2027 ICD-10-CM Diagnosis Code C49.A4Gastrointestinal stromal tumor of large intestine

ICD-10-CM Codes›C00–D49›C45-C49›C49

ICD-10-CM C49.A4
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

C49.A4 is a billable ICD-10-CM diagnosis code for gastrointestinal stromal tumor of large intestine. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 374 through 376. As a secondary diagnosis, it counts as a complication or comorbidity (CC) and moves an inpatient stay to a higher severity level within its MS-DRG family. It does not count, however, when the principal diagnosis is one of 2 closely related codes. Coders also document this condition as gastrointestinal stromal neoplasm of colon. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Gastrointestinal cancers - colorectal.

For Medicare Advantage risk adjustment, C49.A4 maps to CMS-HCC Category 23 (Prostate, Breast, and Other Cancers and Tumors) under the V28 model, adding a risk factor of about 0.186 for a community, non-dual, aged beneficiary in payment year 2027.

Code Identity

ICD-10-CM Code
C49.A4
Billable Status
Yes — Valid for Submission
Code Describes
Gastrointestinal stromal tumor of large intestine
Short Description
Gastrointestinal stromal tumor of large intestine
Same as the full description in the CMS dataset.
Parent Code
C49.A
Gastrointestinal stromal tumor

Code Classification

ChapterC00–D49Neoplasms
SectionC45-C49Malignant neoplasms of mesothelial and soft tissue
CategoryC49Malignant neoplasm of other connective and soft tissue
This CodeC49.A4Gastrointestinal stromal tumor of large intestine

Medicare Risk Adjustment (HCC)Billing

C49.A4 maps to a payment category in the CMS-HCC model used to risk-adjust Medicare Advantage payments. Weights are the published community factors for payment year 2027.

CMS-HCC V28 Category (Payment Model)
HCC 23— Prostate, Breast, and Other Cancers and Tumors
Payment HCC · PY 2027 one of 234 ICD-10-CM codes in this category
Risk Adjustment Factor (RAF) Weight
+0.186
community, non-dual, aged · ranges 0.186–0.237 across segments
Hierarchy
Superseded by HCC 17, HCC 18, HCC 19, HCC 20, HCC 21, and HCC 22
a more severe related category takes the payment when both are reported
Prior Model (CMS-HCC V24)
HCC 10
V24 retired V28 pays 100% of MA risk scores since PY 2026
Other CMS Models
PACE (CMS-HCC V22): HCC 10 · ESRD (V21): HCC 10 · ESRD (V24): HCC 10
ESRD V21 weights: 0.136 dialysis, 0.451–0.668 functioning graft · ESRD V24 weights: 0.111 dialysis, 0.467–0.780 functioning graft
Part D (RxHCC)
RxHCC 20 — Lung, Kidney, and Other Cancers; Secondary Cancer of Lymph Nodes and Other Sites
also risk-adjusts in the Part D prescription drug model (V08)

Source: CMS Payment Year 2027 risk adjustment mappings and model software. Weights are relative factors, not dollar amounts; a beneficiary's total RAF also includes demographics and interactions. Browse all CMS-HCC categories.

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Gastrointestinal stromal neoplasm of colon
  • Gastrointestinal stromal tumor of appendix
  • Gastrointestinal stromal tumor of large intestine
  • Primary malignant gastrointestinal stromal neoplasm of colon
  • Primary malignant mesenchymal neoplasm of colon

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to C49.A4: its own notes plus those printed at C49 and Chapter 2. A note printed at a category, block or chapter applies to every code under it.

Includes

Further defines, or gives examples of, the content of the category.

From C49 Malignant neoplasm of other connective and soft tissue applies to 20 codes
  • malignant neoplasm of blood vessel
  • malignant neoplasm of bursa
  • malignant neoplasm of cartilage
  • malignant neoplasm of fascia
  • malignant neoplasm of fat
  • malignant neoplasm of ligament, except uterine
  • malignant neoplasm of lymphatic vessel
  • malignant neoplasm of muscle
  • malignant neoplasm of synovia
  • malignant neoplasm of tendon (sheath)

Excludes1

Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.

From C49 Malignant neoplasm of other connective and soft tissue applies to 20 codes
  • malignant neoplasm of cartilage (of):
  • articular (C40-C41)
  • larynx (C32.3)
  • nose (C30.0)
  • malignant neoplasm of connective tissue of breast (C50.-)

Excludes2

Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.

From C49 Malignant neoplasm of other connective and soft tissue applies to 20 codes
  • Kaposi's sarcoma of soft tissue (C46.1)
  • malignant neoplasm of heart (C38.0)
  • malignant neoplasm of peripheral nerves and autonomic nervous system (C47.-)
  • malignant neoplasm of peritoneum (C48.2)
  • malignant neoplasm of retroperitoneum (C48.0)
  • malignant neoplasm of uterine ligament (C57.3)
  • mesothelioma (C45.-)

Notes

General instructions on how these codes are used.

