ICD-10 Code C40.20 – Malignant neoplasm of long bones of unspecified lower limb (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code C40.20 – Malignant neoplasm of long bones of unspecified lower limb
What it is
C40.20 identifies a malignant neoplasm arising in a long bone of the lower limb when the specific bone is not documented. Use it for primary bone cancer in the leg or foot region, not for metastases.
Clinical signs
Clinical features vary; refer to documentation. Commonly recorded findings include persistent localized bone pain, swelling, tenderness, or a mass in the affected limb, with imaging or biopsy supporting malignancy.
When to use this code
Use this code when the provider documents a primary malignant tumor in a long bone of the lower extremity but does not specify the exact bone. It is appropriate when records say “long bone of lower limb” or similar wording. If the site is later clarified, code the more specific diagnosis.
Do not use for
Do not use C40.20 for metastatic bone disease, benign bone tumors, or malignancies in bones outside the lower limb. Check documentation if the site is unclear or if the tumor involves a different skeletal location.
Coding tip
Code the exact anatomic site only when documented; otherwise, C40.20 is the correct unspecified lower-limb long-bone choice.