C79.31 (Secondary malignant neoplasm of brain) compared with D33.1 (Benign neoplasm of brain, infratentorial), from the official CMS tabular data. C79.31 and D33.1 name the same anatomical site (basis pedunculi) with a different neoplasm behavior.
Same anatomical site, different neoplasm behavior.
Same site — benign neoplasm (basis pedunculi)
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 D33.1 name the same anatomical site (basis pedunculi) with a different neoplasm behavior.
From the CMS 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 | D33.1Benign neoplasm of brain, infratentorial | |
|---|---|---|
| Billing status | Billable | Billable |
| Classification | C00-D49 — Neoplasms (C00-D49) | C00-D49 — Neoplasms (C00-D49) |
| Definition | Secondary malignant neoplasm of brain is a billable ICD-10-CM diagnosis code (C79.31). | Benign neoplasm of brain, infratentorial is a billable ICD-10-CM diagnosis code (D33.1). |
| Includes | — | Benign neoplasm of brain stem Benign neoplasm of cerebellum Benign neoplasm of fourth ventricle |
Derived from the official CMS ICD-10-CM tabular data (FY2026). Not billing advice; verify sequencing rules for the encounter. All data sources