C40.90
BillableMalignant neoplasm of unspecified bones and articular cartilage of unspecified limb
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is C40.90 an HCC code?
Yes. C40.90 maps to Lymphoma and Other Cancers 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 C40.90
For C40.90to 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 C40.90 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
C40.90 is the ICD-10-CM diagnosis code for malignant neoplasm of unspecified bones and articular cartilage of unspecified limb. Cancer of bone or cartilage in an unspecified arm or leg when the exact location within that limb is not identified. C40.90 sits in the ICD-10-CM chapter for neoplasms (c00-d49), within the section covering malignant neoplasms of bone and articular cartilage (c40-c41).
Under the CMS-HCC V28 risk adjustment model, C40.90 maps to Lymphoma and Other Cancers (HCC 21) with a community, non-dual, aged base RAF weight of 0.671. Under the older V24 model, C40.90 mapped to the same category but with a base RAF weight of 0.675 — 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.
This is a less specific code; use only when the exact bone or cartilage site cannot be determined. Because C40.90 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 C40.90 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •This is a less specific code; use only when the exact bone or cartilage site cannot be determined
- •Query provider for more specific anatomical location if available in documentation
Clinical Significance
Primary malignant neoplasm of unspecified bones and articular cartilage of an unspecified limb. This is the least specific code in the C40 category and should be used only as a last resort when neither the bone site nor the laterality can be determined. It indicates significant documentation deficiency that should be addressed through provider query.
Documentation Requirements
- ✓Provider query for specific bone location and laterality
- ✓Histologic confirmation of malignancy
- ✓Primary vs. metastatic origin documented
- ✓Any imaging available that might clarify the anatomic site
- ✓Clinical reason why specificity cannot be achieved
- ✓Treatment plan and disease status
Commonly Confused Codes
- •C40.91 — Unspecified bones of RIGHT limb; use when at least laterality is known
- •C40.92 — Unspecified bones of LEFT limb; use when at least laterality is known
- •C41.9 — Malignant neoplasm of bone/cartilage, unspecified; for non-limb bone cancers or when limb vs. axial is unknown
- •C79.51 — Secondary malignant neoplasm of bone; for metastatic bone disease