C4A
C4A — Merkel cell carcinoma
Non-billable headerICD-10-CM
C4A is a non-billable header ICD-10-CM code for merkel cell carcinoma. It cannot be billed on its own: choose one of the more specific child codes below.
Other codes that can never be billed with C4A
These codes carry an Excludes1 note pointing at C4A. 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 alone.
Risk adjustment
C4A does not map to an HCC and does not risk-adjust under CMS-HCC V28. That is normal — most ICD-10 codes do not. It still needs to be coded correctly; it just will not move a RAF score.
Code to one of these instead C4A
10 child codes. Green means billable.
- C4A.0Merkel cell carcinoma of lip
- C4A.1Merkel cell carcinoma of eyelid, including canthus
- C4A.2Merkel cell carcinoma of ear and external auricular canal
- C4A.3Merkel cell carcinoma of other and unspecified parts of face
- C4A.4Merkel cell carcinoma of scalp and neck
- C4A.5Merkel cell carcinoma of trunk
- C4A.6Merkel cell carcinoma of upper limb, including shoulder
- C4A.7Merkel cell carcinoma of lower limb, including hip
- C4A.8Merkel cell carcinoma of overlapping sites
- C4A.9Merkel cell carcinoma, unspecified
Questions about C4A
- Is C4A a billable ICD-10-CM code?
- No. C4A is a non-billable header code. Code to a higher level of specificity using one of its child codes.
- Where does C4A sit in the tabular list?
- Neoplasms (C00-D49), in the block Melanoma and other malignant neoplasms of skin (C43-C44).