C17.9
BillableMalignant neoplasm of small intestine, unspecified
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is C17.9 an HCC code?
Yes. C17.9 maps to Lung and Other Severe Cancers under the CMS-HCC V28 risk adjustment model (and Lung and Other Severe Cancers under V24).
HCC Category Mapping
RAF weights shown are the community, non-dual, aged base weights from the CMS risk adjustment model file. 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.
MEAT Criteria for C17.9
For C17.9 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 C17.9 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
C17.9 is the ICD-10-CM diagnosis code for malignant neoplasm of small intestine, unspecified. This code represents cancer that has developed in the small intestine, but the specific location within the small intestine (duodenum, jejunum, or ileum) has not been identified or documented. It is used when a patient has been diagnosed with small intestine cancer without more specific anatomical detail. C17.9 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, C17.9 maps to Lung and Other Severe Cancers (HCC 20) with a community, non-dual, aged base RAF weight of 0.000. Under the older V24 model, C17.9 mapped to the same category but with a base RAF weight of 0.973 — 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.
Query the physician if the specific site of the small intestine cancer is documented in the medical record, as codes C17.0 (duodenum), C17.1 (jejunum), and C17.2 (ileum) provide more specificity and may affect treatment planning and staging. Because C17.9 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 C17.9 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Query the physician if the specific site of the small intestine cancer is documented in the medical record, as codes C17.0 (duodenum), C17.1 (jejunum), and C17.2 (ileum) provide more specificity and may affect treatment planning and staging
- •Ensure this code is used only when the site is truly unspecified; review pathology reports and imaging studies which often document the exact location of the malignancy
Clinical Significance
Unspecified small intestine cancer is used when documentation confirms malignancy but does not identify which segment (duodenum, jejunum, or ileum) is involved. Small bowel cancers are rare overall, accounting for less than 5% of gastrointestinal malignancies, but carry significant morbidity. While this code captures the appropriate HCC, documentation improvement efforts should aim to identify the specific segment from surgical, pathological, or imaging records.
Documentation Requirements
- ✓Confirmed malignancy of the small intestine
- ✓Review of all available records (pathology, operative notes, imaging) for segment identification before defaulting to unspecified
- ✓Histological type if known
- ✓Stage of disease
- ✓Treatment status
Commonly Confused Codes
- •C17.0-C17.2 — Specific small intestine segments: always use the more specific code when documentation supports it
- •C17.8 — Overlapping sites: use when tumor is known to span multiple segments, not when location is unknown
- •C26.0 — Intestinal tract, part unspecified: even broader unspecified code; use C17.9 when small intestine is confirmed but segment is not
- •D37.2 — Neoplasm of uncertain behavior of small intestine: different behavior classification; confirm malignancy