C79.31 (Secondary malignant neoplasm of brain) compared with D43.2 (Neoplasm of uncertain behavior of brain, unspecified), from the official CMS tabular data. C79.31 and D43.2 name the same anatomical site (brain) with a different neoplasm behavior. MedCoder-derived
Same anatomical site, different neoplasm behavior.
Same site — uncertain behavior (brain)
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. C79.31 and D43.2 name the same anatomical site (brain) 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.
| C79.31Secondary malignant neoplasm of brain | D43.2Neoplasm of uncertain behavior of brain, unspecified | |
|---|---|---|
| Billing status | Billable | Billable |
| Classification | C00-D49 — Neoplasms | C00-D49 — Neoplasms |
| Definition | Secondary malignant neoplasm of brain is a billable ICD-10-CM diagnosis code (C79.31). | Neoplasm of uncertain behavior of brain, unspecified is a billable ICD-10-CM diagnosis code (D43.2). |
Derived from the official CMS ICD-10-CM tabular data (FY2026). Not billing advice; verify sequencing rules for the encounter. All data sources