Excludes1 pair
C84.Z- vs C91-
C84.Z and C91 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 C84.Z
T-cell leukemia (C91.1-)
C84.Z
Other mature T/NK-cell lymphomas
Not billable
- Chapter 2
- Neoplasms
- Section
- C81-C96
Indexed under
- Lymphoma › mature T/NK-cell › specified NEC
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