ICD-10 Code C79.40 – Secondary malignant neoplasm of unspecified part of nervous system (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code C79.40 – Secondary malignant neoplasm of unspecified part of nervous system
What it is
This code identifies metastatic cancer involving the nervous system when the exact site is not documented. Use it when the record states secondary malignant neoplasm of the nervous system without further anatomic detail.
Clinical signs
Clinical features vary; refer to documentation. Findings may reflect mass effect, neurologic deficits, pain, seizures, or other signs of metastatic involvement, depending on the site and extent of disease.
When to use this code
Use C79.40 when the provider documents metastasis to the nervous system but does not specify brain, spinal cord, meninges, or another precise location. It may also fit when the note confirms secondary malignant involvement and the site remains unspecified after review.
Do not infer a more specific code from imaging or history alone unless the provider clearly documents the metastatic site. If the record is ambiguous, check documentation.
Do not use for
Do not use this code for primary nervous system tumors or for metastatic disease with a documented specific site such as brain or meninges. Check documentation if the note names a more precise location.
Coding tip
Always code the most specific metastatic site documented; use C79.40 only when the nervous system site is confirmed but not further identified.