Excludes1 pair
C00.2 vs C4A.0
C00.2 and C4A.0 are not coded together. ICD-10-CM declares them mutually exclusive with an Excludes1 note — the two conditions are not expected to occur together, so exactly one of them is normally correct for a given encounter. The Official Guidelines carve out one exception: if the two conditions are clearly unrelated to each other, both may be reported.
The official note, declared on C4A.0
malignant neoplasm of vermilion border of lip (C00.0-C00.2)
C00.2
Malignant neoplasm of external lip, unspecified
BillableUnspecified
- Chapter 2
- Neoplasms
- Section
- C00-C14
Use when the record says
- Malignant neoplasm of vermilion border of lip NOS
C4A.0
Merkel cell carcinoma of lip
Billable
- Chapter 2
- Neoplasms
- Section
- C43-C44
Indexed under
- Carcinoma › Merkel cell › lip
Excludes1 is not always absolute: where two conditions covered by the note are genuinely unrelated, CMS guidance permits reporting both. Document the reasoning rather than assuming it. More on Excludes1 vs Excludes2 · FY2027