2027 ICD-10-CM Diagnosis Code C40.31Malignant neoplasm of short bones of right lower limb
ICD-10-CM Codes›C00–D49›C40-C41›C40
- Billable — Valid for Submission
- CC — Complication or Comorbidity
- Risk Adjusts — HCC 21
- Chronic Condition
C40.31 is a billable ICD-10-CM diagnosis code for malignant neoplasm of short bones of right lower limb. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 542 through 544. As a secondary diagnosis, it counts as a complication or comorbidity (CC) and moves an inpatient stay to a higher severity level within its MS-DRG family. It does not count, however, when the principal diagnosis is one of 11 closely related codes. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Bone cancer.
For Medicare Advantage risk adjustment, C40.31 maps to CMS-HCC Category 21 (Lymphoma and Other Cancers) under the V28 model, adding a risk factor of about 0.671 for a community, non-dual, aged beneficiary in payment year 2027.
Code Identity
Code Classification
Medicare Risk Adjustment (HCC)Billing
C40.31 maps to a payment category in the CMS-HCC model used to risk-adjust Medicare Advantage payments. Weights are the published community factors for payment year 2027.
Source: CMS Payment Year 2027 risk adjustment mappings and model software. Weights are relative factors, not dollar amounts; a beneficiary's total RAF also includes demographics and interactions. Browse all CMS-HCC categories.
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Neoplasm of bone of right foot
- Primary chondrosarcoma of bone of lower limb
- Primary chondrosarcoma of bone of right foot
- Primary chondrosarcoma of bone of right lower limb
- Primary Ewing sarcoma of bone of right foot
- Primary Ewing sarcoma of bone of right lower limb
- Primary malignant neoplasm of bone of right foot
- Primary malignant neoplasm of bone of right lower limb
- Primary osteosarcoma of bone of right foot
- Primary osteosarcoma of bone of right lower limb
- Sarcoma of bone of foot
Instructional NotesGuidance
Instructions from the official ICD-10-CM Tabular List that apply to C40.31: its own notes plus those printed at C40, block C40-C41, and Chapter 2. A note printed at a category, block or chapter applies to every code under it.
Includes
Further defines, or gives examples of, the content of the category.
- malignant neoplasm of cartilage (articular) (joint)
- malignant neoplasm of periosteum
Excludes1
Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.
Use Additional Code
Add a second code, after this one, to fully describe the condition.
Notes
General instructions on how these codes are used.
- Functional activity
- All neoplasms are classified in this chapter, whether they are functionally active or not. An additional code from Chapter 4 may be used, to identify functional activity associated with any neoplasm.
- Morphology [Histology]
- Chapter 2 classifies neoplasms primarily by site (topography), with broad groupings for behavior, malignant, in situ, benign, etc. The Table of Neoplasms should be used to identify the correct topography code. In a few cases, such as for malignant melanoma and certain neuroendocrine tumors, the morphology (histologic type) is included in the category and codes.
- Primary malignant neoplasms overlapping site boundaries
- A primary malignant neoplasm that overlaps two or more contiguous (next to each other) sites should be classified to the subcategory/code .8 ('overlapping lesion'), unless the combination is specifically indexed elsewhere. For multiple neoplasms of the same site that are not contiguous, such as tumors in different quadrants of the same breast, codes for each site should be assigned.
- Malignant neoplasm of ectopic tissue
- Malignant neoplasms of ectopic tissue are to be coded to the site mentioned, e.g., ectopic pancreatic malignant neoplasms are coded to pancreas, unspecified (C25.9).
Source: CMS ICD-10-CM Tabular List. How to read instructional notes.
Referenced in Other NotesGuidance
Instructional notes printed at other codes that name C40.31, its category, or a range that includes it.
Applicable To 1
These notes mention C40.31.
- Z85.83 Personal history of malignant neoplasm of bone and soft tissue
Excludes1 3
These codes carry an Excludes1 note naming C40.31: they are not reported together with it, unless the two conditions are unrelated.
- C41 Malignant neoplasm of bone and articular cartilage of other and unspecified sitesmalignant neoplasm of bones of limbs (C40.-) names C40.-, which includes this code
- C41 Malignant neoplasm of bone and articular cartilage of other and unspecified sitesmalignant neoplasm of cartilage of limbs (C40.-) names C40.-, which includes this code
- C49 Malignant neoplasm of other connective and soft tissue
Code First 2
These codes say to code first a condition named in the note, and C40.31 is one of the conditions named.
