C80.0 ICD-10-CM Code: Disseminated malignant neoplasm, unspecified
C80.0 maps to CMS-HCC V28 18 (RAF 2.341). Documentation must support MEAT. MEAT criteria · RAF calculator · HCC coding software
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FY 2026 Apr update / Neoplasms (C00-D49) / Malignant neoplasms of ill-defined, other secondary and unspecified sites (C76-C80)
C80.0
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceDisseminated malignant neoplasm, unspecified
Cancer that has spread throughout the body in multiple locations, but the original source or type cannot be determined.
Buddy Insight
Disseminated malignant neoplasm, unspecified represents widespread cancer throughout the body where neither the primary site nor the specific cancer type can be determined.
CMS-HCC V28
MappedHCC 18
RAF 2.341
CMS-HCC V24
MappedHCC 8
RAF 2.659
ACA/HHS
MappedHCC 8
Varies by metal level
ESRD/PACE
MappedHCC 8
RAF 0.353
RXHCC
MappedHCC 20
RAF 0.491
Code Book Path
Inclusion Terms
Official- Carcinomatosis NOS
- Generalized cancer, unspecified site (primary) (secondary)
- Generalized malignancy, unspecified site (primary) (secondary)
Excludes 2
OfficialICD-10-CM does not list Excludes 2 notes for C80.0 in this effective period.
Related Child Codes
Includes
OfficialICD-10-CM does not list Includes notes for C80.0 in this effective period.
Excludes 1
Official- malignant carcinoid tumor of unspecified site (C7A.00)
- malignant neoplasm of specified multiple sites- code to each site
Code First
OfficialICD-10-CM does not list Code First sequencing instructions for C80.0 in this effective period.
Use Additional
OfficialICD-10-CM does not list Use Additional Code instructions for C80.0 in this effective period.
Code Also
OfficialICD-10-CM does not list Code Also instructions for C80.0 in this effective period.
Buddy Documentation Tip
MEAT Support
Audit Caution
Common Mistakes
Current with CMS: FY2026 ICD-10-CM Apr 1 update (effective Apr 1 – Sep 30, 2026) · CMS-HCC V28, 100% phased in for payment year 2026. FY2027 code set already staged for October 1, 2026. How HCC Buddy stays current →
Is C80.0 an HCC code?
Yes. C80.0 (Disseminated malignant neoplasm, unspecified) maps to Cancer Metastatic to Bone, Other and Unspecified Metastatic Cancer; Acute Leukemia Except Myeloid under the CMS-HCC V28 risk adjustment model (and Metastatic Cancer and Acute Leukemia under V24), with a community non-dual aged RAF of 2.341. It is billable for payment year 2026.
Coder answer: C80.0 is billable and maps to V28 HCC 18, Cancer Metastatic to Bone, Other and Unspecified Metastatic Cancer; Acute Leukemia Except Myeloid. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.
- Code
- C80.0
- Description
- Disseminated malignant neoplasm, unspecified
- HCC (V28)
- HCC 18 — Cancer Metastatic to Bone, Other and Unspecified Metastatic Cancer; Acute Leukemia Except Myeloid
- RAF
- 2.341
- Billable
- Yes
- Payment year
- 2026
HCC Category Mapping
Each model's RAF is its CMS base weight for that model's standard population, so weights are not directly comparable across models: CMS-HCC V28 and V24 use Community, Non-Dual, Aged; ESRD uses the dialysis continuing-enrollee model; RxHCC is the Part D continuing-enrollee, non-low-income, aged weight (a larger scale than CMS-HCC). ACA/HHS has no single weight — it varies by metal level. Actual per-patient RAF contribution depends on member segment, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains in use during the transition and for historical data.
Work C80.0 in the Code Book — tabular path, V28 RAF, and MEAT checklist →
MEAT Criteria for C80.0
For C80.0 to count as a valid HCC diagnosis in a given encounter, the provider's documentation must show MEAT: Monitor, Evaluate, Assess, or Treat. A diagnosis from a prior year does not carry forward automatically, it has to be re-documented and supported each calendar year.
- MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
- EEvaluate: test results, medication response, or physical findings reviewed by the provider
- AAssess: explicit mention in the assessment or plan with acknowledgment of status
- TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis
Only one of M/E/A/T is required to support the code, but the documentation must be specific enough to show that the provider actually addressed C80.0 during that encounter, not just copy-forwarded from a problem list.
Coder workflow notes
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What This Code Means
C80.0 is the ICD-10-CM diagnosis code for disseminated malignant neoplasm, unspecified. Cancer that has spread throughout the body in multiple locations, but the original source or type cannot be determined. C80.0 sits in the ICD-10-CM chapter for neoplasms (c00-d49), within the section covering malignant neoplasms of ill-defined, other secondary and unspecified sites (c76-c80).
Under the CMS-HCC V28 risk adjustment model, C80.0 maps to Cancer Metastatic to Bone, Other and Unspecified Metastatic Cancer; Acute Leukemia Except Myeloid (HCC 18) with a community, non-dual, aged base RAF weight of 2.341. Under the older CMS-HCC V24 model, C80.0 maps to Metastatic Cancer and Acute Leukemia (HCC 8) with a community, non-dual, aged base RAF weight of 2.659. V28 is the CMS-HCC risk adjustment model that reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition.
Use only when disseminated cancer is documented but primary site is unknown or unspecified. Because C80.0 maps to a payment HCC, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's Medicare Advantage risk adjustment score. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for C80.0 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Use only when disseminated cancer is documented but primary site is unknown or unspecified
- •This is a non-specific code; attempt to identify primary site before using this code
Clinical Significance
Disseminated malignant neoplasm, unspecified represents widespread cancer throughout the body where neither the primary site nor the specific cancer type can be determined. This diagnosis carries an extremely poor prognosis and reflects a patient with high care needs including pain management, nutritional support, and often palliative or hospice-level services. It indicates that despite diagnostic workup, the cancer origin remains unknown.
Documentation Requirements
- ✓Documentation confirming disseminated (widespread) malignancy
- ✓Record of diagnostic workup performed to attempt to identify primary site and cancer type
- ✓Explanation for why the primary site cannot be determined (cancer of unknown primary)
- ✓Sites of metastatic disease documented
- ✓Performance status and treatment plan (curative intent vs palliative)
- ✓Palliative care or hospice referral documentation if applicable
Commonly Confused Codes
- •C80.1: Malignant (primary) neoplasm, unspecified: Use C80.1 for primary cancer of unknown site without confirmed dissemination; C80.0 specifically indicates widespread metastatic disease
- •C79 series: Secondary malignant neoplasm codes: Use when specific metastatic sites can be identified even if primary is unknown
- •C76 series: Malignant neoplasm of other and ill-defined sites: Use when a general body region is known but not the specific organ