2027 ICD-10-CM Diagnosis Code D38.3Neoplasm of uncertain behavior of mediastinum

ICD-10-CM Codes›C00–D49›D37-D48›D38

ICD-10-CM D38.3
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

D38.3 is a billable ICD-10-CM diagnosis code for neoplasm of uncertain behavior of mediastinum. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 180 through 182. Coders also document this condition as anterior mediastinum mass. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Neoplasms of unspecified nature or uncertain behavior.

Code Identity

ICD-10-CM Code
D38.3
Billable Status
Yes — Valid for Submission
Code Describes
Neoplasm of uncertain behavior of mediastinum
Short Description
Neoplasm of uncertain behavior of mediastinum
Same as the full description in the CMS dataset.
Parent Code
D38
Neoplasm of uncertain behavior of middle ear and respiratory and intrathoracic organs

Code Classification

ChapterC00–D49Neoplasms
SectionD37-D48Neoplasms of uncertain behavior, polycythemia vera and myelodysplastic syndromes
CategoryD38Neoplasm of uncertain behavior of middle ear and respiratory and intrathoracic organs
This CodeD38.3Neoplasm of uncertain behavior of mediastinum

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Anterior mediastinum mass
  • Neoplasm of anterior mediastinum
  • Neoplasm of posterior mediastinum
  • Neoplasm of uncertain behavior of anterior mediastinum
  • Neoplasm of uncertain behavior of mediastinum
  • Neoplasm of uncertain behavior of posterior mediastinum

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to D38.3: its own notes plus those printed at D38, block D37-D48, 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.

From D38 Neoplasm of uncertain behavior of middle ear and respiratory and intrathoracic organs applies to 7 codes
  • neoplasm of uncertain behavior of heart (D48.7)
From Block D37-D48 Neoplasms of uncertain behavior, polycythemia vera and myelodysplastic syndromes applies to 137 codes
  • neoplasms of unspecified behavior (D49.-)

Notes

General instructions on how these codes are used.

From Block D37-D48 Neoplasms of uncertain behavior, polycythemia vera and myelodysplastic syndromes applies to 137 codes
  • Categories D37-D44, and D48 classify by site neoplasms of uncertain behavior, i.e., histologic confirmation whether the neoplasm is malignant or benign cannot be made.
From Chapter 2 (C00-D49) Neoplasms applies to 1,730 codes
  • 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 D38.3, its category, or a range that includes it.

Excludes2 1

These codes carry an Excludes2 note naming D38.3: its condition is not part of those codes, and both may be reported when the patient has both.

  • D49 Neoplasms of unspecified behavior
    neoplasms of uncertain behavior (D37-D44, D48) names D37-D44, which includes this code

Notes 1

These notes mention D38.3.

  • Block D37-D48 Neoplasms of uncertain behavior, polycythemia vera and myelodysplastic syndromes
    Categories D37-D44, and D48 classify by site neoplasms of uncertain behavior, i.e., histologic confirmation whether the neoplasm is malignant or benign cannot be made. names D37-D44, which includes this code

Clinical ClassificationClinical

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

CCSR NEO072
Neoplasms of unspecified nature or uncertain behavior
Default principal diagnosis: inpatient Yes · outpatient Yes

Table of NeoplasmsClinical

Anatomical sites in the Table of Neoplasms that reference this code family.

SiteMalig.
Primary		Malig.
Secondary		Ca
in situ		BenignUncertainUnspec.
mediastinum, mediastinalC38.3C78.1–D15.2D38.3D49.89
mediastinum, mediastinal › anteriorC38.1C78.1–D15.2D38.3D49.89
mediastinum, mediastinal › posteriorC38.2C78.1–D15.2D38.3D49.89
substernalC38.1C78.1–D15.2D38.3D49.89

Patient EducationClinical

Chest Injuries and Disorders

The chest is the part of your body between your neck and your abdomen (belly). The medical term for your chest is thorax.

The full article covers:

  • What is the chest?
  • What are chest injuries and disorders?
  • How are chest injuries and disorders diagnosed?

Read the full article at MedlinePlus

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

Convert D38.3 to ICD-9-CMHistory

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

ICD-9-CM
235.8 Unc behav neo pleura
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 2017–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About D38.3Overview

What is the ICD-10 code for neoplasm of uncertain behavior of mediastinum?

The ICD-10-CM code for neoplasm of uncertain behavior of mediastinum is D38.3 (sometimes written as D383). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

Is D38.3 a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report neoplasm of uncertain behavior of mediastinum on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

What MS-DRG does D38.3 group to?

When neoplasm of uncertain behavior of mediastinum is the principal diagnosis on an inpatient stay, it groups to MS-DRG 181, 180, 182, with relative weights from 0.7436 to 1.7800 depending on complications. Higher weights mean higher Medicare reimbursement.

Can D38.3 be reported with D48.7?

Not as a rule. The Excludes1 note at D38, which applies to D38.3, lists "neoplasm of uncertain behavior of heart (D48.7)". 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 is the ICD-9 equivalent of D38.3?

Under the General Equivalence Mappings, neoplasm of uncertain behavior of mediastinum converts to ICD-9-CM 235.8 (unc behav neo pleura). The mapping is approximate, so confirm the match fits the documentation.