C79.9 Secondary malignant neoplasm of unspecified site

Billable ICD-10-CM code, FY2026. Acts as a Complication or Comorbidity (CC) as a secondary diagnosis.

Applicable to

• Metastatic cancer NOS
• Metastatic disease NOS

Excludes1 (never code together)

• carcinomatosis NOS (C80.0)
• generalized cancer NOS (C80.0)
• malignant (primary) neoplasm of unspecified site (C80.1)

Applies from C79 Secondary malignant neoplasm of other and unspecified sites

Excludes1 (never code together)

• secondary carcinoid tumors (C7B.-)
• secondary neuroendocrine tumors (C7B.-)

Risk adjustment (HCC)

• CMS-HCC V28: HCC 18 — Cancer Metastatic to Bone, Other and Unspecified Metastatic Cancer; Acute Leukemia Except Myeloid
• CMS-HCC V22: HCC 8 — Metastatic Cancer and Acute Leukemia
• RxHCC V08: HCC 18 — Secondary Cancer of Lung, Liver, Brain, and Other Sites
• ESRD V24: HCC 8

MS-DRG index

Defines the logic of DRG(s) 826-828 in MDC 17.

Approximate ICD-9-CM (GEMs)

• 198.89 Secondary malignant neoplasm of other specified sites (approximate)

Code annotations containing back-references to C79.9

Back-references to C79.9

• Type 1 Excludes: C80.1 Malignant (primary) neoplasm, unspecified ("secondary malignant neoplasm of unspecified site (C79.9)")

Diagnosis Index entries for C79.9

• Disease, diseased › metastatic
• Metastasis, metastatic › disease

Nearby codes

• C79.72 Secondary malignant neoplasm of left adrenal gland
• C79.8 Secondary malignant neoplasm of other specified sites
• C79.81 Secondary malignant neoplasm of breast
• C79.82 Secondary malignant neoplasm of genital organs
• C79.89 Secondary malignant neoplasm of other specified sites
• C79.9 Secondary malignant neoplasm of unspecified site (this code)