C17.3
BillableMeckel's diverticulum, malignant
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is C17.3 an HCC code?
Yes. C17.3 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 C17.3
For C17.3 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 C17.3 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
C17.3 is the ICD-10-CM diagnosis code for meckel's diverticulum, malignant. This is a rare cancer that develops in Meckel's diverticulum, which is a small pouch-like remnant of tissue in the small intestine that some people are born with. The malignant tumor in this location requires specific coding to identify both the cancer and its unusual site. C17.3 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, C17.3 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, C17.3 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.
Verify documentation confirms malignancy in Meckel's diverticulum specifically, as this is a rare condition; do not confuse with benign Meckel's diverticulum (Q43.0). Because C17.3 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 C17.3 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Verify documentation confirms malignancy in Meckel's diverticulum specifically, as this is a rare condition; do not confuse with benign Meckel's diverticulum (Q43.0)
- •Ensure the histological type of the malignancy is documented separately if available, as additional codes may be needed to specify the cancer type (e.g., carcinoid, adenocarcinoma)
Clinical Significance
Malignant Meckel diverticulum is an extremely rare cancer arising in a congenital remnant of the omphalomesenteric duct in the small intestine. This code is uniquely specific because it identifies both the malignant nature and the unusual anatomical origin. The rarity of this diagnosis makes accurate coding critical, as it affects both clinical research data and appropriate risk adjustment for an uncommon condition requiring complex surgical management.
Documentation Requirements
- ✓Documentation confirming both the presence of Meckel diverticulum and malignancy within it
- ✓Histological type of the malignancy (carcinoid, adenocarcinoma, sarcoma)
- ✓Pathological confirmation of malignancy (not just presence of Meckel diverticulum)
- ✓Stage of disease and extent of surgical resection
- ✓Distinction from benign Meckel diverticulum
Excludes 1 — Do NOT code together
- Meckel's diverticulum, congenital (Q43.0)
Commonly Confused Codes
- •Q43.0 — Meckel diverticulum (displaced/persistent): congenital anomaly without malignancy; do not confuse benign with malignant
- •C17.2 — Malignant neoplasm of ileum: if the tumor is in the ileum near but not within a Meckel diverticulum, use ileum code
- •C17.8 — Overlapping sites of small intestine: if the tumor extends beyond the diverticulum into the ileum