-HCC V28 payment code in the verified current source, so MEAT is not the payment hook. Documentation still has to support the diagnosis if you report it.

Question 8

Can C44.591 be a primary diagnosis?

Accepted Answer

Yes. C44.591 carries no code-first instruction in the FY2026 tabular, so it can be the first-listed diagnosis when it is the condition chiefly responsible for the encounter and the note supports it, and it can also be reported as a secondary diagnosis. For risk adjustment the order does not matter; the V28 category is the same either way.

Question 9

Which codes cannot be reported with C44.591?

Accepted Answer

The Excludes1 note that applies to C44.591 lists Kaposi's sarcoma of skin (C46.0); malignant melanoma of skin (C43.-); malignant neoplasm of skin of genital organs (C51-C52, C60.-, C63.2); Merkel cell carcinoma (C4A.-); and 2 more (see the notes on this page). An Excludes1 condition is not reported together with C44.591; report one or the other, unless the two conditions are unrelated, which the ICD-10-CM Official Guidelines (Section I.A.12.a) allow.

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C44.591 ICD-10-CM Code: Other specified malignant neoplasm of skin of breast

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C44.591

Is C44.591 an HCC code?

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What This Code Means

Coding Tips

Child Codes

Code Hierarchy

Also searched as

Work C44.591 in HCC Buddy