Excludes1 pair
C21.0 vs C44.5-
C21.0 and C44.5 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 C44.5
anus NOS (C21.0)
C21.0
Malignant neoplasm of anus, unspecified
BillableUnspecified
- Chapter 2
- Neoplasms
- Section
- C15-C26
Indexed under
- Paget's disease › extramammary › anus
C44.5
Other and unspecified malignant neoplasm of skin of trunk
Not billable
- Chapter 2
- Neoplasms
- Section
- C43-C44
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