2026 ICD-10-CM Diagnosis Code K04.8Radicular cyst

ICD-10-CM Codes›K00–K95›K00-K14›K04

ICD-10-CM K04.8
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

K04.8 is a billable ICD-10-CM diagnosis code for radicular cyst. 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 inflammatory odontogenic cyst. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Any dental condition including traumatic injury, Disorders of teeth and gingiva, and Nontraumatic dental conditions.

Code Identity

ICD-10-CM Code
K04.8
Billable Status
Yes — Valid for Submission
Code Describes
Radicular cyst
Short Description
Radicular cyst
Same as the full description in the CMS dataset.
Parent Code
K04
Diseases of pulp and periapical tissues

Code Classification

ChapterK00–K95Diseases of the digestive system
SectionK00-K14Diseases of oral cavity and salivary glands
CategoryK04Diseases of pulp and periapical tissues
This CodeK04.8Radicular cyst

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Inflammatory odontogenic cyst
  • Lateral radicular cyst
  • Periodontal cyst
  • Radicular cyst
  • Residual cyst

Tabular List NotesGuidance

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

Inclusion Terms

  • Apical (periodontal) cyst
  • Periapical cyst
  • Residual radicular cyst

Type 2 Excludes

  • lateral periodontal cyst K09.0

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.

    • Cyst(colloid) (mucous) (simple) (retention)
      • apical (tooth) (periodontal)
    • Cyst(colloid) (mucous) (simple) (retention)
      • dental (root)
    • Cyst(colloid) (mucous) (simple) (retention)
      • mandible
        • radicular
    • Cyst(colloid) (mucous) (simple) (retention)
      • maxilla
        • radicular
    • Cyst(colloid) (mucous) (simple) (retention)
      • periapical
    • Cyst(colloid) (mucous) (simple) (retention)
      • periodontal
    • Cyst(colloid) (mucous) (simple) (retention)
      • radicular (residual)
    • Cyst(colloid) (mucous) (simple) (retention)
      • radiculodental
    • Cyst(colloid) (mucous) (simple) (retention)
      • residual (radicular)

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 DIG002
Disorders of teeth and gingiva
Default principal diagnosis: inpatient Yes · outpatient Yes
CCSR DEN002
Nontraumatic dental conditions
Default principal diagnosis: inpatient No · outpatient No

Clinical InformationClinical

  • Radicular Cyst

    slow-growing fluid-filled epithelial sac at the apex of a tooth with a nonvital pulp or defective root canal filling.

  • Periodontal Cyst

    an epithelium-lined sac containing fluid; usually found at the apex of a pulp-involved tooth. the lateral type occurs less frequently along the side of the root.

Patient EducationClinical

Gum Disease

If you have gum disease, you're not alone. Many U.S. adults currently have some form of the disease. It ranges from simple gum inflammation, called gingivitis, to serious damage to the tissue and bone supporting the teeth. In the worst cases, you can lose teeth.

Read the full article at MedlinePlus

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

Convert K04.8 to ICD-9-CMHistory

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

ICD-9-CM
522.8 Radicular cyst
Exact Match The mapping is direct, with no qualifiers.

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 K04.8Overview

Is K04.8 (Diseases of pulp and periapical tissues) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report radicular cyst on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does K04.8 group to?

When radicular cyst 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 K04.8?

Under the General Equivalence Mappings, radicular cyst converts to ICD-9-CM 522.8 (radicular cyst). The mapping is a direct match.

Footnotes

[1] Not chronic - A diagnosis code that does not fit the criteria for chronic condition (duration, ongoing medical treatment, and limitations) is considered not chronic. Some codes designated as not chronic are acute conditions. Other diagnosis codes that indicate a possible chronic condition, but for which the duration of the illness is not specified in the code description (i.e., we do not know the condition has lasted 12 months or longer) also are considered not chronic.