2026 ICD-10-CM Diagnosis Code C16.1Malignant neoplasm of fundus of stomach
ICD-10-CM Codes›C00–D49›C15-C26›C16
- Billable — Valid for Submission
- CC — Complication or Comorbidity
- Risk Adjusts — HCC 20
- Chronic Condition
C16.1 is a billable ICD-10-CM diagnosis code for malignant neoplasm of fundus of stomach. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) 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 32 closely related codes. Coders also document this condition as carcinoma of fundus of stomach. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Gastrointestinal cancers - stomach.
For Medicare Advantage risk adjustment, C16.1 maps to CMS-HCC Category 20 (Lung and Other Severe Cancers) under the V28 model, adding a risk factor of about 1.136 for a community, non-dual, aged beneficiary in payment year 2026.
Code Identity
Code Classification
Medicare Risk Adjustment (HCC)Billing
C16.1 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 2026.
Source: CMS Payment Year 2026 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.
- Carcinoma of fundus of stomach
- Leiomyosarcoma of fundus of stomach
- Leiomyosarcoma of stomach
- Lymphoma of fundus of stomach
- Malignant neoplasm of fundus of stomach
- Primary adenocarcinoma of fundus of stomach
- Primary carcinoma of fundus of stomach
- Primary malignant neoplasm of fundus of stomach
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Table of NeoplasmsClinical
Patient EducationClinical
Stomach Cancer
The stomach is an organ between the esophagus and the small intestine. It mixes food with stomach acid and helps digest protein. Stomach cancer mostly affects older people - two-thirds of people who have it are over age 65. Your risk of getting it is also higher if you:
The full article covers:
- What is Stomach Cancer?
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert C16.1 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About C16.1Overview
What is the ICD-10 code for malignant neoplasm of fundus of stomach?
The ICD-10-CM code for malignant neoplasm of fundus of stomach is C16.1 (sometimes written as C161). It is billable on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
Is C16.1 (Malignant neoplasm of stomach) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report malignant neoplasm of fundus of stomach on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What MS-DRG does C16.1 group to?
When malignant neoplasm of fundus of stomach is the principal diagnosis on an inpatient stay, it groups to MS-DRG 374, 375, 376, with relative weights from 0.9243 to 2.1387 depending on complications. Higher weights mean higher Medicare reimbursement.
Is C16.1 a CC or MCC?
CMS lists C16.1 as a CC (complication or comorbidity) for FY 2026. 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 32 closely related codes in its exclusion list.
What is the ICD-9 equivalent of C16.1?
Under the General Equivalence Mappings, malignant neoplasm of fundus of stomach converts to ICD-9-CM 151.3 (mal neo stomach fundus). The mapping is a direct match.
What HCC is C16.1?
C16.1 (malignant neoplasm of fundus of stomach) maps to CMS-HCC Category 20 (Lung and Other Severe Cancers), commonly written as HCC 20, in the CMS-HCC V28 model used for Medicare Advantage risk adjustment in payment year 2026. It mapped to HCC 9 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 22.
Does C16.1 risk-adjust for Medicare Advantage payment?
Yes. When documented and reported on a Medicare Advantage encounter, C16.1 adds a risk adjustment factor of about 1.136 to the beneficiary's RAF score for a community, non-dual, aged enrollee (published V28 weights range from 0.672 to 1.214 depending on the payment segment). A more severe related category (HCC 17, HCC 18, and HCC 19) supersedes it when both are reported. See the full factor table on the HCC 20 category page.
