C72.9 vs C79.40

C72.9 (Malignant neoplasm of central nervous system, unspecified) compared with C79.40 (Secondary malignant neoplasm of unspecified part of nervous system), from the official CMS tabular data. C72.9 and C79.40 name the same anatomical site (central nervous system) with a different neoplasm behavior. MedCoder-derived

Relationship

Informational

Neoplasm table relationship

C72.9

Malignant neoplasm of central nervous system, unspecified

↔

C79.40

Secondary malignant neoplasm of unspecified part of nervous system

Same anatomical site, different neoplasm behavior.

Same site — secondary malignancy (central nervous system)

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

Can these codes be reported together?

Same site, different neoplasm behavior. C72.9 and C79.40 name the same anatomical site (central nervous system) 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.

Side by side

	C72.9Malignant neoplasm of central nervous system, unspecified	C79.40Secondary malignant neoplasm of unspecified part of nervous system
Billing status	Billable	Billable
Classification	C00-D49 — Neoplasms (C00-D49)	C00-D49 — Neoplasms (C00-D49)
Definition	Malignant neoplasm of central nervous system, unspecified is a billable ICD-10-CM diagnosis code (C72.9).	Secondary malignant neoplasm of unspecified part of nervous system is a billable ICD-10-CM diagnosis code (C79.40).
Includes	Malignant neoplasm of unspecified site of central nervous system Malignant neoplasm of nervous system NOS	—

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Derived from the official CMS ICD-10-CM tabular data (FY2026). Not billing advice; verify sequencing rules for the encounter. All data sources