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 C49.A4, its category, or a range that includes it.

Applicable To 1

These notes mention C49.A4.

  • Z85.83 Personal history of malignant neoplasm of bone and soft tissue
    Conditions classifiable to C40-C41; C45-C49 names C45-C49, which includes this code

Excludes1 1

These codes carry an Excludes1 note naming C49.A4: they are not reported together with it, unless the two conditions are unrelated.

  • Block C40-C41 Malignant neoplasms of bone and articular cartilage
    malignant neoplasm of synovia (C49.-) names C49.-, which includes this code

Excludes2 1

These codes carry an Excludes2 note naming C49.A4: its condition is not part of those codes, and both may be reported when the patient has both.

  • Block C15-C26 Malignant neoplasms of digestive organs
    gastrointestinal stromal tumors (C49.A-) names C49.A-, which includes this code

Code First 1

These codes say to code first a condition named in the note, and C49.A4 is one of the conditions named.

  • M63 Disorders of muscle in diseases classified elsewhere
    neoplasm (C49.-, C79.89, D21.-, D48.1-) names C49.-, which includes this code

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 NEO015
Gastrointestinal cancers - colorectal
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Colorectal Gastrointestinal Stromal Tumor

    a gastrointestinal stromal tumor that arises from the colon or rectum. the majority of cases have spindle cell morphology.

  • Gastrointestinal Stromal Tumors

    all tumors in the gastrointestinal tract arising from mesenchymal cells (mesoderm) except those of smooth muscle cells (leiomyoma) or schwann cells (schwannoma).

Patient EducationClinical

Gastrointestinal stromal tumor

A gastrointestinal stromal tumor (GIST) is a type of tumor that occurs in the gastrointestinal tract, most commonly in the stomach or small intestine. This type of tumor is thought to grow from specialized cells found in the gastrointestinal tract called interstitial cells of Cajal (ICCs) or precursors to these cells.

Read the full article at MedlinePlus

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

Convert C49.A4 to ICD-9-CMHistory

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

ICD-9-CM
171.5 Mal neo soft tis abdomen
Approximate The match is approximate rather than exact.

Code History & ChangesHistory

Replacement C49.A4 replaces the following previously assigned code(s):

  • C49.4 - Malignant neoplasm of connective and soft tissue of abdomen
FY 2019AddedAdded to the ICD-10-CM code setEffective October 1, 2018.
FY 2020–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About C49.A4Overview

What is the ICD-10 code for gastrointestinal stromal tumor of large intestine?

The ICD-10-CM code for gastrointestinal stromal tumor of large intestine is C49.A4 (sometimes written as C49A4). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

Is C49.A4 (Gastrointestinal stromal tumor) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report gastrointestinal stromal tumor of large intestine on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

What MS-DRG does C49.A4 group to?

When gastrointestinal stromal tumor of large intestine is the principal diagnosis on an inpatient stay, it groups to MS-DRG 375, 374, 376, with relative weights from 0.8925 to 2.1101 depending on complications. Higher weights mean higher Medicare reimbursement.

Is C49.A4 a CC or MCC?

CMS lists C49.A4 as a CC (complication or comorbidity) for FY 2027. Reported as a secondary diagnosis, it moves the inpatient stay to a higher-weighted DRG within its severity family. It does not count when the principal diagnosis is one of the 2 closely related codes in its exclusion list.

Can C49.A4 be reported with C32.3?

Not as a rule. The Excludes1 note at C49, which applies to C49.A4, lists "larynx (C32.3)". 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 HCC is C49.A4?

C49.A4 (gastrointestinal stromal tumor of large intestine) maps to CMS-HCC Category 23 (Prostate, Breast, and Other Cancers and Tumors), commonly written as HCC 23, in the CMS-HCC V28 model used for Medicare Advantage risk adjustment in payment year 2027. It mapped to HCC 10 under the retired V24 model. It also maps in the PACE (CMS-HCC V22), ESRD (V21), and ESRD (V24) models. In the Part D prescription drug model it maps to RxHCC 20.

Does C49.A4 risk-adjust for Medicare Advantage payment?

Yes. When documented and reported on a Medicare Advantage encounter, C49.A4 adds a risk adjustment factor of about 0.186 to the beneficiary's RAF score for a community, non-dual, aged enrollee (published V28 weights range from 0.186 to 0.237 depending on the payment segment). A more severe related category (HCC 17, HCC 18, HCC 19, HCC 20, HCC 21, and HCC 22) supersedes it when both are reported. See the full factor table on the HCC 23 category page.