2026 ICD-10-CM Diagnosis Code J98.59Other diseases of mediastinum, not elsewhere classified

ICD-10-CM Codes›J00–J99›J96-J99›J98

ICD-10-CM J98.59
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

J98.59 is a billable ICD-10-CM diagnosis code for other diseases of mediastinum, not elsewhere classified. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 177 through 179, 791, 793. As a secondary diagnosis, it counts as a major complication or comorbidity (MCC) and places an inpatient stay in the highest severity level of its MS-DRG family. It does not count, however, when the principal diagnosis is one of 1 closely related codes. Coders also document this condition as classical histoplasmosis mediastinal fibrosis. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Mediastinal disorders.

Code Identity

ICD-10-CM Code
J98.59
Billable Status
Yes — Valid for Submission
Code Describes
Other diseases of mediastinum, not elsewhere classified
Short Description
Other diseases of mediastinum, not elsewhere classified
Same as the full description in the CMS dataset.
Parent Code
J98.5
Diseases of mediastinum, not elsewhere classified

Code Classification

ChapterJ00–J99Diseases of the respiratory system
SectionJ96-J99Other diseases of the respiratory system
CategoryJ98Other respiratory disorders
This CodeJ98.59Other diseases of mediastinum, not elsewhere classified

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Classical histoplasmosis mediastinal fibrosis
  • Cyst of mediastinum
  • Disorder of mediastinum
  • Fibrosis of mediastinum
  • Hernia of mediastinum
  • Idiopathic hilar fibrosis
  • Mediastinal radiation fibrosis
  • Retraction of mediastinum
  • Widened mediastinum

Tabular List NotesGuidance

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

Inclusion Terms

  • Fibrosis of mediastinum
  • Hernia of mediastinum
  • Retraction of mediastinum

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

Clinical ClassificationClinical

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

CCSR RSP015
Mediastinal disorders
Default principal diagnosis: inpatient Yes · outpatient Yes

Convert J98.59 to ICD-9-CMHistory

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

ICD-9-CM
519.3 Mediastinum disease NEC
Approximate The match is approximate rather than exact.

Code History & ChangesHistory

Replacement J98.59 replaces the following previously assigned code(s):

  • J98.5 - Diseases of mediastinum, not elsewhere classified
FY 2019AddedAdded to the ICD-10-CM code setEffective October 1, 2018.
FY 2020–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About J98.59Overview

What is the ICD-10 code for other diseases of mediastinum, not elsewhere classified?

The ICD-10-CM code for other diseases of mediastinum, not elsewhere classified is J98.59 (sometimes written as J9859). It is billable on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

Is J98.59 (Diseases of mediastinum, not elsewhere classified) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report other diseases of mediastinum, not elsewhere classified on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does J98.59 group to?

When other diseases of mediastinum, not elsewhere classified is the principal diagnosis on an inpatient stay, it groups to MS-DRG 177, 178, 179, 791, 793, with relative weights from 0.7550 to 4.1696 depending on complications. Higher weights mean higher Medicare reimbursement.

Is J98.59 a CC or MCC?

CMS lists J98.59 as an MCC (major complication or comorbidity) for FY 2026. Reported as a secondary diagnosis, it places the inpatient stay in the highest-weighted DRG of its severity family. It does not count when the principal diagnosis is one of the 1 closely related codes in its exclusion list.

What is the ICD-9 equivalent of J98.59?

Under the General Equivalence Mappings, other diseases of mediastinum, not elsewhere classified converts to ICD-9-CM 519.3 (mediastinum disease NEC). The mapping is approximate, so confirm the match fits the documentation.