C40.2 (Malignant neoplasm of long bones of lower limb) compared with C79.51 (Secondary malignant neoplasm of bone), from the official CMS tabular data. C40.2 and C79.51 name the same anatomical site (bone) with a different neoplasm behavior. MedCoder-derived
Same anatomical site, different neoplasm behavior.
Same site — secondary malignancy (bone)
The behavior documented for the site — malignant primary, secondary, carcinoma in situ, benign, uncertain or unspecified — decides which column of the neoplasm table, and therefore which code, applies.
Source: CMS Table of Neoplasms
Same site, different neoplasm behavior. C40.2 and C79.51 name the same anatomical site (bone) with a different neoplasm behavior.
From the CMS/CDC Table of Neoplasms: the behavior documented for that site — malignant primary, secondary, carcinoma in situ, benign, uncertain or unspecified — decides which column, and therefore which code, applies.
| C40.2Malignant neoplasm of long bones of lower limb | C79.51Secondary malignant neoplasm of bone | |
|---|---|---|
| Billing status | Non-billable header | Billable |
| Classification | C00-D49 — Neoplasms | C00-D49 — Neoplasms |
| Definition | Malignant neoplasm of long bones of lower limb is a non-billable ICD-10-CM category code (C40.2). | Secondary malignant neoplasm of bone is a billable ICD-10-CM diagnosis code (C79.51). |
| Includes | malignant neoplasm of cartilage (articular) (joint) malignant neoplasm of periosteum | — |
| Use additional code | code to identify major osseous defect, if applicable (M89.7-) | — |
Derived from the official CMS ICD-10-CM tabular data (FY2026). Not billing advice; verify sequencing rules for the encounter. All data sources