C46.4
BillableKaposi's sarcoma of gastrointestinal sites
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is C46.4 an HCC code?
Yes. C46.4 maps to Breast, Prostate, Colorectal and Other Cancers and Tumors under the CMS-HCC V28 risk adjustment model (and Lymphoma and Other 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 C46.4
For C46.4 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 C46.4 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
C46.4 is the ICD-10-CM diagnosis code for kaposi's sarcoma of gastrointestinal sites. Kaposi's sarcoma is a type of cancer that develops in the blood vessels and tissues lining the digestive system, from the mouth to the rectum. This condition is most commonly seen in people with weakened immune systems, particularly those with HIV/AIDS. C46.4 sits in the ICD-10-CM chapter for neoplasms (c00-d49), within the section covering malignant neoplasms of mesothelial and soft tissue (c45-c49).
Under the CMS-HCC V28 risk adjustment model, C46.4 maps to Breast, Prostate, Colorectal and Other Cancers and Tumors (HCC 21) with a community, non-dual, aged base RAF weight of 0.545. Under the older CMS-HCC V24 model, C46.4 maps to Lymphoma and Other Cancers (HCC 10) with a community, non-dual, aged base RAF weight of 0.675. 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.
Always verify the specific gastrointestinal site affected (esophagus, stomach, colon, etc.) as there may be more specific subcodes available under C46.4x. Because C46.4 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 C46.4 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Always verify the specific gastrointestinal site affected (esophagus, stomach, colon, etc.) as there may be more specific subcodes available under C46.4x
- •This code should be paired with the underlying cause of immunosuppression (such as B20 for HIV disease) to provide complete clinical documentation
Clinical Significance
Kaposi sarcoma of the gastrointestinal tract represents visceral involvement and is associated with more severe disease requiring systemic therapy. Gastrointestinal Kaposi sarcoma can cause bleeding, obstruction, or protein-losing enteropathy, significantly increasing morbidity and healthcare utilization.
Documentation Requirements
- ✓Endoscopy or biopsy-confirmed Kaposi sarcoma in the gastrointestinal tract
- ✓Specific gastrointestinal site (esophagus, stomach, duodenum, colon, etc.)
- ✓Symptoms attributable to gastrointestinal involvement (bleeding, obstruction, weight loss)
- ✓Human Immunodeficiency Virus status and antiretroviral therapy response
- ✓Current oncologic treatment plan