ICD-10-CM 2027 diagnosis code

C91Lymphoid leukemia

Not billable — use a more specific code

C91 is a header code, so it can't be reported by itself. Choose one of the 9 more specific codes beneath it.

Code unchanged since ICD-10-CM took effect on October 1, 2015. Source: official FY2027 ICD-10-CM release from CDC/NCHS and CMS. Page updated September 29, 2026. About our data

About C91

C91 is the ICD-10-CM diagnosis code for lymphoid leukemia. It belongs to block C81-C96 (malignant neoplasms of lymphoid, hematopoietic and related tissue) and chapter 2 (neoplasms). It is a header code, so it can't be reported by itself; one of its 9 subcodes must be used instead.

To report this condition, pick the subcode that matches the documentation: C91.0 ([ALL]), C91.1 (type), C91.3 (type), C91.4 (leukemia), C91.5 ((HTLV-1-associated)), C91.6 (type), C91.9 (unspecified), C91.A (Burkitt-type) and 1 more.

Don't report C91 together with the conditions in its Excludes1 note: personal history of leukemia (Z85.6).

It has been part of ICD-10-CM since the code set took effect on October 1, 2015 and hasn't changed since.

Specific codes under C91

Coding notes

Excludes1Not coded here — never report together with this code

personal history of leukemia (Z85.6)

Notes that apply from higher levels

Instructions written at a parent level also apply to C91.

Broader instructions also apply from C81-C96 Malignant neoplasms of lymphoid, hematopoietic and related tissue and Chapter 2: Neoplasms.

Codes whose notes reference C91

D72.8Excludes1
D72.825Excludes1
M36.1Code first
N16Code first
R50.81Code first
T66Excludes1

Code history

2016
2017
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2020
2021
2022
2023
2024
2025
2026
2027

FY2016 (effective 10/1/2015): Added (first year of ICD-10-CM)
No changes since FY2016.

Common questions about C91

Is C91 billable?: No. C91 is a header code. Report one of its more specific subcodes instead.