ICD10BillableValid for clinical use
ICD-10 Code C79.9: Secondary malignant neoplasm of unspecified site
Reviewed by HealthAssure Clinical TeamUpdated 26 May 2026
What is this code?
ICD-10 codes are diagnosis classification codes used in healthcare records, reporting, coding workflows, and billing support. This code sits within the broader ICD-10 area for Neoplasms (C00-D49).
When is it used?
- May be used when a clinician documents secondary malignant neoplasm of unspecified site in a patient's medical record.
- May appear in hospital records, claims, referrals, and clinical documentation.
- This code can be used as a clinically usable diagnosis entry in standardized coding workflows.
What it does not mean
- A code alone does not explain severity, treatment plan, or outcome.
- A medical code should not be treated as a substitute for a doctor's diagnosis or advice.
Code hierarchy
chapter
2Neoplasms (C00-D49)
block
C00-C96Malignant neoplasms
block
C76-C80Malignant neoplasms of ill-defined, other secondary and unspecified sites
category
C79Secondary malignant neoplasm of other and unspecified sites
currentC79
Official coding notes
Inclusion terms
- Metastatic cancer NOS
- Metastatic disease NOS
Excludes1 (do not code together)
- carcinomatosis NOS (C80.0)
- generalized cancer NOS (C80.0)
- malignant (primary) neoplasm of unspecified site (C80.1)
Where you may see this code
You may see this code in hospital records, discharge summaries, insurance claims, encounter documentation, referrals, or other healthcare billing and coding records.
Related specialists
OncologistGeneral Physician
Related codes
C79.0Secondary malignant neoplasm of kidney and renal pelviscategoryC79.1Secondary malignant neoplasm of bladder and other and unspecified urinary organscategoryC79.2Secondary malignant neoplasm of skincodeC79.3Secondary malignant neoplasm of brain and cerebral meningescategoryC79.4Secondary malignant neoplasm of other and unspecified parts of nervous systemcategoryC79.5Secondary malignant neoplasm of bone and bone marrowcategoryC79.6Secondary malignant neoplasm of ovarycategoryC79.7Secondary malignant neoplasm of adrenal glandcategoryC79.8Secondary malignant neoplasm of other specified sitescategory
Sibling codes
C79.0Secondary malignant neoplasm of kidney and renal pelvisC79.1Secondary malignant neoplasm of bladder and other and unspecified urinary organsC79.2Secondary malignant neoplasm of skinbillableC79.3Secondary malignant neoplasm of brain and cerebral meningesC79.4Secondary malignant neoplasm of other and unspecified parts of nervous systemC79.5Secondary malignant neoplasm of bone and bone marrowC79.6Secondary malignant neoplasm of ovaryC79.7Secondary malignant neoplasm of adrenal glandC79.8Secondary malignant neoplasm of other specified sites
Coverage-related procedures and services
CPT 81162high
BRCA1 (BRCA1, DNA REPAIR ASSOCIATED), BRCA2 (BRCA2, DNA REPAIR ASSOCIATED) (EG, HEREDITARY BREAST AND OVARIAN CANCER) GENE ANALYSIS; FULL SEQUENCE ANALYSIS AND FULL DUPLICATION/DELETION ANALYSIS (IE, DETECTION OF LARGE GENE REARRANGEMENTS)
Source: CMS coverage guidance
CPT 81540high
ONCOLOGY (TUMOR OF UNKNOWN ORIGIN), MRNA, GENE EXPRESSION PROFILING BY REAL-TIME RT-PCR OF 92 GENES (87 CONTENT AND 5 HOUSEKEEPING) TO CLASSIFY TUMOR INTO MAIN CANCER TYPE AND SUBTYPE, UTILIZING FORMALIN-FIXED PARAFFIN-EMBEDDED TISSUE, ALGORITHM REPORTED AS A PROBABILITY OF A PREDICTED MAIN CANCER TYPE AND SUBTYPE
Source: CMS coverage guidance
CPT 81479high
UNLISTED MOLECULAR PATHOLOGY PROCEDURE
Source: CMS coverage guidance
CPT 76376high
3D RENDERING WITH INTERPRETATION AND REPORTING OF COMPUTED TOMOGRAPHY, MAGNETIC RESONANCE IMAGING, ULTRASOUND, OR OTHER TOMOGRAPHIC MODALITY WITH IMAGE POSTPROCESSING UNDER CONCURRENT SUPERVISION; NOT REQUIRING IMAGE POSTPROCESSING ON AN INDEPENDENT WORKSTATION
Source: CMS coverage guidance
CPT 76377high
3D RENDERING WITH INTERPRETATION AND REPORTING OF COMPUTED TOMOGRAPHY, MAGNETIC RESONANCE IMAGING, ULTRASOUND, OR OTHER TOMOGRAPHIC MODALITY WITH IMAGE POSTPROCESSING UNDER CONCURRENT SUPERVISION; REQUIRING IMAGE POSTPROCESSING ON AN INDEPENDENT WORKSTATION
Source: CMS coverage guidance
CPT 93325high
DOPPLER ECHOCARDIOGRAPHY COLOR FLOW VELOCITY MAPPING (LIST SEPARATELY IN ADDITION TO CODES FOR ECHOCARDIOGRAPHY)
Source: CMS coverage guidance
Mapped diagnoses and classifications
SNOMED_CT 423595004high
Adenocarcinoma carcinomatosis
Source: SNOMED International ICD-10 map
SNOMED_CT 307593001high
Carcinomatosis
Source: SNOMED International ICD-10 map
SNOMED_CT 720587009high
Donor derived melanoma
Source: SNOMED International ICD-10 map
SNOMED_CT 1254749009high
Metastatic acantholytic squamous cell carcinoma
Source: SNOMED International ICD-10 map
SNOMED_CT 354081000119101high
Metastatic adenocarcinoma
Source: SNOMED International ICD-10 map
SNOMED_CT 1264116009high
Metastatic adenosquamous carcinoma
Source: SNOMED International ICD-10 map
Coding guidelines
Compatibility
Legacy and official ICD code match exactly.
Legacy codes
C79.9
Common synonyms
Secondary malignant neoplasm of unspecified siteSecondary malignant neoplasm of site
Frequently asked questions
About this content
This page is prepared by HealthAssure's clinical team using official coding standards from ICD-10. AI tools assist with drafting explanations, which are then reviewed and verified by healthcare professionals for accuracy. This content is for informational purposes and does not replace professional medical advice. Meet our team.