What is ICD-10 code C40.10?

C40.10 is the ICD-10-CM diagnosis code for Malignant neoplasm of short bones of unspecified upper limb. Cancer that starts in the small bones of the upper arm or hand when the specific side (right or left) is not documented or specified. C40.10 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. C40.10 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. C40.10 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. C40.10 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.

Which HCC does C40.10 map to under V28?

C40.10 maps to CMS-HCC V28 HCC 21 (Lymphoma and Other Cancers). The category numbers, labels, and conditions come from the CMS-HCC V28 model file for payment year 2026.

2026 ICD-10-CM C40.10: Malignant neoplasm of short

C40.10 maps to CMS-HCC V28 21. A source-labeled RAF reference is available. Confirm the documented diagnosis and applicable coding requirements. MEAT criteria · RAF Calculator · HCC coding software

ICD-10-CM Code View

HCC Buddy Code Card

Digital ICD-10 code-book layout with official code detail, always-visible risk models, Code Trumping, and Buddy coding guidance.

Code lookupC40.10

Effective periodFY2026 Apr Update (Apr 1-Sep 30)

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

C40.10

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

Malignant neoplasm of short bones of unspecified upper limb

Cancer that starts in the small bones of the upper arm or hand when the specific side (right or left) is not documented or specified.

Buddy Insight

Primary malignant neoplasm of the short bones (carpals, metacarpals) of an unspecified upper limb.

Overview Risk Models Code Book Documentation Audit Notes Edition comparison

CMS-HCC V28

Mapped

HCC 21

Lymphoma and Other Cancers

Code-level coefficient reference

CMS-HCC V24

Historical

Not used for standard CY2026 Medicare Advantage payment. Select a historical period to review V24.

Not used for CY2026 payment

ACA/HHS

Mapped

HCC 010

HHS-HCC 010 adult, RAF varies...

Code-level coefficient reference

ESRD/PACE

Mapped

HCC 10

Lymphoma and Other Cancers

Code-level coefficient reference

RXHCC

Mapped

HCC 22

Prostate, Breast, Bladder, an...

Code-level coefficient reference

Code Book Path

Official

C40Malignant neoplasm of bone and articular cartilage of limbs C40.1Malignant neoplasm of short bones of upper limb C40.10Malignant neoplasm of short bones of unspecified upper limb

Inclusion Terms

Official

No inclusion terms are included in this display for C40.10. Check the code and parent instructions in the Code Book.

Excludes 2

Official

No Excludes 2 notes are included in this display for C40.10. Check the code and parent instructions in the Code Book.

Related Codes

Official

C40.11Malignant neoplasm of short bones of right upper limb C40.12Malignant neoplasm of short bones of left upper limb

Includes

Official

malignant neoplasm of cartilage (articular) (joint)Inherited from C40-C41
malignant neoplasm of periosteumInherited from C40-C41

Excludes 1

Official

malignant neoplasm of bone marrow NOS (C96.9)Inherited from C40-C41
malignant neoplasm of synovia (C49.-)Inherited from C40-C41

Code First

Official

No Code First sequencing instructions are included in this display for C40.10. Check the code and parent instructions in the Code Book.

Use Additional

Official

code to identify major osseous defect, if applicable (M89.7-)Inherited from C40

Code Also

Official

No Code Also instructions are included in this display for C40.10. Check the code and parent instructions in the Code Book.

Buddy Documentation Tip

HCC Buddy guidance

Attempt to clarify laterality (right vs. left) through provider query

Specific short bone involved (carpal bones, metacarpals, or phalanges)

Histologic type confirmed by biopsy or pathology

Primary vs. metastatic origin confirmed

MEAT Support

HCC Buddy guidance

Attempt to clarify laterality (right vs. left) through provider query

Specific short bone involved (carpal bones, metacarpals, or phalanges)

Histologic type confirmed by biopsy or pathology

Primary vs. metastatic origin confirmed

Audit Caution

HCC Buddy guidance

Defaulting to unspecified laterality when the record contains laterality information elsewhere in the note

