2026 ICD-10-CM Diagnosis Code Q34.1Congenital cyst of mediastinum

ICD-10-CM Codes›Q00-Q99›Q30-Q34›Q34

ICD-10-CM Q34.1
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

Q34.1 is a billable ICD-10-CM diagnosis code for congenital cyst of mediastinum. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 205 through 206. The code is exempt from POA reporting. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Respiratory congenital malformations.

Code Identity

ICD-10-CM Code
Q34.1
Billable Status
Yes — Valid for Submission
Code Describes
Congenital cyst of mediastinum
Short Description
Congenital cyst of mediastinum
Same as the full description in the CMS dataset.
Parent Code
Q34
Other congenital malformations of respiratory system

Code Classification

ChapterQ00-Q99Congenital malformations, deformations and chromosomal abnormalities
SectionQ30-Q34Congenital malformations of the respiratory system
CategoryQ34Other congenital malformations of respiratory system
This CodeQ34.1Congenital cyst of mediastinum

Present on Admission (POA)Billing

Q34.1 is exempt from POA reporting on inpatient claims to general acute care hospitals. Review other POA exempt codes.

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Congenital cyst of mediastinum
  • Cyst of mediastinum

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)
      • congenital NEC
        • mediastinum
    • Cyst(colloid) (mucous) (simple) (retention)
      • mediastinum, congenital

Clinical ClassificationClinical

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

CCSR MAL007
Respiratory congenital malformations
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Birth Defects

A birth defect is a problem that happens while a baby is developing in the mother's body. Most birth defects happen during the first 3 months of pregnancy. One out of every 33 babies in the United States is born with a birth defect.

The full article covers:

  • What are birth defects?
  • What causes birth defects?
  • Who is at risk of having a baby with birth defects?
  • How are birth defects diagnosed?
  • What are the treatments for birth defects?
  • Can birth defects be prevented?

Read the full article at MedlinePlus

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

Convert Q34.1 to ICD-9-CMHistory

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

ICD-9-CM
748.8 Respiratory anomaly NEC
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 Q34.1Overview

Is Q34.1 (Other congenital malformations of respiratory system) a billable code?

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

What MS-DRG does Q34.1 group to?

When congenital cyst of mediastinum is the principal diagnosis on an inpatient stay, it groups to MS-DRG 205, 206, with relative weights from 0.9411 to 1.8310 depending on complications. Higher weights mean higher Medicare reimbursement.

Is Q34.1 exempt from POA reporting?

Yes. CMS lists this code among those exempt from present on admission reporting, so hospitals do not assign a POA indicator for congenital cyst of mediastinum on inpatient claims.

What is the ICD-9 equivalent of Q34.1?

Under the General Equivalence Mappings, congenital cyst of mediastinum converts to ICD-9-CM 748.8 (respiratory anomaly NEC). The mapping is approximate, so confirm the match fits the documentation.

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.