2027 ICD-10-CM Diagnosis Code C91.Z2Other lymphoid leukemia, in relapse
ICD-10-CM Codes›C00–D49›C81-C96›C91
- Billable — Valid for Submission
- CC — Complication or Comorbidity
- Risk Adjusts — HCC 22
- Chronic Condition
C91.Z2 is a billable ICD-10-CM diagnosis code for other lymphoid leukemia, in relapse. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 820 through 825, 840 through 842. As a secondary diagnosis, it counts as a complication or comorbidity (CC) and moves an inpatient stay to a higher severity level within its MS-DRG family. It does not count, however, when the principal diagnosis is one of 113 closely related codes. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Leukemia - all other types.
For Medicare Advantage risk adjustment, C91.Z2 maps to CMS-HCC Category 22 (Bladder, Colorectal, and Other Cancers) under the V28 model, adding a risk factor of about 0.363 for a community, non-dual, aged beneficiary in payment year 2027.
Code Identity
Code Classification
Medicare Risk Adjustment (HCC)Billing
C91.Z2 maps to a payment category in the CMS-HCC model used to risk-adjust Medicare Advantage payments. Weights are the published community factors for payment year 2027.
Source: CMS Payment Year 2027 risk adjustment mappings and model software. Weights are relative factors, not dollar amounts; a beneficiary's total RAF also includes demographics and interactions. Browse all CMS-HCC categories.
Instructional NotesGuidance
Instructions from the official ICD-10-CM Tabular List that apply to C91.Z2: its own notes plus those printed at C91, block C81-C96, and Chapter 2. A note printed at a category, block or chapter applies to every code under it.
Excludes1
Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.
Excludes2
Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.
Notes
General instructions on how these codes are used.
- Functional activity
- All neoplasms are classified in this chapter, whether they are functionally active or not. An additional code from Chapter 4 may be used, to identify functional activity associated with any neoplasm.
- Morphology [Histology]
- Chapter 2 classifies neoplasms primarily by site (topography), with broad groupings for behavior, malignant, in situ, benign, etc. The Table of Neoplasms should be used to identify the correct topography code. In a few cases, such as for malignant melanoma and certain neuroendocrine tumors, the morphology (histologic type) is included in the category and codes.
- Primary malignant neoplasms overlapping site boundaries
- A primary malignant neoplasm that overlaps two or more contiguous (next to each other) sites should be classified to the subcategory/code .8 ('overlapping lesion'), unless the combination is specifically indexed elsewhere. For multiple neoplasms of the same site that are not contiguous, such as tumors in different quadrants of the same breast, codes for each site should be assigned.
- Malignant neoplasm of ectopic tissue
- Malignant neoplasms of ectopic tissue are to be coded to the site mentioned, e.g., ectopic pancreatic malignant neoplasms are coded to pancreas, unspecified (C25.9).
Source: CMS ICD-10-CM Tabular List. How to read instructional notes.
Referenced in Other NotesGuidance
Instructional notes printed at other codes that name C91.Z2, its category, or a range that includes it.
Applicable To 2
These notes mention C91.Z2.
Excludes1 4
These codes carry an Excludes1 note naming C91.Z2: they are not reported together with it, unless the two conditions are unrelated.
Code First 3
These codes say to code first a condition named in the note, and C91.Z2 is one of the conditions named.
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Clinical InformationClinical
Leukemia, Lymphoid
leukemia associated with hyperplasia of the lymphoid tissues and increased numbers of circulating malignant lymphocytes and lymphoblasts.
Patient EducationClinical
Acute Lymphocytic Leukemia
Leukemia is a term for cancers of the blood cells. Leukemia starts in blood-forming tissues such as the bone marrow. Your bone marrow makes the cells which will develop into white blood cells, red blood cells, and platelets. Each type of cell has a different job:
The full article covers:
- What is leukemia?
- What is acute lymphocytic leukemia (ALL)?
- What causes acute lymphocytic leukemia (ALL)?
- Who is at risk for acute lymphocytic leukemia (ALL)?
- What are the symptoms of acute lymphocytic leukemia (ALL)?
- How is acute lymphocytic leukemia (ALL) diagnosed?
- What are the treatments for acute lymphocytic leukemia (ALL)?
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert C91.Z2 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About C91.Z2Overview
What is the ICD-10 code for other lymphoid leukemia, in relapse?
The ICD-10-CM code for other lymphoid leukemia, in relapse is C91.Z2 (sometimes written as C91Z2). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
Is C91.Z2 (Other lymphoid leukemia) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report other lymphoid leukemia, in relapse on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
What MS-DRG does C91.Z2 group to?
When other lymphoid leukemia, in relapse is the principal diagnosis on an inpatient stay, it groups to MS-DRG 841, 821, 822, 825, 842, 824, 840, 820, 823, with relative weights from 0.9948 to 6.2454 depending on complications. Higher weights mean higher Medicare reimbursement.
Is C91.Z2 a CC or MCC?
CMS lists C91.Z2 as a CC (complication or comorbidity) for FY 2027. Reported as a secondary diagnosis, it moves the inpatient stay to a higher-weighted DRG within its severity family. It does not count when the principal diagnosis is one of the 113 closely related codes in its exclusion list.
Can C91.Z2 be reported with Z85.6?
Not as a rule. The Excludes1 note at C91, which applies to C91.Z2, lists "personal history of leukemia (Z85.6)". An Excludes1 note means the excluded code is never reported together with this one; the only exception is when the two conditions are unrelated to each other (Official Guidelines, Section I.A.12.a).
What HCC is C91.Z2?
C91.Z2 (other lymphoid leukemia, in relapse) maps to CMS-HCC Category 22 (Bladder, Colorectal, and Other Cancers), commonly written as HCC 22, in the CMS-HCC V28 model used for Medicare Advantage risk adjustment in payment year 2027. It mapped to HCC 10 under the retired V24 model. It also maps in the PACE (CMS-HCC V22), ESRD (V21), and ESRD (V24) models. In the Part D prescription drug model it maps to RxHCC 19.
Does C91.Z2 risk-adjust for Medicare Advantage payment?
Yes. When documented and reported on a Medicare Advantage encounter, C91.Z2 adds a risk adjustment factor of about 0.363 to the beneficiary's RAF score for a community, non-dual, aged enrollee (published V28 weights range from 0.314 to 0.410 depending on the payment segment). A more severe related category (HCC 17, HCC 18, HCC 19, HCC 20, and HCC 21) supersedes it when both are reported. See the full factor table on the HCC 22 category page.
