ICD-10 Code C79 – Secondary malignant neoplasm of other and unspecified sites (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code C79 – Secondary malignant neoplasm of other and unspecified sites
What it is
C79 identifies metastatic cancer in sites not separately classified elsewhere. Use it when the record documents secondary malignant spread to an unspecified or other site.
Clinical signs
Clinical features vary; refer to documentation. Common findings reflect the involved organ or tissue, and diagnosis is usually supported by imaging, pathology, or specialist assessment.
When to use this code
Use C79 when the provider clearly documents secondary malignant neoplasm and does not name a more specific metastatic site code. It is appropriate for metastatic disease noted in the chart, including “secondary cancer” or “metastasis” to an other/unspecified site. If the primary site is known, code it separately when required by the record.
Do not use for
Do not use C79 for a primary malignancy, a benign tumor, or a history of cancer without active metastatic disease. Check documentation if the site is specific enough for a more precise code.
Coding tip
Code the documented metastatic site as specifically as possible before defaulting to C79.