What is ICD-10 code C17.8?

C17.8 is the ICD-10-CM diagnosis code for Malignant neoplasm of overlapping sites of small intestine. Cancer involving multiple overlapping sites within the small intestine rather than being limited to one section. It belongs to the ICD-10-CM chapter for neoplasms (c00-d49). C17.8 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. C17.8 is part of the FY2026 ICD-10-CM code set published by the CMS National Center for Health Statistics and used on Medicare, Medicaid, and commercial claims in the United States.

Yes. C17.8 is a billable ICD-10-CM code that can be reported on professional and institutional claims as a primary or secondary diagnosis when the provider documentation supports the specific condition described. Billable codes in ICD-10-CM are coded to the highest level of specificity available for the documented diagnosis. C17.8 is current for fiscal year 2026 and remains in the active CMS ICD-10-CM code set published by the National Center for Health Statistics.

What is the V28 vs V24 difference for C17.8?

CMS phased in the V28 risk adjustment model over payment years 2024 (33%), 2025 (67%), and 2026 (100%), replacing V24. V28 consolidates HCC categories, removes some lower-acuity conditions, and recalibrates RAF weights across the entire model. For C17.8, V28 maps to Lung and Other Severe Cancers at RAF 1.136 while V24 mapped to Lung and Other Severe Cancers at RAF 1.024. Both models can still appear in legacy data and in payer-specific lookback periods.

What should coders know when reporting C17.8?

Specify which sections of small intestine are involved (duodenum, jejunum, ileum) in documentation Overlapping involvement suggests more extensive disease requiring comprehensive staging Because C17.8 maps to a payment HCC, the documentation must also satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's risk adjustment score.

2026 ICD-10-CM C17.8: Malignant neoplasm

ICD-10-CM Code View

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Code lookupC17.8Effective periodFY2026 Apr Update (Apr 1-Sep 30)

FY 2026 Apr update / Neoplasms (C00-D49) / Malignant neoplasms of digestive organs (C15-C26)

C17.8

Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidance

Malignant neoplasm of overlapping sites of small intestine

Cancer involving multiple overlapping sites within the small intestine rather than being limited to one section.

Buddy Insight

Overlapping sites of the small intestine indicates a malignant tumor spanning multiple segments (duodenum, jejunum, ileum), reflecting more extensive disease.

CMS-HCC V28

Mapped

HCC 20

Lung and Other Severe Cancers

RAF 1.136

CMS-HCC V24

Mapped

HCC 9

Lung and Other Severe Cancers

RAF 1.024

ACA/HHS

Mapped

HCC 9

HHS-HCC 9

Varies by metal level

ESRD/PACE

Mapped

HCC 9

Lung and Other Severe Cancers

RAF 0.181

RXHCC

Mapped

HCC 22

Cancer, Other Specified Sites

RAF 0.124

Code Book Path

Official

C17Malignant neoplasm of small intestine

C17.8Malignant neoplasm of overlapping sites of small intestine

Inclusion Terms

Official

ICD-10-CM does not list inclusion terms for C17.8 in this effective period.

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for C17.8 in this effective period.

Related Child Codes

Official

C17.0Malignant neoplasm of duodenum

C17.1Malignant neoplasm of jejunum

C17.2Malignant neoplasm of ileum

C17.3Meckel's diverticulum, malignant

C17.9Malignant neoplasm of small intestine, unspecified

Includes

Official

ICD-10-CM does not list Includes notes for C17.8 in this effective period.

Excludes 1

Official

malignant carcinoid tumors of the small intestine (C7A.01)

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for C17.8 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for C17.8 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for C17.8 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance

Documentation confirming the tumor involves two or more distinct segments of the small intestine

Identification of the specific segments involved

Histological type

Confirmation this is a single primary tumor spanning segments, not multiple separate primaries

MEAT Support

HCC Buddy guidance

Documentation confirming the tumor involves two or more distinct segments of the small intestine

Identification of the specific segments involved

Histological type

Confirmation this is a single primary tumor spanning segments, not multiple separate primaries

Audit Caution

HCC Buddy guidance

Using C17.8 when the location is simply unknown — that requires C17.9 (unspecified)

Coding as overlapping when documentation only mentions one segment with possible extension into an adjacent area

Confusing overlapping sites with multifocal disease — overlapping means one tumor crossing boundaries, not multiple separate tumors

Common Mistakes

HCC Buddy guidance

C17.9 — Small intestine, unspecified: C17.8 is for known multi-segment disease; C17.9 is for unknown location

C17.0-C17.2 — Specific small intestine segments: use site-specific code when tumor is confined to one segment

C18.8 — Overlapping sites of colon: if the tumor extends from small intestine into colon, code the primary origin

Current with CMS: FY2026 ICD-10-CM Apr 1 update (effective Apr 1 – Sep 30, 2026) · CMS-HCC V28, 100% phased in for payment year 2026. FY2027 code set already staged for October 1, 2026. How HCC Buddy stays current →

Is C17.8 an HCC code?

