2027 ICD-10-CM Diagnosis Code C91.01Acute lymphoblastic leukemia, in remission
ICD-10-CM Codes›C00–D49›C81-C96›C91
- Billable — Valid for Submission
- CC — Complication or Comorbidity
- Risk Adjusts — HCC 18
- Chronic Condition
C91.01 is a billable ICD-10-CM diagnosis code for acute lymphoblastic leukemia, in remission. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 820 through 822, 834 through 839, 850. 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. Coders also document this condition as acute lymphoid leukemia in remission. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Leukemia in remission.
For Medicare Advantage risk adjustment, C91.01 maps to CMS-HCC Category 18 (Cancer Metastatic to Bone, Other and Unspecified Metastatic Cancer; Acute Leukemia Except Myeloid) under the V28 model, adding a risk factor of about 2.341 for a community, non-dual, aged beneficiary in payment year 2027.
Code Identity
Code Classification
Medicare Risk Adjustment (HCC)Billing
C91.01 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.
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Acute lymphoid leukemia in remission
- Disorder of central nervous system co-occurrent and due to acute lymphoid leukemia
- Disorder of central nervous system co-occurrent and due to acute lymphoid leukemia in remission
- Precursor B-cell acute lymphoblastic leukemia
- Precursor B-cell acute lymphoblastic leukemia in remission
- Precursor T-cell neoplasm
- T-lymphoblastic leukemia
- T-lymphoblastic leukemia in remission
- T-lymphoblastic leukemia/lymphoblastic lymphoma
Instructional NotesGuidance
Instructions from the official ICD-10-CM Tabular List that apply to C91.01: its own notes plus those printed at C91.0, 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.
- Codes in subcategory C91.0- should only be used for T-cell and B-cell precursor leukemia
- 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 C91.01, its category, or a range that includes it.
Applicable To 2
These notes mention C91.01.
Excludes1 4
These codes carry an Excludes1 note naming C91.01: 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 C91.01 is one of the conditions named.
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Clinical InformationClinical
Precursor Cell Lymphoblastic Leukemia-Lymphoma
a neoplasm characterized by abnormalities of the lymphoid cell precursors leading to excessive lymphoblasts in the marrow and other organs. it is the most common cancer in children and accounts for the vast majority of all childhood leukemias.
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 C91.01 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About C91.01Overview
What is the ICD-10 code for acute lymphoblastic leukemia, in remission?
The ICD-10-CM code for acute lymphoblastic leukemia, in remission is C91.01 (sometimes written as C9101). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
Is C91.01 (Acute lymphoblastic leukemia [ALL]) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report acute lymphoblastic leukemia, in remission on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
What MS-DRG does C91.01 group to?
When acute lymphoblastic leukemia, in remission is the principal diagnosis on an inpatient stay, it groups to MS-DRG 834, 837, 821, 822, 836, 839, 838, 850, 835, 820, with relative weights from 1.1267 to 8.4076 depending on complications. Higher weights mean higher Medicare reimbursement.
Is C91.01 a CC or MCC?
CMS lists C91.01 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 C91.01 be reported with Z85.6?
Not as a rule. The Excludes1 note at C91, which applies to C91.01, 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 C91.01?
C91.01 (acute lymphoblastic leukemia, in remission) maps to CMS-HCC Category 18 (Cancer Metastatic to Bone, Other and Unspecified Metastatic Cancer; Acute Leukemia Except Myeloid), commonly written as HCC 18, in the CMS-HCC V28 model used for Medicare Advantage risk adjustment in payment year 2027. It mapped to HCC 8 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 C91.01 risk-adjust for Medicare Advantage payment?
Yes. When documented and reported on a Medicare Advantage encounter, C91.01 adds a risk adjustment factor of about 2.341 to the beneficiary's RAF score for a community, non-dual, aged enrollee (published V28 weights range from 1.110 to 2.537 depending on the payment segment). A more severe related category (HCC 17) supersedes it when both are reported. See the full factor table on the HCC 18 category page.