Confusing short bones (carpals, metacarpals) with long bones (humerus, radius, ulna) — these have different code axes

Missing the distinction between primary bone malignancy and metastatic disease from soft tissue sarcomas of the hand

Not querying the provider for laterality when it is reasonably determinable from imaging or operative reports

Common Mistakes

HCC Buddy guidance

C40.11 — Short bones of RIGHT upper limb; use when right side is documented

C40.12 — Short bones of LEFT upper limb; use when left side is documented

C40.00 — Long bones of unspecified upper limb; distinguish short bones (hand/wrist) from long bones (humerus/radius/ulna)

C79.51 — Secondary malignant neoplasm of bone; for metastatic disease to these bones

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 C40.10 an HCC code?

Yes. C40.10 (Malignant neoplasm of short bones of unspecified upper limb) maps to HCC 21, Lymphoma and Other Cancers under the CMS-HCC V28 risk adjustment model, with a source-labeled community non-dual aged reference coefficient of 0.671. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes. It is billable for payment year 2026.

Coder answer: C40.10 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: C40.10
Description: Malignant neoplasm of short bones of unspecified upper limb
HCC (V28): HCC 21 — Lymphoma and Other Cancers
RAF reference coefficient: 0.671
Billable: Yes
Payment year: 2026

HCC Category Mapping

V28HCC 21, Lymphoma and Other Cancers

0.671

ESRDHCC 10, Lymphoma and Other Cancers

Not separately weighted

RxHCCHCC 22, Prostate, Breast, Bladder, and Other Cancers and Tumors

Not separately weighted

These are source-labeled model coefficients, not member totals. A category may still be removed by hierarchy or model cleanup rules. 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 context, hierarchy and cleanup rules, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains available for historical review.

Work C40.10 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →

MEAT review for C40.10

For C40.10, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule.

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

Coder workflow notes

Get the V28 mapping + MEAT cheat sheet

One printable reference: check representative V28 mappings and the documentation reminders your note needs. Free, no card.

Free PDF. No card. Unsubscribe anytime.

What This Code Means

C40.10 is the ICD-10-CM diagnosis code for malignant neoplasm of short bones of unspecified upper limb. Cancer that starts in the small bones of the upper arm or hand when the specific side (right or left) is not documented or specified. C40.10 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, C40.10 maps to Lymphoma and Other Cancers (HCC 21) with a source-labeled community, non-dual, aged reference coefficient of 0.671. No V24 mapping is shown for C40.10; use the applicable model and payment year when reviewing the V28 mapping. For CY2026 non-PACE Medicare Advantage, CMS uses 100% of the 2024 CMS-HCC model (V28). PACE uses a separate model blend. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes.

Use this code only when laterality cannot be determined from medical record; always attempt to clarify which side is affected. For C40.10, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule. 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, source-labeled coefficient references, and MEAT documentation criteria for C40.10 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•Use this code only when laterality cannot be determined from medical record; always attempt to clarify which side is affected
•Short bones of upper limb include carpal and metacarpal bones; ensure distinction from long bone involvement

Clinical Significance

Primary malignant neoplasm of the short bones (carpals, metacarpals) of an unspecified upper limb. Short bone cancers of the hand and wrist are uncommon and often present late with swelling and pain. The unspecified laterality designation should prompt a provider query, as laterality directly affects surgical planning and coding specificity.

Documentation Requirements

✓Attempt to clarify laterality (right vs. left) through provider query
✓Specific short bone involved (carpal bones, metacarpals, or phalanges)
✓Histologic type confirmed by biopsy or pathology
✓Primary vs. metastatic origin confirmed
✓Current treatment status and plan
✓Reason laterality is unspecified (e.g., outside records, imaging pending)

Commonly Confused Codes

•C40.11: Short bones of RIGHT upper limb; use when right side is documented
•C40.12: Short bones of LEFT upper limb; use when left side is documented
•C40.00: Long bones of unspecified upper limb; distinguish short bones (hand/wrist) from long bones (humerus/radius/ulna)
•C79.51: Secondary malignant neoplasm of bone; for metastatic disease to these bones