2026 ICD-10-CM Diagnosis Code K12.31Oral mucositis (ulcerative) due to antineoplastic therapy

ICD-10-CM Codes›K00–K95›K00-K14›K12

ICD-10-CM K12.31
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

K12.31 is a billable ICD-10-CM diagnosis code for oral mucositis (ulcerative) due to antineoplastic therapy. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 157 through 159. Coders also document this condition as inflammation of mucous membrane due to and following chemotherapy. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Any dental condition including traumatic injury, Conditions due to neoplasm or the treatment of neoplasm, and Diseases of mouth; excluding dental.

Code Identity

ICD-10-CM Code
K12.31
Billable Status
Yes — Valid for Submission
Code Describes
Oral mucositis (ulcerative) due to antineoplastic therapy
Short Description
Oral mucositis (ulcerative) due to antineoplastic therapy
Same as the full description in the CMS dataset.
Parent Code
K12.3
Oral mucositis (ulcerative)

Code Classification

ChapterK00–K95Diseases of the digestive system
SectionK00-K14Diseases of oral cavity and salivary glands
CategoryK12Stomatitis and related lesions
This CodeK12.31Oral mucositis (ulcerative) due to antineoplastic therapy

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Inflammation of mucous membrane due to and following chemotherapy
  • Stomatitis due to cytotoxic therapy
  • Stomatitis medicamentosa
  • Ulcerative inflammation of oral mucous membrane due to and following administration of antineoplastic agent
  • Ulcerative mucositis due to non-antineoplastic therapy
  • Ulcerative stomatitis

Tabular List NotesGuidance

Coding notes and annotation back-references applicable to this code.

Use Additional Code

  • code for adverse effect, if applicable, to identify antineoplastic and immunosuppressive drugs T45.1X5

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

External Cause of Injuries IndexGuidance

References for this code in the External Cause of Injuries Index.

    • Mucositis(ulcerative)
      • mouth (oral) (oropharyngeal)
        • due to antineoplastic therapy

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR DEN001
Any dental condition including traumatic injury
Default principal diagnosis: inpatient No · outpatient No
CCSR NEO074
Conditions due to neoplasm or the treatment of neoplasm
Default principal diagnosis: inpatient Yes · outpatient Yes
CCSR DIG003
Diseases of mouth; excluding dental
Default principal diagnosis: inpatient No · outpatient No
CCSR DEN002
Nontraumatic dental conditions
Default principal diagnosis: inpatient No · outpatient No

Clinical InformationClinical

  • Tumor Protein 63|CUSP|Chronic Ulcerative Stomatitis Protein|Keratinocyte Transcription Factor KET|TP63|Transformation-Related Protein 63|Tumor Protein p73-Like|p40|p51|p63|p73L

    tumor protein 63 (680 aa, ~77 kda) is encoded by the human tp63 gene. this protein plays a role in the mediation of both transcription and limb morphogenesis.

  • Ulcerative Stomatitis

    inflammation of the mouth mucosa associated with the presence of ulcers.

Patient EducationClinical

Cancer Chemotherapy

Cancer chemotherapy is a type of cancer treatment. It uses medicines to destroy cancer cells.

The full article covers:

  • What is cancer chemotherapy?
  • What are the side effects of chemotherapy?
  • What can I expect when getting chemotherapy?

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert K12.31 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
528.01 Mucosits d/t antineo rx
Approximate The match is approximate rather than exact.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About K12.31Overview

Is K12.31 (Oral mucositis (ulcerative)) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report oral mucositis (ulcerative) due to antineoplastic therapy on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does K12.31 group to?

When oral mucositis (ulcerative) due to antineoplastic therapy is the principal diagnosis on an inpatient stay, it groups to MS-DRG 157, 158, 159, with relative weights from 0.7085 to 1.7168 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of K12.31?

Under the General Equivalence Mappings, oral mucositis (ulcerative) due to antineoplastic therapy converts to ICD-9-CM 528.01 (mucosits d/t antineo rx). The mapping is approximate, so confirm the match fits the documentation.

Footnotes

[1] Chronic - a chronic condition code indicates a condition lasting 12 months or longer and its effect on the patient based on one or both of the following criteria:

  • The condition results in the need for ongoing intervention with medical products,treatment, services, and special equipment
  • The condition places limitations on self-care, independent living, and social interactions.