What is ICD-10 code C40.90?

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 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. C40.90 is part of the FY2026 ICD-10-CM code set published by the CMS National Center for Health Statistics and used on Medicare, Medicaid, and commercial claims in the United States.

Yes. C40.90 is a billable ICD-10-CM code that can be reported on professional and institutional claims as a primary or secondary diagnosis when the provider documentation supports the specific condition described. Billable codes in ICD-10-CM are coded to the highest level of specificity available for the documented diagnosis. C40.90 is current for fiscal year 2026 and remains in the active CMS ICD-10-CM code set published by the National Center for Health Statistics.

What is the V28 vs V24 difference for C40.90?

CMS phased in the V28 risk adjustment model over payment years 2024 (33%), 2025 (67%), and 2026 (100%), replacing V24. V28 consolidates HCC categories, removes some lower-acuity conditions, and recalibrates RAF weights across the entire model. For C40.90, V28 maps to Lymphoma and Other Cancers at RAF 0.671 while V24 mapped to Lymphoma and Other Cancers at RAF 0.675. Both models can still appear in legacy data and in payer-specific lookback periods.

What should coders know when reporting C40.90?

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 Because C40.90 maps to a payment HCC, the documentation must also satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's risk adjustment score.

2026 ICD-10-CM C40.90: Malignant neoplasm

ICD-10-CM Code View

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Code lookupC40.90Effective periodFY2026 Apr Update (Apr 1-Sep 30)

FY 2026 Apr update / Neoplasms (C00-D49) / Malignant neoplasms of bone and articular cartilage (C40-C41)

C40.90

Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidance

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.

Buddy Insight

Primary malignant neoplasm of unspecified bones and articular cartilage of an unspecified limb.

CMS-HCC V28

Mapped

HCC 21

Lymphoma and Other Cancers

RAF 0.671

CMS-HCC V24

Mapped

HCC 10

Lymphoma and Other Cancers

RAF 0.675

ACA/HHS

Mapped

HCC 10

HHS-HCC 10

Varies by metal level

ESRD/PACE

Mapped

HCC 10

Lymphoma and Other Cancers

RAF 0.111

RXHCC

Mapped

HCC 22

Cancer, Other Specified Sites

RAF 0.124

Code Book Path

Official

C40Malignant neoplasm of bone and articular cartilage of limbs

C40.9Malignant neoplasm of unspecified bones and articular cartilage of limb

C40.90Malignant neoplasm of unspecified bones and articular cartilage of unspecified limb

Inclusion Terms

Official

ICD-10-CM does not list inclusion terms for C40.90 in this effective period.

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for C40.90 in this effective period.

Related Child Codes

Official

C40.91Malignant neoplasm of unspecified bones and articular cartilage of right limb

C40.92Malignant neoplasm of unspecified bones and articular cartilage of left limb

Includes

Official

ICD-10-CM does not list Includes notes for C40.90 in this effective period.

Excludes 1

Official

ICD-10-CM does not list Excludes 1 notes for C40.90 in this effective period.

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for C40.90 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for C40.90 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for C40.90 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance

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

MEAT Support

HCC Buddy guidance

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

Audit Caution

HCC Buddy guidance

Using this maximally unspecified code when more details are available elsewhere in the record

Not querying the provider when imaging or pathology reports contain site-specific information

Confusing this with C41.9 which covers unspecified bone malignancy NOT limited to limbs

Failing to update the code once additional diagnostic information becomes available

Common Mistakes

HCC Buddy guidance

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

Current with CMS: FY2026 ICD-10-CM Apr 1 update (effective Apr 1 – Sep 30, 2026) · CMS-HCC V28, 100% phased in for payment year 2026. FY2027 code set already staged for October 1, 2026. How HCC Buddy stays current →

Is C40.90 an HCC code?

Yes. C40.90 (Malignant neoplasm of unspecified bones and articular cartilage of unspecified limb) maps to Lymphoma and Other Cancers under the CMS-HCC V28 risk adjustment model (and Lymphoma and Other Cancers under V24), with a community non-dual aged RAF of 0.671. It is billable for payment year 2026.

Coder answer: C40.90 is billable and maps to V28 HCC 21, Lymphoma and Other Cancers. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.

Code: C40.90
Description: Malignant neoplasm of unspecified bones and articular cartilage of unspecified limb
HCC (V28): HCC 21 — Lymphoma and Other Cancers
RAF: 0.671
Billable: Yes
Payment year: 2026

HCC Category Mapping

V28HCC 21, Lymphoma and Other Cancers

0.671

V24HCC 10, Lymphoma and Other Cancers

0.675

ESRDHCC 10, Lymphoma and Other Cancers

0.111

RxHCCHCC 22, Cancer, Other Specified Sites

0.124

Each model's RAF is its CMS base weight for that model's standard population, so weights are not directly comparable across models: CMS-HCC V28 and V24 use Community, Non-Dual, Aged; ESRD uses the dialysis continuing-enrollee model; RxHCC is the Part D continuing-enrollee, non-low-income, aged weight (a larger scale than CMS-HCC). ACA/HHS has no single weight — it varies by metal level. 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.

Work C40.90 in the Code Book — tabular path, V28 RAF, and MEAT checklist →

MEAT Criteria for C40.90

For C40.90 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 C40.90 during that encounter, not just copy-forwarded from a problem list.

Coder workflow notes

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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