ICD-10 Code C79.31 – Secondary malignant neoplasm of brain (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code C79.31 – Secondary malignant neoplasm of brain
What it is
C79.31 identifies metastatic cancer that has spread to the brain from a primary site elsewhere in the body. Use this code when the brain lesion is documented as secondary or metastatic, not primary brain cancer.
Clinical signs
Clinical features vary; refer to documentation. Common findings may include neurologic deficits, headaches, seizures, nausea, or altered mental status when brain involvement is present.
When to use this code
Use C79.31 when the record clearly states secondary malignant neoplasm of the brain, brain metastasis, or metastatic disease to the brain. It also applies when imaging or pathology confirms metastatic brain involvement and the provider links it to cancer spread. Code the primary malignancy separately when documented.
Do not use for
Do not use this code for primary malignant brain tumors or for suspected lesions without confirmation. Check documentation if the record only says “brain mass,” “lesion,” or “metastatic cancer” without specifying the brain.
Coding tip
Confirm the site is the brain and that the malignancy is secondary before assigning C79.31.