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Table of NeoplasmsClinical
Anatomical sites in the Table of Neoplasms that reference this code family.
| Site | Malig. Primary | Malig. Secondary | Ca in situ | Benign | Uncertain | Unspec. |
|---|---|---|---|---|---|---|
| bone (periosteum) › ankle | C40.3 | C79.51 | – | D16.3 | – | – |
| bone (periosteum) › astragalus | C40.3 | C79.51 | – | D16.3 | – | – |
| bone (periosteum) › calcaneus | C40.3 | C79.51 | – | D16.3 | – | – |
| bone (periosteum) › cuboid | C40.3 | C79.51 | – | D16.3 | – | – |
| bone (periosteum) › foot | C40.3 | C79.51 | – | D16.3 | – | – |
| bone (periosteum) › heel | C40.3 | C79.51 | – | D16.3 | – | – |
| bone (periosteum) › limb NEC › lower (long bones) › short bones | C40.3 | C79.51 | – | D16.3 | – | – |
| bone (periosteum) › metatarsus (any) | C40.3 | C79.51 | – | D16.3 | – | – |
| bone (periosteum) › navicular › ankle | C40.3 | C79.51 | – | – | – | – |
| bone (periosteum) › phalanges › foot | C40.3 | C79.51 | – | – | – | – |
| bone (periosteum) › scaphoid › of ankle | C40.3 | C79.51 | – | – | – | – |
| bone (periosteum) › tarsus (any) | C40.3 | C79.51 | – | – | – | – |
| bone (periosteum) › toe (any) | C40.3 | C79.51 | – | – | – | – |
| metatarsus (any bone) | C40.3 | C79.51 | – | D16.3 | – | – |
| phalanges › foot | C40.3 | C79.51 | – | D16.3 | – | – |
| tarsus (any bone) | C40.3 | C79.51 | – | D16.3 | – | – |
Patient EducationClinical
Bone Cancer
Cancer that starts in a bone is uncommon. Cancer that has spread to the bone from another part of the body is more common.
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert C40.31 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About C40.31Overview
What is the ICD-10 code for malignant neoplasm of short bones of right lower limb?
The ICD-10-CM code for malignant neoplasm of short bones of right lower limb is C40.31 (sometimes written as C4031). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
Is C40.31 (Malignant neoplasm of short bones of lower limb) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report malignant neoplasm of short bones of right lower limb on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
What MS-DRG does C40.31 group to?
When malignant neoplasm of short bones of right lower limb is the principal diagnosis on an inpatient stay, it groups to MS-DRG 543, 544, 542, with relative weights from 0.7404 to 1.7208 depending on complications. Higher weights mean higher Medicare reimbursement.
Is C40.31 a CC or MCC?
CMS lists C40.31 as a CC (complication or comorbidity) for FY 2027. Reported as a secondary diagnosis, it moves the inpatient stay to a higher-weighted DRG within its severity family. It does not count when the principal diagnosis is one of the 11 closely related codes in its exclusion list.
Can C40.31 be reported with C96.9?
Not as a rule. The Excludes1 note at block C40-C41, which applies to C40.31, lists "malignant neoplasm of bone marrow NOS (C96.9)". An Excludes1 note means the excluded code is never reported together with this one; the only exception is when the two conditions are unrelated to each other (Official Guidelines, Section I.A.12.a).
What HCC is C40.31?
C40.31 (malignant neoplasm of short bones of right lower limb) maps to CMS-HCC Category 21 (Lymphoma and Other Cancers), commonly written as HCC 21, in the CMS-HCC V28 model used for Medicare Advantage risk adjustment in payment year 2027. It mapped to HCC 10 under the retired V24 model. It also maps in the PACE (CMS-HCC V22), ESRD (V21), and ESRD (V24) models. In the Part D prescription drug model it maps to RxHCC 22.
Does C40.31 risk-adjust for Medicare Advantage payment?
Yes. When documented and reported on a Medicare Advantage encounter, C40.31 adds a risk adjustment factor of about 0.671 to the beneficiary's RAF score for a community, non-dual, aged enrollee (published V28 weights range from 0.493 to 0.739 depending on the payment segment). A more severe related category (HCC 17, HCC 18, HCC 19, and HCC 20) supersedes it when both are reported. See the full factor table on the HCC 21 category page.
