C84.Z vs C91.1
C84.Z (Other mature T/NK-cell lymphomas) compared with C91.1 (Chronic lymphocytic leukemia of B-cell type), from the official CMS tabular data. Do not report these codes together: the official tabular list marks them Excludes1.
Can these codes be reported together?
No — do not report together. C84.Z carries an Excludes1 note covering C91.1: “T-cell leukemia (C91.1-)”
Sole exception: when the two conditions are documented as unrelated to each other (ICD-10-CM Official Guidelines, Section I.A.12.a).
Side by side
| C84.ZOther mature T/NK-cell lymphomas | C91.1Chronic lymphocytic leukemia of B-cell type | |
|---|---|---|
| Billing status | Non-billable header | Non-billable header |
| Classification | C00-D49 — Neoplasms (C00-D49) | C00-D49 — Neoplasms (C00-D49) |
| Definition | Other mature T/NK-cell lymphomas is a non-billable ICD-10-CM category code (C84.Z). | Chronic lymphocytic leukemia of B-cell type is a non-billable ICD-10-CM category code (C91.1). |
| Includes | — | Lymphoplasmacytic leukemia Richter syndrome |
Derived from the official CMS ICD-10-CM tabular data (FY2026). Not billing advice; verify sequencing rules for the encounter. All data sources