Yes. C17.8 (Malignant neoplasm of overlapping sites of small intestine) maps to Lung and Other Severe Cancers under the CMS-HCC V28 risk adjustment model (and Lung and Other Severe Cancers under V24), with a community non-dual aged RAF of 1.136. It is billable for payment year 2026.

Coder answer: C17.8 is billable and maps to V28 HCC 20, Lung and Other Severe Cancers. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.

Code: C17.8
Description: Malignant neoplasm of overlapping sites of small intestine
HCC (V28): HCC 20 — Lung and Other Severe Cancers
RAF: 1.136
Billable: Yes
Payment year: 2026

HCC Category Mapping

V28HCC 20, Lung and Other Severe Cancers

1.136

V24HCC 9, Lung and Other Severe Cancers

1.024

ESRDHCC 9, Lung and Other Severe Cancers

0.181

RxHCCHCC 22, Cancer, Other Specified Sites

0.124

Each model's RAF is its CMS base weight for that model's standard population, so weights are not directly comparable across models: CMS-HCC V28 and V24 use Community, Non-Dual, Aged; ESRD uses the dialysis continuing-enrollee model; RxHCC is the Part D continuing-enrollee, non-low-income, aged weight (a larger scale than CMS-HCC). ACA/HHS has no single weight — it varies by metal level. Actual per-patient RAF contribution depends on member segment, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains in use during the transition and for historical data.

Work C17.8 in the Code Book — tabular path, V28 RAF, and MEAT checklist →

MEAT Criteria for C17.8

For C17.8 to count as a valid HCC diagnosis in a given encounter, the provider's documentation must show MEAT: Monitor, Evaluate, Assess, or Treat. A diagnosis from a prior year does not carry forward automatically, it has to be re-documented and supported each calendar year.

MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
EEvaluate: test results, medication response, or physical findings reviewed by the provider
AAssess: explicit mention in the assessment or plan with acknowledgment of status
TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis

Only one of M/E/A/T is required to support the code, but the documentation must be specific enough to show that the provider actually addressed C17.8 during that encounter, not just copy-forwarded from a problem list.

Coder workflow notes

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What This Code Means

C17.8 is the ICD-10-CM diagnosis code for malignant neoplasm of overlapping sites of small intestine. Cancer involving multiple overlapping sites within the small intestine rather than being limited to one section. C17.8 sits in the ICD-10-CM chapter for neoplasms (c00-d49), within the section covering malignant neoplasms of digestive organs (c15-c26).

Under the CMS-HCC V28 risk adjustment model, C17.8 maps to Lung and Other Severe Cancers (HCC 20) with a community, non-dual, aged base RAF weight of 1.136. Under the older V24 model, C17.8 mapped to the same category but with a base RAF weight of 1.024, V28 recalibrated weights across the entire model. V28 is the CMS-HCC risk adjustment model that reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition.

Specify which sections of small intestine are involved (duodenum, jejunum, ileum) in documentation. Because C17.8 maps to a payment HCC, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's Medicare Advantage risk adjustment score. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.

HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for C17.8 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•Specify which sections of small intestine are involved (duodenum, jejunum, ileum) in documentation
•Overlapping involvement suggests more extensive disease requiring comprehensive staging

Clinical Significance

Overlapping sites of the small intestine indicates a malignant tumor spanning multiple segments (duodenum, jejunum, ileum), reflecting more extensive disease. These tumors are generally associated with a worse prognosis due to their size and extent, often requiring more extensive surgical resection. Accurate coding of overlapping versus single-site disease is important for both risk adjustment and clinical research tracking of advanced small bowel malignancies.

Documentation Requirements

✓Documentation confirming the tumor involves two or more distinct segments of the small intestine
✓Identification of the specific segments involved
✓Histological type
✓Confirmation this is a single primary tumor spanning segments, not multiple separate primaries
✓Stage of disease and extent of resection

Commonly Confused Codes

•C17.9: Small intestine, unspecified: C17.8 is for known multi-segment disease; C17.9 is for unknown location
•C17.0-C17.2: Specific small intestine segments: use site-specific code when tumor is confined to one segment
•C18.8: Overlapping sites of colon: if the tumor extends from small intestine into colon, code the primary origin