C46.1
BillableKaposi's sarcoma of soft tissue
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is C46.1 an HCC code?
Yes. C46.1 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 C46.1
For C46.1 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 C46.1 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
C46.1 is the ICD-10-CM diagnosis code for kaposi's sarcoma of soft tissue. A cancer of blood vessel cells in soft tissues (muscles, fat, connective tissue) that can occur internally or superficially. C46.1 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, C46.1 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, C46.1 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.
Soft tissue Kaposi's sarcoma may involve multiple anatomical sites; document all involved areas and whether lesions are localized or disseminated. Because C46.1 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 C46.1 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Soft tissue Kaposi's sarcoma may involve multiple anatomical sites; document all involved areas and whether lesions are localized or disseminated
- •Distinguish from skin-only involvement (C46.0) by confirming involvement of deeper soft tissue structures
Clinical Significance
Kaposi sarcoma of soft tissue indicates deeper tissue involvement beyond the skin surface, suggesting more advanced or aggressive disease. This distinction from cutaneous-only disease is clinically significant because soft tissue involvement often requires more intensive treatment and indicates a worse prognosis.
Documentation Requirements
- ✓Pathology confirmation of Kaposi sarcoma in soft tissue structures (muscle, fat, connective tissue)
- ✓Distinction from skin-only disease — documentation must specify deeper tissue involvement
- ✓Underlying immunodeficiency status and current treatment
- ✓Imaging studies confirming soft tissue mass or infiltration
- ✓Assessment of extent of disease (localized versus disseminated)
Excludes 2 — Not included here, may code separately
- Kaposi's sarcoma of lymph glands and nodes (C46.3)