C49.9
BillableMalignant neoplasm of connective and soft tissue, unspecified
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is C49.9 an HCC code?
Yes. C49.9 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 C49.9
For C49.9 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 C49.9 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
C49.9 is the ICD-10-CM diagnosis code for malignant neoplasm of connective and soft tissue, unspecified. A malignant tumor of connective and soft tissue when the specific anatomical location is not documented or cannot be determined. C49.9 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, C49.9 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, C49.9 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.
This is the least specific code in the C49 category; attempt to obtain site information from imaging or pathology reports. Because C49.9 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 C49.9 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •This is the least specific code in the C49 category; attempt to obtain site information from imaging or pathology reports
- •Query the provider for anatomical location to assign a more specific code if possible
Clinical Significance
Malignant neoplasm of connective and soft tissue, unspecified is the least specific soft tissue sarcoma code. Its use should be a last resort and trigger a documentation improvement initiative, as the anatomical site is almost always determinable from imaging, pathology, or operative reports.
Documentation Requirements
- ✓Pathology confirming malignant soft tissue neoplasm
- ✓Evidence that site-specific information was sought but unavailable
- ✓Provider query documentation for anatomical specification
- ✓Treatment status despite unknown primary site
- ✓Oncology consultation notes that may contain site information
Commonly Confused Codes
- •C49.0-C49.5 (Site-specific soft tissue codes) — always preferred when site is documented
- •C49.8 (Overlapping sites) — for tumors spanning multiple known sites
- •C80.1 (Malignant neoplasm, unspecified) — even less specific; at least C49.9 identifies soft tissue origin
- •C49.6 (Trunk, unspecified) — slightly more specific if trunk involvement is known