Excludes1 pair
C83- vs C91.1-
C83 and C91.1 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 C91.1
lymphoplasmacytic lymphoma (C83.0-)
C91.1
Chronic lymphocytic leukemia of B-cell type
Not billable
- Chapter 2
- Neoplasms
- Section
- C81-C96
Use when the record says
- Lymphoplasmacytic leukemia
- Richter syndrome
Indexed under
- Leukemia, leukemic › chronic lymphocytic, of B-cell type
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